JP2011090108A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device and image forming apparatus which can suppress for various types of paper satisfactory fixability and occurrence of wrinkling of recording papers over a long period. <P>SOLUTION: A control section 63 conveys a piece of paper, on which a line pattern is projected in a width direction by a pattern projector 62, to a fixing nip; measures the shape of the line pattern on paper by means of an area sensor 61; and detects the shape of deformation outside the surface of paper. Based on the amount of maximum deformation obtained by the detected shape of the deformation outside the surface, the amount of deflection adjustment is calculated, and a pressing force adjustment mechanism 67 is controlled by the calculated amount of deflection adjustment, and the fixing roller 42 is deflected. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fixing technique of a fixing device that fixes a toner image or the like on a recording medium.

  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 to a fixing nip portion formed by, for example, a fixing roller and a pressure roller.

  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. 10, both ends of the elastic layer 42b of the fixing roller 42 that is rotationally driven by a drive motor are made thicker than the center, and the shape of the fixing roller 42 is changed to both ends. Further, a fixing device having a so-called “reverse crown shape” having a smaller diameter at the center is described. By making the shape of the fixing roller 42 into an inverted crown shape, the peripheral speed of the end portion having a large outer diameter becomes faster than that of the central portion, and a force for pulling the recording paper in the fixing nip outward in the paper width direction acts. When the recording paper receives such a force pulling outward in the paper width direction, generation of wrinkles can be suppressed.

  Patent Document 2 discloses a technique for measuring a sheet shape during conveyance and stopping the apparatus at an early stage when a conveyance abnormality such as floating is detected.

  However, in the above-described conventional technique, when the fixing roller 42 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 both ends of the fixing roller 42 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 landing roller 42 is almost the same at both ends and the center of the fixing roller 42, and there is a problem that wrinkles of the recording paper cannot be suppressed over time. . Furthermore, there is a problem that wrinkles cannot be sufficiently suppressed in the case of recording paper such as thin paper that tends to cause wrinkles.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a fixing device and an image capable of suppressing good fixing properties and wrinkling of recording paper over a wide range of paper types over time. A forming apparatus is provided.

  According to a first aspect of the present invention, there is provided a driving member having an elastic layer, a driven member that has at least an elastic layer, forms a fixing nip between the driving member and the recording member, and passes through the fixing nip. In the fixing device having a heating means for heating the fixing member, when the driving member or the driven member is pressed toward the fixing nip side, the distance from the rotation center near the center of the driving member to the fixing nip is longer than both ends. Based on the detection results of the deflection forming means for deflecting the driving member or the driven member, the out-of-plane deformation shape detection means for detecting the out-of-plane deformation shape over the entire width of the recording paper at the fixing nip entrance, and the out-of-plane deformation shape detection means. And a control unit that controls a deflection amount of the driving member or the driven member.

  According to a second aspect of the present invention, in the fixing device according to the first aspect, the bend forming means bends the drive member by pressing both ends of the rotation shaft of the drive member toward the fixing nip side.

  According to a third aspect of the invention, there is provided the fixing device according to the first or second aspect, further comprising storage means for storing an appropriate out-of-plane deformation shape of the recording paper, and an appropriate out-of-plane deformation shape stored in the storage means; The amount of deflection is controlled based on the out-of-plane deformation shape detected by the out-of-plane deformation shape detecting means.

  According to a fourth aspect of the present invention, in the fixing device according to any one of the first to third aspects, the control unit controls the heating unit based on a deflection amount.

  According to a fifth aspect of the present invention, there is provided a toner image forming unit that forms a toner image on a recording paper, a fixing unit that fixes a toner image on the recording paper, a storage unit that stores information, and a notification unit that notifies information. An image forming apparatus comprising the fixing device according to any one of claims 1 to 4 as a fixing unit.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the storage unit stores a limit out-of-plane deformation shape that causes wrinkles on the recording paper, and the control unit includes an out-of-plane deformation shape detection unit. It is determined whether or not the detection result has reached an out-of-limit deformed shape, and if so, the notification means notifies that the fixing device is to be replaced.

  According to a seventh aspect of the present invention, in the image forming apparatus according to the fifth or sixth aspect, the storage unit stores a limit out-of-plane deformation shape that causes wrinkles on the recording paper, and the control unit includes the out-of-plane deformation shape. It is characterized in that it is determined whether or not the detection result of the detecting means has reached an out-of-limit deformation shape, and if it has reached, the fixing operation is prohibited.

  The invention according to claim 8 is the image forming apparatus according to any one of claims 5 to 7, wherein the storage unit stores the detection results detected by the out-of-plane deformed shape detection unit in time series, The control means predicts the life of the fixing device based on the detection results stored in time series in the storage means, and if it is predicted that the life of the fixing device is near, the notification means informs that the fixing device is to be replaced. It is characterized by doing.

  According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the fifth to eighth aspects, the storage unit chronologically detects the detection results detected by the out-of-plane deformed shape detection unit for each type of recording paper. The control means calculates a threshold value for increasing the probability of occurrence of wrinkles on the recording paper for each type of recording paper based on the detection results stored in time series in the storage means, and records exceeding the threshold value. When paper is used, the notification means notifies that the probability of occurrence of wrinkles is high.

  According to the present invention, it is possible to suppress good fixability and occurrence of wrinkling of recording paper over a wide range of paper types over time.

1 is a schematic configuration diagram schematically illustrating an apparatus configuration in an example of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a perspective view illustrating a configuration of an intermediate transfer belt. It is a schematic block diagram which shows a fixing device and a control block diagram. FIG. 6 is a view of the periphery of the fixing nip of the fixing device as viewed from the recording paper conveyance direction. FIG. 6 is a diagram illustrating a velocity distribution in a paper width direction at a fixing nip. (A) is AA sectional drawing of FIG. 4 when a fixing roller is bent. (B) is a BB cross-sectional view of FIG. 4 when the fixing roller is bent. It is a control flowchart of deflection amount adjustment. It is a block diagram of a deformation | transformation shape detection means outside a paper surface. (A) is an out-of-plane deformation shape detection result when wrinkles occur. (B) is an out-of-plane deformation shape detection result in a state where wrinkles do not occur. It is a figure which shows the conventional fixing roller.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram schematically showing a device configuration of a printer which is an example of an image forming apparatus according to the present invention. The image forming apparatus 1 shown in this figure is an electrophotographic color image forming apparatus capable of forming a full color image by adopting a tandem method, and includes four image forming units 10 (Y, M, C, Bk). The intermediate transfer belt 20 is juxtaposed along the upper running side. The intermediate transfer belt 20 will be described in detail later with reference to FIG.

  Each image forming unit 10 has the same configuration except for the color of the toner to be handled. In FIG. 1, only the leftmost yellow image forming unit 10Y has a reference numeral attached to a device constituting the unit. That is, each image forming unit 10 includes a photosensitive drum 11 as an image carrier. Around the photosensitive drum 11, a charging unit 12, a developing device 13, a cleaning device 14, and the like are arranged, and further, a primary transfer unit is configured inside the intermediate transfer belt 20 so as to face each photosensitive drum 11. A transfer roller 15 is provided. Further, in this example, each image forming unit is provided with an exposure unit. For example, an exposure unit 16 such as an LED is arranged between the charging unit 12 and the developing device 13 so that optical writing is possible. As the exposure means, it is possible to use an exposure apparatus common to each image forming unit, for example, a laser writing apparatus.

  A transfer roller 31, which is a transfer member, is disposed so as to be opposed to the transfer counter roller 32, which is one of the support members of the intermediate transfer belt 20 and functions as a backup member, with the intermediate transfer belt 20 interposed therebetween. In the drawing of the transfer roller 31, a registration roller pair 54 is disposed on the right side, and a conveyance belt 55 is disposed on the left side. A fixing device 40 is provided on the left side of the transport belt 55. This fixing device 40 is a belt fixing device having a fixing belt 43 stretched between a heating roller 41 as a heating means and a fixing roller 42, and the pressed roller 44 is pressed against the fixing roller 42 with the fixing belt 43 interposed therebetween. It is provided to do.

  In the lower part of the apparatus, a sheet feeding tray 50 for storing the sheet bundle P is disposed, and a pickup roller 51 and a separation feeding roller 52 are provided as sheet feeding means. Further, a conveyance roller 53 is disposed at an appropriate position in the sheet conveyance path indicated by a one-dot chain line in the drawing. Further, although not shown, a paper guide is provided as appropriate. In addition, a manual paper feed unit and a paper reversing unit can be provided as necessary. It is also possible to mount an image reading device (scanner), an automatic document feeder (ADF), or the like.

An image forming operation in the image forming apparatus configured as described above will be briefly described.
The photosensitive drum 11 of the image forming unit 10 is rotationally driven counterclockwise in the figure by a driving unit (not shown), and the surface of the photosensitive drum 11 is uniformly charged to a predetermined polarity by the charging unit 12. The charged photosensitive member surface is irradiated with scanning light from the exposure unit 16, thereby forming an electrostatic latent image on the surface of the photosensitive drum 11. At this time, the image information exposed to each photosensitive drum 11 is single-color image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. Each color toner is applied from the developing device 13 to the electrostatic latent image formed in this way, and visualized as a toner image. Further, the intermediate transfer belt 20 is driven to run in the clockwise direction in the figure, and the respective color toner images are sequentially transferred from the photosensitive drum 11 to the intermediate transfer belt 20 by the action of the primary transfer roller 15 in each image forming unit 10. In this way, the intermediate transfer belt 20 carries a full-color toner image on its surface. Note that a single color image can be formed using any one of the image forming units 10, or a two-color or three-color image can be formed using a plurality of image forming units. In the case of monochrome printing, image formation is performed using the black unit 10Bk on the rightmost side of the drawing among the four image forming units.

  The residual toner adhering to the surface of the photosensitive drum 11 after transferring the toner image is removed from the surface of the photosensitive drum by the cleaning device 14, and then the surface is subjected to the action of a static eliminator (not shown) so that the surface potential is initially set. To prepare for the next image formation.

  On the other hand, the paper is fed from the paper feed tray 50 and is sent out toward the secondary transfer position by the registration roller 54 in timing with the toner image carried on the intermediate transfer belt 20. The toner image on the surface of the intermediate transfer belt is collectively transferred onto the sheet by the transfer roller 31 as the second transfer unit. The sheet on which the toner image has been transferred is sent to the fixing device 40 by the conveying belt 55, and when passing through the fixing device 40, the toner image is fused and fixed to the sheet by heat and pressure. The paper on which the toner image is fixed is discharged to a paper discharge tray (not shown).

FIG. 2 is a perspective view showing the configuration of the intermediate transfer belt 20.
As shown in this figure, the intermediate transfer belt 20 is stretched over a drive roller 21, a driven roller 22, an external stretching roller 23, a transfer counter roller 32, and a transfer guide roller 33. The drive roller 21 is driven by a motor 26. By being driven to rotate, the vehicle travels in the direction of arrow A in the figure. The driven roller 22 applies tension to the intermediate transfer belt 20 by a load applying unit (not shown), and generates a friction conveying force between the driving roller 21 and the intermediate transfer belt 20. As described with reference to FIG. 1, the photosensitive drums 11 of the respective color image forming units are arranged in parallel on the upper traveling side of the intermediate transfer belt 20 which is a belt stretching surface formed by the driving roller 21 and the driven roller 22. A transfer roller 15 as a primary transfer unit is disposed in the loop of the intermediate transfer belt 20 so as to face each photoconductor drum 11.
A transfer roller 31 is disposed below the transfer counter roller 32 and is pressed against the transfer counter roller 32 with the intermediate transfer belt 20 interposed therebetween. A predetermined high voltage is applied to the transfer counter roller 32 from a transfer power source (not shown), and a transfer electric field is formed in the transfer nip with the transfer roller 31 that is electrically grounded. In addition, the transfer roller 31 conveys the sheet with a predetermined pressing force together with the transfer counter roller 32 and the intermediate transfer belt 20. Further, a transfer guide roller 33 is disposed on the back side of the intermediate transfer belt 20 and in the vicinity of the upstream side of the transfer counter roller 32 in the belt rotation direction. The transfer roller 30, the transfer counter roller 31 and the transfer guide roller 32 constitute a secondary transfer unit 30.
As can be seen from FIG. 1, the transfer guide roller 33 is disposed slightly outside the straight line connecting the outer peripheral surfaces of the drive roller 21 and the transfer counter roller 32, and the intermediate transfer belt 20 is moved from the belt inner side to the outer side. It is provided at a position to push it out. Thereby, the arrangement relationship between the transfer facing roller 32 and the transfer roller 30 is sandwiched between the transfer nip formed by the transfer roller 30 and the transfer facing roller 32 after the intermediate transfer belt 20 is wound around the surface of the transfer roller 30, and The arrangement is such that the rear end portion of the paper with respect to the portion sandwiched in the transfer nip is brought close to the surface of the image carrier by the waist of the paper.
Although not shown in FIG. 2, belt cleaning means 24 (FIG. 1) for cleaning the intermediate transfer belt 20 is disposed outside the belt between the transfer counter roller 32 and the external stretching roller 23, and the belt. A backing roller 25 (FIG. 1) corresponding to the cleaning blade of the cleaning means 24 is disposed inside the belt. The paper P is conveyed in the direction of arrow B in the figure, and after the posture of the paper is corrected by the registration roller pair 54, it is conveyed between the transfer roller 31 and the intermediate transfer belt 20, and the toner image on the intermediate transfer belt 20 is transferred. It is electrostatically transferred onto the paper.

FIG. 3 is a schematic configuration diagram showing the fixing device 40 and a control block diagram, and FIG. 4 is a view of the periphery of the fixing nip of the fixing device 40 as viewed from the recording paper conveyance direction.
As described above, the fixing device 40 is a belt fixing device having the fixing belt 43 stretched between the heating roller 41 serving as a heating means and the fixing roller 42. The fixing device 40 is applied to the fixing roller 42 with the fixing belt 43 interposed therebetween. A pressure roller 44 is provided so as to be in pressure contact.

  The fixing roller 42 includes a metal core part 42a made of metal and an elastic layer 42b made of silicon rubber or the like provided on the surface of the metal core part. The pressed roller 44 is also composed of a metal core 44a made of metal and an elastic layer 44b made of silicon rubber or the like provided on the surface of the metal core. The fixing roller 42 is supported so as to be movable in a direction orthogonal to the surface of the paper P. Further, as shown in FIG. 4, a pressing force adjusting mechanism 67 as a bending forming means is in contact with both ends of the cored bar portion 44a of the fixing roller 42, and biases the fixing roller 42 toward the pressed roller side. is doing. Both ends of the cored bar portion of the pressed roller 44 are rotatably attached to side walls (not shown) of the apparatus body via bearings (not shown).

  When the plunger 67a of the pressing force adjusting mechanism 67 is moved to the pressed roller 44 side, both end portions of the cored bar portion 42a of the fixing roller 42 are pressed to the pressed roller 44 side. Initially, the entire fixing roller moves toward the pressed roller and presses the pressed roller 44 uniformly in the width direction. Further, when the plunger 67a of the pressing force adjusting mechanism 67 is moved toward the pressed roller 44 and the fixing roller 42 is moved toward the pressed roller 44, the reaction force of the pressed roller 44 increases. Finally, the fixing roller 42 bends as indicated by a two-point cutting line (C) in the figure. When the amount of movement (pressing force) of the plunger 67a of the pressing force adjusting mechanism 67 increases, the amount of bending of the fixing roller 42 increases. Therefore, the amount of movement (pressing force) of the plunger 67a of the pressing force adjusting mechanism 67 is controlled. The amount of bending of the fixing roller 42 can be controlled. That is, in this embodiment, the pressing force adjusting mechanism 67 functions as a deflection forming unit.

The heating roller 41 as a heating means incorporates a heater 45 such as a halogen lamp in a hollow metal cored bar, and heats the fixing belt 43 from the inside by this radiant heat.
The heating roller 41 is rotationally driven by a drive source (not shown), the fixing roller 42 is rotationally driven through the fixing belt 43, and the pressure-sensitive roller 44 is driven to rotate through the fixing nip. In other words, in the present embodiment, the fixing roller 42 functions as a driving member that transmits the driving force of the driving source to the sheet and applies a conveying force to the sheet, and the pressed roller 44 rotates following the fixing nip. It functions as a driven member.

  An area sensor 61 and a pattern projector 62 are provided in the vicinity of the entrance of the fixing nip. The pattern projector 62 of the present embodiment uses a projector that projects a linear pattern in the paper width direction.

  The control unit 63 controls the entire apparatus, and various devices and sensors are connected. In the figure, only the devices and sensors related to the feature points of the present apparatus are shown. The control unit 63, which is a control unit, includes a CPU, a ROM, a RAM, and the like, and realizes functions of each unit by executing a predetermined program on hardware. As shown in the figure, the control unit 63 calculates an out-of-plane deformation shape in the width direction of the sheet P at the entrance of the fixing nip from the output value of the area sensor 61. That is, in the present embodiment, the control unit 63, the area sensor 61, and the pattern projector 62 constitute an out-of-plane deformed shape detection unit. The control unit 63 is connected to a non-volatile memory 64 serving as storage means, and the non-volatile memory 64 stores a reference out-of-plane deformation shape, a limit out-of-plane deformation shape, and the like obtained in advance by experiments. Yes. The non-volatile memory 64 stores the detected out-of-plane deformed shape in time series for each paper type.

  The control unit 63 controls the pressing force of the pressing force adjusting mechanism 67 to control the amount of bending of the fixing roller 42 and the power source 68 of the heater 45 to control the amount of fixing heat. Furthermore, a speaker 65 and a display unit 66 as notification means are connected to the control unit 63, and predetermined information can be notified to the user by controlling the speaker 65 and the display unit 66.

FIG. 5 shows an out-of-plane deformation shape in the sheet width direction at the fixing nip.
As shown in FIG. 5A, when the fixing nip exhibits a convex velocity distribution in the paper conveyance direction B, an inward velocity vector is generated in the fixing nip with respect to the paper conveyance direction. For this reason, as the paper P is transported through the fixing nip, both end portions in the width direction of the paper P are gradually transported inward, and the possibility that “wrinkles” will eventually occur on the paper increases. On the other hand, as shown in FIG. 5B, when the fixing nip exhibits a concave speed distribution with respect to the paper conveyance direction B, a velocity vector outward from the paper conveyance direction at the fixing nip is obtained. Arise. For this reason, both end portions in the width direction of the paper are pulled outward in the fixing nip, so that the paper is less likely to wrinkle.

  In the present embodiment, in the fixing nip, the fixing roller 42 that transmits a driving force to the sheet is bent in the fixing nip so that a speed distribution as shown in FIG. 5B is obtained. When the fixing roller 42 is bent as shown by the two-point cutting line C in FIG. 4, the central portion of the cored bar portion 42a of the fixing roller 42 is located farther from the pressed roller 44 than both ends. It will be. As a result, the pressure applied to the pressure roller 44 at the center of the fixing roller 42 is lower than the pressure applied to the pressure roller 44 at both ends of the fixing roller 42. As a result, the peripheral speed near both ends of the fixing roller 42 in the fixing nip becomes faster than that near the center. In this embodiment, since the fixing roller 42 transports the paper P in the fixing nip, the peripheral speed near both ends of the fixing roller 42 in the fixing nip becomes faster than the vicinity of the center. As shown in FIG. 5B, the paper is prevented from being wrinkled.

  6A is a cross-sectional view taken along line AA in FIG. 4 when the fixing roller 42 is bent, and FIG. 6B is a cross-sectional view taken along line BB in FIG. 4 when the fixing roller 42 is bent. FIG.

  When the fixing roller 42 is bent, the pressure applied to the pressed roller 44 at the center of the fixing roller 42 also decreases the pressure applied to the pressed roller 44 at both ends of the fixing roller 42. FIG. ) And (b), the nip width and the nip pressure are different between the center portion and the end portion in the width direction of the fixing nip. That is, since the nip width is narrower at the center than at the end, sufficient heating time cannot be obtained, and the fixing performance at the center is lower than at the end. In particular, in the case of thick paper or the like, if the fixing roller is bent as described above, there is a possibility that a fixing failure may occur in the center portion.

  For this reason, if the amount of bending of the fixing roller 42 is reduced so that fixing failure does not occur even with thick paper, the margin of occurrence of wrinkles decreases. As a result, in the case of paper that tends to cause paper wrinkles such as thin paper, the probability that paper wrinkles will occur increases.

  Therefore, in the present embodiment, the area sensor 61 detects an out-of-plane deformation shape in the width direction of the sheet at the entrance of the fixing nip, and adjusts the amount of bending of the fixing roller 42 based on the detection result, thereby making the paper The generation of wrinkles can be suppressed over time, and the optimum amount of bending can be achieved according to the paper type. This will be specifically described below.

FIG. 7 is a control flow chart of the deflection amount adjustment.
First, the control unit 63 specifies the paper type for measuring the out-of-plane deformation shape (S1). 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 and type of the paper P set in the paper feed tray, and the input information is stored in the nonvolatile memory 64. Remember.

  The control unit 63 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 50 stored in the nonvolatile memory 64. Next, the control unit 63 projects the line pattern onto the sheet by the pattern projector 62 (S2), conveys the sheet irradiated with the line pattern to the fixing nip, and the area sensor 61 changes the shape of the line pattern. Measure and detect out-of-plane deformation shapes.

  Surface detected when both ends of the paper P in the width direction move inward due to the occurrence of a slight slip in the fixing nip, which causes an inward velocity vector in the fixing nip with respect to the paper transport direction. The amount of external deformation increases. When the speed distribution in the fixing nip is as shown in FIG. 5A, both ends in the width direction of the paper P are gradually conveyed inward, and as a result, the detected out-of-plane deformation shape is Gradually grows. On the other hand, if there is no situation where both ends in the width direction of the paper P are conveyed inward in the fixing nip, the detection timing of the horizontal line in the vicinity of the end of the paper and in the vicinity of the center does not change. The out-of-plane deformation shape is a flat shape.

  When the convex velocity distribution is obtained, the trailing edge of the sheet is lifted, and the trailing edge of the sheet is conveyed to the fixing nip in a state where the floating is generated. When the speed difference between the center and the edge is very small, the trailing edge of the sheet is slightly lifted, so that no wrinkles or the like occur in the fixing nip. However, when the speed difference between the central portion and the end portion increases, the floating of the rear end of the paper also increases, and the probability that the paper will be wrinkled at the fixing nip increases.

  In addition, the non-volatile memory 64 stores the out-of-limit deformation shapes as shown in Table 1 below, and the control unit 63 detects the environment from a thermohygrometer (not shown) and detects the detected environment. And the corresponding out-of-limit deformed shape on the basis of the paper type information. Further, the control unit 63 calculates the maximum deformation amount based on the detected out-of-plane deformation shape, and checks whether or not the calculated maximum deformation amount is below the limit deformation amount (S4). If the amount exceeds the limit deformation amount (YES in S4), there is a possibility that a major problem has occurred in the fixing device, and if the paper type is used, wrinkles will surely occur. For this reason, if the amount exceeds the limit deformation amount, paper wrinkles occur when the paper type is used. Therefore, an alarm is issued by controlling the speaker, and an indication that the fixing device is to be replaced is displayed on the display unit (S10). ).

When the maximum deformation amount is equal to or less than the limit deformation amount (NO in S4), a deflection adjustment amount is calculated based on the detected out-of-plane deformation shape (S6). Specifically, the non-volatile memory 64 stores an optimal out-of-plane deformation shape in the sheet width direction. This optimal out-of-plane deformed shape in the paper width direction is an out-of-plane deformed shape in the concave shape as shown in FIG. 5B, and the speed at both ends is less than the speed at the center. This is the value when several [%] is early. The optimum out-of-plane deformed shape may be provided for each paper type, or the optimum out-of-plane deformed shape corresponding to each paper type and environment may be provided as in Table 1. Based on the detected out-of-plane deformation shape and the optimum velocity distribution stored in the nonvolatile memory 64, the control unit 63 obtains a deflection adjustment amount (a movement amount of the plunger 67a of the pressing force adjustment mechanism 67). As an example, the relationship between the difference value between the detected out-of-plane deformation shape and the optimum speed distribution stored in the nonvolatile memory 64 and the amount of deflection adjustment of the fixing roller 42 is examined in advance through experiments or the like. A table in which the value and the deflection adjustment amount are associated is stored in the nonvolatile memory 64.
Then, a deflection adjustment amount is obtained from the difference value and the table.

  When the deflection adjustment amount is obtained as described above, the pressing force adjustment mechanism 67 is controlled to bend the fixing roller by the obtained adjustment amount (S7). If the adjustment limit (plunger movement limit) is reached during adjustment (YES in S8), it is determined that the fixing roller 42 has reached the end of its life, an alarm is issued, and the fixing device is replaced with the display unit 66. Is displayed.

  Further, in this embodiment, when the limit of adjustment (movement limit of the plunger 67a) is reached, it is determined that the life of the fixing roller 42 has been reached. A little more usable. Therefore, when the limit of adjustment is reached, the life of the fixing device 40 until the limit out-of-plane deformation shape is reached may be predicted, and notification that the fixing device 40 is to be replaced based on the predicted life may be given. Specifically, the detected out-of-plane deformation shape is stored in the nonvolatile memory 64 in time series. When the adjustment limit (plunger movement limit) is reached, the degree of change of the out-of-plane deformation shape is obtained from the time-series out-of-plane deformation shape data stored in the nonvolatile memory 64, and The time (or the number of printed sheets) required to reach the stored out-of-limit out-of-plane deformation shape is extrapolated. Thereby, the time (number of printed sheets) until the fixing device 40 reaches the end of its life is predicted. A threshold is set from the time (or the number of printed sheets) thus obtained, and when the time or the number of printed sheets reaches the threshold, the display unit 66 displays that the fixing device is to be replaced, and an alarm is output from the speaker 65. generate. As a result, the fixing device can be replaced before wrinkles are reliably generated, and a reduction in productivity can be suppressed.

  Further, when the image forming apparatus includes a communication device, a message indicating that the fixing device is to be replaced may be transmitted to the service center when the threshold is reached. The service life of the fixing device may be predicted at a service center instead of the image forming apparatus. In this case, time-series out-of-plane deformation shape data is appropriately transmitted to the service center, and the time until the fixing device reaches the end of its life (number of printed sheets) is obtained at the service center. Further, by storing the detected out-of-plane deformation shape data in the non-volatile memory 64, when failure occurs, by performing failure analysis based on the out-of-plane deformation shape data stored in the non-volatile memory 64, Identify factors and take appropriate measures.

  Further, when the amount of deflection is adjusted, the fixing nip width and nip pressure in the center portion may be reduced, and fixing failure may occur. For this reason, when the deflection amount is adjusted, it is preferable to change the fixing temperature based on the deflection amount. Thereby, it is possible to suppress the fixing failure at the center as much as possible. The amount of change in the fixing temperature varies for each paper type.

FIG. 8 is a configuration diagram of the out-of-sheet deformation shape detecting means.
The sheet P is conveyed in the direction of arrow B through the nip formed by the fixing roller 42 and the pressed roller 44. The pattern projector 62 is arranged at a predetermined angle with respect to the recording surface of the paper P on the nip entering side, and irradiates the pattern LP over the entire width of the paper P near the nip entering side. The area sensor 61 is arranged in a direction substantially perpendicular to the recording surface of the paper P on the pattern LP forming side of the paper P, and images the pattern LP formed on the paper P. When there is no deflection in the paper P, the pattern LP is captured by the area sensor 61 as a straight line. However, when the paper P is deflected, the height of the paper locally changes due to the waviness of the paper, and the pattern projector 62 The pattern LP irradiated obliquely with respect to the recording surface of the paper P can be understood by the area sensor 61 as a distorted curve.

  Since the amount of out-of-plane deformation of the paper increases and exceeds a predetermined value, it is known that wrinkles occur in the vicinity of the paper.By measuring the amount of out-of-plane deformation of the paper, it is determined whether or not wrinkles are generated. Can be predicted. Further, the out-of-plane deformation amount of the paper P can be obtained from the output of the area sensor 61 by examining the relationship between the height of the paper and the position of the pattern LP in advance.

FIG. 9A shows an out-of-plane deformed shape detection result when wrinkles are generated.
In this figure, the out-of-plane deformation amount of the sheet obtained from the shape of the pattern LP photographed by the area sensor 61 in the process of transporting one sheet is described in time series from time t0 to time tn. When the paper transport speed distribution is convex as shown in FIG. 5A, a speed vector is generated in the paper so that both ends in the width direction are transported in the center direction, and the deflection of the paper occurs as the paper is transported. Occurrence and growth. In the present embodiment, the difference Δmax between the maximum height and the minimum height is used as the maximum deformation amount for various determinations.

FIG. 9B shows an out-of-plane deformed shape detection result in a state where wrinkles are not generated.
When the velocity distribution is concave as shown in FIG. 5B, a velocity vector outward in the width direction is generated on the sheet, and the sheet is conveyed without being bent.

  In the image forming apparatus of FIG. 1, there is one paper feed tray 50 and one type of paper is used. However, there are a plurality of paper feed trays 50, and the paper contained in each paper feed tray 50 is stored. If different types are used and there are multiple types of paper used, is it necessary to adjust the deflection by detecting the out-of-plane deformation in the width direction for each paper stored in each paper feed tray 50? Determine whether or not.

  Specifically, the control unit 63 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 and type of the paper P set in the paper feed tray, and the input information is stored in the nonvolatile memory 64. Remember. The control unit 63 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 50 stored in the nonvolatile memory 64. As described above, when the paper type for measuring the out-of-plane deformation shape is specified, the deflection amount corresponding to the paper type stored in the non-volatile memory 64 is read out, the deflection amount is adjusted, and then the line pattern as described above. And measure the out-of-plane deformation shape. When it is determined that the paper stored in the paper feed tray has the life of the fixing device (when the detected out-of-plane deformed shape is lower than the limit speed), the use of the paper feed tray is prohibited. Further, when it is necessary to adjust the deflection of the paper stored in the paper feed tray (when the speed difference between the center portion and the end portion is 0.1 [%] or more), the deflection amount of the fixing roller for the paper, Find the fixing temperature. Then, the deflection amount and the fixing temperature stored in the nonvolatile memory 64 for each paper type are rewritten to the obtained deflection amount and the fixing temperature. At the time of image forming operation, the paper feed tray to be used is specified, the deflection amount and the fixing temperature corresponding to the paper stored in the paper feed tray are read from the nonvolatile memory 64, and the read deflection amount and the fixing temperature are adjusted. Then, an image forming operation is performed.

  Further, the out-of-plane deformation shape detected for each paper type is stored in the non-volatile memory 64 in time series, and the amount of bending corresponding to the paper stored in a certain paper feed tray is adjusted to the limit of adjustment (the plunger 67a In the same way as described above, the time until the out-of-plane deformed shape of the paper reaches the limit out-of-plane deformed shape or printing from the time-series out-of-plane deformed shape data corresponding to this paper Find the number. Based on the time (or the number of printed sheets) obtained in this way, a threshold value that increases the probability of occurrence of wrinkles is set, and when the time or number of printed sheets reaches the threshold value, the paper stored in the paper feed tray is used. In this case, if this sheet is used before the image forming operation is started, a warning is displayed together with an alarm to the effect that there is a high probability that paper wrinkles will occur. In addition, a display prompting replacement of the fixing device 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. Thereby, since the fixing device in which wrinkles are generated is not used, waste of resources can be prevented.

  As described above, the image forming apparatus of the present embodiment is rotationally driven by the drive source, and forms a fixing nip between the fixing roller 42 as a driving member having at least an elastic layer and the fixing roller 42 in contact with the fixing roller 42. The image forming apparatus includes a fixing device including a pressed roller 44 that is a driven member and a heating roller 41 that is a heating unit that heats a recording sheet that passes through the fixing nip. The control unit 63 serving as a control unit controls the deflection amount of the fixing roller based on the out-of-plane deformation shape in the width direction of the sheet detected by the line sensor 61 (hereinafter referred to as detection out-of-plane deformation shape data). As a result, it is possible to suppress the deterioration of the fixing property at the center as much as possible, to suppress paper wrinkles over time, and to adjust the amount of deflection optimally according to the paper type.

  Further, as the bending forming means, there is provided a pressing force adjusting mechanism 67 that presses both ends of the cored bar portion 42a that is the rotation axis of the fixing roller 42 toward the fixing nip side to bend the driving member. As the pressing force adjusting mechanism 67 presses the cored bar portion 42a of the fixing roller 42 toward the fixing nip, the repulsive force of the pressed roller 44 increases. Since both ends of the fixing roller are pressed by the pressing force adjusting mechanism, even if the repulsive force of the pressed roller 44 increases, the repulsive force moves in the direction opposite to the pressing direction of the pressing force adjusting mechanism 67. However, nothing is supported at the center of the fixing roller 42. For this reason, when the repulsive force of the pressure roller 44 increases, the repulsive force of the pressure roller 44 moves the central portion of the fixing roller 42 to the side opposite to the fixing nip, and the fixing roller 42 bends. . The peripheral speed near both ends of the fixing roller 42 in the fixing nip is faster than that near the center. As a result, the out-of-plane deformation shape of the sheet at the fixing nip becomes as shown in FIG. 5B, and the wrinkle of the sheet is suppressed.

  In addition, by pressing both ends of the cored bar portion 42a, which is the rotation axis of the fixing roller 42, toward the fixing nip, the pressing roller adjustment force 67 is adjusted between the fixing roller bending and the pressing roller side of the fixing roller. This can be done and the number of parts can be reduced.

  In addition, a non-volatile memory 64 serving as a storage unit that stores an appropriate out-of-plane deformation shape of the paper is provided, and the amount of deflection is controlled based on the appropriate out-of-plane deformation shape and the detected out-of-plane deformation shape data. The amount of deflection can be adjusted so as to obtain an appropriate out-of-plane deformed shape.

  Further, by controlling the heating roller based on the amount of bending, fixing failure at the center of the sheet can be suppressed as much as possible.

  Further, the non-volatile memory 64 stores a limit out-of-plane deformation shape that causes wrinkles on the paper, and if the detected out-of-plane deformation shape data reaches the limit out-of-limit deformation shape, a notification means ( A notification that the fixing device is to be replaced is notified by a speaker and a display unit). Thus, the fixing device can be replaced at the stage where wrinkles are generated.

  In addition, when the detection out-of-plane deformation shape data reaches the limit out-of-plane deformation shape, the fixing operation is prohibited, so that the fixing device that generates wrinkles is not used, and the waste of resources is suppressed. be able to.

  The detected out-of-plane deformation shape data is stored in the nonvolatile memory 64 in time series, the life of the fixing device is predicted based on the detected out-of-plane deformation shape data stored in time series, and the life of the fixing device is calculated. If it is predicted that the fixing device is close, a notification that the fixing device is to be replaced is given. As a result, it is possible to suppress the occurrence of downtime of the apparatus by replacing the fixing apparatus before wrinkles are generated.

  Further, based on the detected out-of-plane deformation shape data stored in the non-volatile memory 64 in time series, a threshold for increasing the probability of occurrence of paper wrinkles is calculated for each type of paper, and paper exceeding the threshold is used. In such a case, it is notified that the probability of occurrence of wrinkles is high. As a result, an operation such as switching the paper to be used to another one is promoted, and the generation of wrinkles can be suppressed.

  Each embodiment described above is a preferred embodiment of the present invention, and various modifications can be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 40 Fixing device 41 Heating roller 42 Fixing roller 43 Fixing belt 44 Pressurized roller 45 Heater 61 Area sensor 62 Pattern projector 63 Control part 64 Non-volatile memory 65 Speaker 66 Display part 67 Pushing force adjustment mechanism

JP 2005-195856 A JP 2008-224227 A

Claims (9)

A drive member having an elastic layer;
A fixing device comprising at least an elastic layer, a driven member that forms a fixing nip with the driving member in contact with the driving member, and a heating unit that heats the recording paper that passes through the fixing nip.
When the driving member or the driven member is pressed toward the fixing nip, the driving member or the driven member is set so that the distance from the rotation center near the center of the driving member to the fixing nip is longer than both end portions. Bending forming means for bending;
An out-of-plane deformation shape detecting means for detecting an out-of-plane deformation shape over the entire width of the recording paper at the fixing nip entrance;
A fixing device comprising: a control unit that controls a deflection amount of the drive member or the driven member based on a detection result of the out-of-plane deformation shape detection unit.   The fixing device according to claim 1, wherein the bending forming unit presses both ends of a rotation shaft of the driving member toward the fixing nip side to bend the driving member. Comprising storage means for storing an appropriate out-of-plane deformation shape of the recording paper;
The deflection amount is controlled based on an appropriate out-of-plane deformed shape stored in the storage means and an out-of-plane deformed shape detected by the out-of-plane deformed shape detecting means. Fixing device.   The fixing device according to claim 1, wherein the control unit controls the heating unit based on the deflection amount. Toner image forming means for forming a toner image on recording paper;
Fixing means for fixing a toner image of the recording paper;
Storage means for storing information;
In an image forming apparatus comprising an informing means for informing information,
An image forming apparatus using the fixing device according to claim 1 as the fixing unit. The storage means stores a limit out-of-plane deformation shape that causes wrinkles on the recording paper,
The control means determines whether or not the detection result of the out-of-plane deformation shape detection means has reached the limit out-of-plane deformation shape, and if so, the notification means replaces the fixing device. The image forming apparatus according to claim 5, wherein: The storage means stores a limit out-of-plane deformation shape that causes wrinkles on the recording paper,
The control unit determines whether or not a detection result of the out-of-plane deformed shape detecting unit has reached the limit out-of-plane deformed shape, and prohibits a fixing operation if it has reached. Item 7. The image forming apparatus according to Item 5 or 6.   The storage means stores the detection results detected by the out-of-plane deformed shape detection means in time series, and the control means stores the fixing device based on the detection results stored in the storage means in time series. 8. The apparatus according to claim 5, wherein when the life of the fixing device is predicted and the life of the fixing device is predicted to be near, the notification means notifies that the fixing device is to be replaced. Image forming apparatus. The storage means stores the detection results detected by the out-of-plane deformation shape detection means for each type of recording paper in time series,
The control means calculates, based on the detection results stored in the storage means in time series, a threshold value that increases the probability of occurrence of wrinkling of the recording paper for each type of recording paper, and recording paper that exceeds the threshold is used. 9. The image forming apparatus according to claim 5, wherein the notification means notifies that the probability of occurrence of wrinkles is high.

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