JP2006071925A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly and surely detect a sign where wrinkles are generated on a recording material forming images. <P>SOLUTION: An image forming apparatus 100 forms a regular crest invisible image on paper by using an invisible toner. The image forming apparatus determines whether disturbance occurs on regularity by reading the crest invisible image on the paper with a sensor 45 after fixing treatment. When it is determined that there is a disturbance, the image forming apparatus outputs information related to the occurrence of wrinkles on the paper. Thus, the image forming apparatus transmits information related to wrinkle generation to users, before wrinkles giving serious influence on image quality are generated. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for detecting signs of wrinkles occurring on a recording material on which an image is formed.

  An electrophotographic image forming apparatus such as a color printer or a color copying machine forms a toner image on a sheet (recording material) through several steps of exposure, development, transfer, and fixing. A fixing device that performs fixing among these steps includes a pair of roll members arranged so as to face each other across a paper conveyance path, and a region (nip region) where these roll members contact each other is defined as a sheet. When the toner passes, the toner is fixed to the paper by applying heat and pressure to the paper.

  However, it is known that the paper will wrinkle if the paper enters the nip region in a poor posture or if the heat and moisture content distribution in the paper is uneven. When such wrinkles are continuously generated, the toner image formed on the paper is distorted and the image quality is extremely deteriorated. Therefore, the image forming apparatus cannot withstand further use. In such a case, it is necessary for the user to immediately contact a person who specializes in maintenance of the image forming apparatus and request repair or adjustment of the apparatus.

  Thus, several techniques for detecting wrinkles generated on paper have been proposed. As typical examples, there are technologies described in Patent Documents 1 to 3, for example. The technique described in Patent Document 1 focuses on a phenomenon in which when a wrinkle occurs, a part of the sheet is bent and the thickness of the sheet changes. Specifically, the amount of displacement of the pair of transport roll axes is monitored, and when the amount of displacement becomes extremely large, it is determined that wrinkles have occurred. The technique described in Patent Document 2 also pays attention to the fact that the thickness of the sheet changes when wrinkles occur, as in Patent Document 1, and detects the amount of displacement at both ends of the fixing roll shaft with a sensor to generate wrinkles. Is to detect. The technique described in Patent Document 3 pays attention to the fact that the paper surface becomes uneven when wrinkles occur, and the displacement amount of the distance from the conveyance path surface to the paper (that is, the uneven shape of the paper) is detected by a sensor. It is configured to detect wrinkles and detect wrinkles.

JP-A-5-24713 Japanese Patent Laid-Open No. 9-269697 JP-A-9-202519

  The techniques described in Patent Documents 1 to 3 (hereinafter referred to as the prior art) are used when relatively clear wrinkles such as a part of the paper being bent or a paper surface having an irregular shape are generated. Can be detected. However, since the occurrence of such wrinkles is obvious at first glance when viewing the image quality, the user should be able to recognize the presence of wrinkles without relying on the prior art. In short, these conventional techniques immediately warn the user that a wrinkle has occurred, for example, image forming processing of dozens of sheets to hundreds of sheets in a state where the user has overlooked the generation of wrinkles. It only has the effect of preventing waste that would cause a mistake.

  The present inventor considered the mechanism of wrinkle generation.Wrinkles do not occur suddenly, but at first, signs that cannot be perceived by the human eye gradually appear, and then gradually increase with time. The fact that I am generating has been elucidated. If such a sign of wrinkle occurrence can be detected, the image quality should have deteriorated only to the extent that it is hardly visible at that time, so the user should use the image forming device for the time being. Can continue. Then, the repair or adjustment of the apparatus may be requested with a sufficient time margin during the period of use. That is, it can be said that it is more convenient for the user to quickly detect signs of wrinkles and take appropriate measures.

  The present invention has been made in view of such a background, and an object of the present invention is to quickly and more reliably detect an indication that a recording material on which an image is formed is wrinkled.

  In order to solve the above-described problems, the present invention provides an image forming unit that forms a plurality of images of a predetermined shape on an image carrier at regular intervals along the sub-scanning direction, and transfers the images to a recording material. Fixing means for fixing the image on the recording material by heating and pressurizing the recording material in a nip region where a pair of members facing each other across the conveyance path of the material, and the recording material in the sub-scanning direction A reading unit that sequentially reads the plurality of images fixed on the recording material by the fixing unit while being conveyed, and a time interval at which the reading unit reads the plurality of images from the first recording area of the recording material. And the comparison unit that compares the time interval when the reading unit reads a plurality of the images from the second recording area of the recording material and the time interval compared by the comparison unit does not match Provides an image forming apparatus and an information output means for outputting information related to the occurrence of wrinkles in the recording material.

  Before the recording material starts to wrinkle, the recording material extends or shrinks unevenly. Even if it is a slight expansion / contraction, the regularity of the image formed in each area on the recording material is disturbed by the influence. According to the image forming apparatus of the present invention, the comparison unit reads the time interval when the plurality of images are read from the first recording area of the recording material, and reads the plurality of images from the second recording area of the recording material. When the compared time intervals do not match, the information output means outputs information related to the occurrence of wrinkles in the recording material. Therefore, it is possible to convey information related to the occurrence of wrinkles before wrinkles that significantly affect the image quality occur. Further, according to the present invention, it is based on a slight change in regularity of a plurality of images formed on a recording material, but the interval between the plurality of images can be changed slightly due to disturbance such as a change with time of the image forming apparatus. . Therefore, if the time interval to be compared by the comparison means is fixedly determined at the time of product shipment, for example, there is a possibility that the sign of wrinkle generation cannot be accurately detected due to the influence of disturbance. Therefore, in the image forming apparatus according to the present invention, as described above, it is determined whether or not the regularity of the image is maintained by comparing the time intervals when a plurality of images are read from different regions on the recording material. . In this way, it is possible to detect wrinkle signs more accurately without being affected so much by the above disturbance.

The present invention also provides a visible image forming means for forming a visible image on an image carrier and transferring the image to a recording material, and a plurality of invisible images having a predetermined shape at a fixed interval along the sub-scanning direction. By heating and pressurizing the recording material in a nip region where the invisible image forming means for forming the image on the body and transferring the image onto the recording material and the pair of members facing each other across the conveyance path of the recording material contact Fixing means for fixing the visible image or the invisible image on the recording material, and sequentially reading the plurality of invisible images fixed on the recording material by the fixing means while conveying the recording material in the sub-scanning direction. A reading unit; a time interval at which the reading unit reads the plurality of invisible images from the first recording area of the recording material; and a plurality of the invisible images from the second recording area of the recording material. Comparing means for comparing the time interval that has read the image,
There is provided an image forming apparatus including an information output unit that outputs information related to the occurrence of wrinkles in the recording material when the time intervals compared by the comparison unit do not match.

  Before the recording material starts to wrinkle, the recording material extends or shrinks unevenly, and the regularity of the image formed in each region on the recording material is disturbed. According to the image forming apparatus of the present invention, the comparison unit includes the time interval when the plurality of invisible images are read from the first recording area of the recording material, and the plurality of invisible images from the second recording area of the recording material. The read time interval is compared, and if the compared time intervals do not match, the information output means outputs information related to the occurrence of wrinkles in the recording material. Therefore, it is possible to convey information related to the occurrence of wrinkles before wrinkles that significantly affect the image quality occur. Further, the time interval to be compared by the comparison means is not fixedly determined at the time of product shipment, for example, but the time interval at which a plurality of images are read from different areas on the recording material as described above is used. To determine the regularity of the image. In this way, it is possible to detect wrinkle signs more accurately without being significantly affected by disturbances such as changes over time of the image forming apparatus.

  In the present invention, “visible” and “invisible” mean that an image formed on a recording material can be recognized by the human eye based on the presence or absence of color development due to absorption of a specific wavelength in the visible light region. It means whether it is a degree. The “visible image” is an image that can be visually recognized in the visible light region because the visible developer that forms the visible image has color developability due to absorption of a specific wavelength in the visible light region. On the other hand, an “invisible image” is read by a reading unit such as a photodiode or a CCD in a region other than the visible light region (for example, an infrared light region) using light in the infrared light region as a light source. Since the invisible developer that forms the invisible image does not have color developability due to absorption of a specific wavelength in the visible light region, it can hardly be visually recognized in the visible light region. Means an image.

  In a preferred aspect of the present invention, a calculation means is provided for calculating a difference between the time intervals compared by the comparison means, and calculating an expansion / contraction amount of the recording material based on the difference and the conveyance speed of the recording material. The information output means outputs information having contents corresponding to the amount of expansion / contraction calculated by the calculation means. The amount of expansion and contraction of the recording material indicates the degree of signs that wrinkles will occur, so depending on the degree, for example, there is a large possibility that wrinkles will occur, or there is still a time margin before wrinkles occur. It is possible to output information such as

  Further, the invisible image forming unit forms a plurality of line segment images having a first direction component parallel to the conveyance direction of the recording material and a second direction component parallel to a direction orthogonal to the conveyance direction. May be. In this way, depending on the position of one invisible image, the paper appears in the direction perpendicular to the conveyance direction and the expansion and contraction (indication of wrinkles) of the paper that appears in the conveyance direction when viewed from the position where the invisible image is formed. It is possible to detect the expansion and contraction (signs of wrinkles).

  The invisible image forming means may form the invisible image on an image carrier when the power is turned on in the image forming apparatus, and transfer the image to a recording material. In this way, every time the power is turned on, it can be inspected for signs of wrinkles.

  Further, the image forming apparatus includes a counting unit that counts the number of recording materials on which an image is formed, and the invisible image forming unit carries the invisible image every time the number counted by the counting unit reaches a predetermined value. The image may be formed on a body and transferred to a recording material. In this way, every time the number of recording materials on which an image is formed reaches a predetermined value, it is possible to inspect for signs of wrinkles.

  The invisible image forming unit includes a time measuring unit that measures time, and forms the invisible image on the image carrier every time the time measured by the time measuring unit elapses. The image may be transferred to a recording material. In this way, it is possible to inspect for signs of wrinkles at regular time intervals.

  In another preferred embodiment of the present invention, the visible image forming unit and the invisible image forming unit are configured to superimpose and transfer the visible image and the invisible image formed on the image carrier to the same recording material, respectively. May be. In this way, it is not necessary to transfer only the invisible image to the recording material. However, in this aspect, the reading unit needs to accurately read only the invisible image from the visible image and the invisible image that are superimposed and transferred onto the paper. For this reason, an invisible image is an image that can hardly be visually recognized in the visible light region, and in a region other than the visible light region (for example, an infrared light region), for example, light in the visible light region is used as a light source. In this case, it is necessary to obtain an image that cannot be read by reading means such as a photodiode or a CCD (Charge Coupled Device).

  In another preferable aspect of the present invention, the information output means may output a message indicating that wrinkles may occur in the recording material or wrinkles are starting to occur in the recording material. . In this way, the user of the image forming apparatus can easily know that the recording material may be wrinkled or that the recording material is starting to wrinkle, and can immediately take appropriate measures. it can.

Next, an embodiment of the present invention will be described.
First, main terms used to describe the embodiment are defined.
The “main scanning direction” means a direction in which a line extends when a toner image is formed on the image carrier in units of lines in the image forming apparatus, and coincides with the rotation axis direction of the image carrier. The “sub-scanning direction” is the direction in which the surface of the image carrier moves (rotates) and coincides with the paper transport direction. The main scanning direction and the sub scanning direction are orthogonal to each other.
Next, the direction of wrinkles will be defined. “Wrinkles extending in a direction substantially parallel to the sub-scanning direction of the recording material (paper)” refers to wrinkles Wm generated along the sub-scanning direction as shown in the schematic diagram of FIG. The wrinkles Wm in this direction are generated because the paper P expands and contracts in the main scanning direction. FIG. 1 illustrates a state in which the length Dm in the main scanning direction contracts or extends by Δd in the main scanning direction. On the other hand, the “wrinkle extending in a direction substantially parallel to the main scanning direction of the recording material” refers to a wrinkle Wn generated along the main scanning direction as shown in FIG. The wrinkles Wn in such a direction are generated because the paper P expands and contracts in the sub-scanning direction. FIG. 1 shows a state in which the length Dn in the sub-scanning direction contracts or extends by Δd in the sub-scanning direction.

(1) Apparatus Configuration FIG. 2 is a diagram illustrating an overall configuration of the image forming apparatus 100 according to the embodiment. The image forming apparatus 100 is, for example, a color printer, a color copying machine, or a multifunction machine having a plurality of these functions. As shown in FIG. 2, the configuration of the image forming apparatus 100 is roughly divided into an image forming unit 10, an image reading unit 20, and a paper supply unit 30. Further, the image forming apparatus 100 includes a user interface device 50 for the user to perform various operations. The user interface device 50 includes a liquid crystal display that functions as a touch panel, and the user can perform various operations by touching the liquid crystal display.

  The paper supply unit 30 conveys paper to the image forming unit 10 via a paper supply source such as paper trays 31a, 31b, 31c and a manual feed tray 32 and a conveyance path indicated by a dotted line S in the figure. Transport rolls 34a to 34c and a resist roll 34d are provided. More specifically, the sheets P1, P2, and P3 respectively stored in the sheet trays 31a, 31b, and 31c are fed one by one by the sheet feeding rolls 311a, 311b, and 311c provided in the respective sheet trays 31a, 31b, and 31c. It is sent out to the conveyance path S and further conveyed to the image forming unit 10 by the conveyance rolls 34a to 34c and the registration roll 34d. A plurality of sheets of paper P4 are placed on the upper surface of the manual feed tray 32. These sheets P4 are sent one by one to the conveyance path S by the sheet feeding roll 321 and further conveyed to the image forming unit 10 by the conveyance rolls 34a to 34c and the registration roll 34d.

  The image reading unit 20 includes a document feeder 21 and an optical system member 22 composed of a CCD or the like. The image reading unit 20 reads an image of a document placed in order on a platen glass (not shown) by the document feeder 21 by the optical system member 22 and generates image data representing the read image. The image forming apparatus 100 is connected to a network such as a LAN (Local Area Network) via a communication interface (not shown), and image data transmitted from a host device such as a personal computer or a server machine via the LAN. Receive. The image forming unit 10 performs image forming processing based on the image data generated by the image reading unit 20 and the image data received via the communication interface. Further, at the time of image density correction (so-called calibration) or a “wrinkle detection mode” as described later, the image forming apparatus 100 can also perform image forming processing based on image data stored in advance. It is like that.

  Next, the image forming unit 10 includes a photosensitive drum 11, a charging device 12, an exposure device 13, a rotary developing device 14, a cleaning device 15, an intermediate transfer belt 16, a support roll 17, and a primary transfer roll. 18, a secondary transfer roll 19, a counter roll 40, a conveyance belt 41, and a fixing device 42. A photosensitive layer is formed on the outer peripheral surface (drum surface) of the photosensitive drum 11 and functions as an image carrier. The photosensitive drum 11 is rotated in the direction of arrow a in the drawing by a driving mechanism (not shown). The charging device 12 is, for example, a roll-type charging device or a corotron-type charging device, and uniformly charges the surface of the photosensitive drum 11 to a predetermined potential. The exposure device 13 irradiates the uniformly charged photosensitive drum 11 with laser light modulated in accordance with image data to form an electrostatic latent image on the surface of the photosensitive drum 11.

  The rotary developing device 14 includes Y (yellow), M (magenta), C (cyan), and K (black) toners (developers), respectively, and stores the developing devices 14Y, 14M, 14C, and 14K. A developing device 14F for storing invisible toner is provided. The invisible toner used in the present embodiment has an absorptivity in the visible light region (400 nm to 700 nm) and is not recognized by the human eye because the absorptivity in the visible light region (400 nm to 700 nm) is less than a predetermined ratio. Is readable by a sensor having infrared light sensitivity. When the rotary developing device 14 is rotated in the direction of the arrow b in the drawing by a driving mechanism (not shown), the five developing devices 14Y, 14M, 14C, 14K, and 14F are sequentially placed at positions close to the photosensitive drum 11. Moved. Then, each toner accommodated in each developing device 14Y, 14M, 14C, 14K, 14F is electrically transferred to an electrostatic latent image corresponding to each color (including invisible toner), whereby a photoconductor. A toner image is formed on the surface of the drum 11. FIG. 2 shows a state in which the developing device 14 </ b> F that stores invisible toner is located close to the photosensitive drum 11 and an invisible toner image is formed on the surface of the photosensitive drum 11.

  The intermediate transfer belt 16 is an endless belt member, and its inner peripheral surface is stretched by a plurality of support rolls 17 (two in FIG. 2), a primary transfer roll 18 and a secondary transfer roll 19, It is moved around in the direction of arrow c. The primary transfer roll 18 transfers (primary transfer) the toner image formed on the surface of the photosensitive drum 11 to the outer peripheral surface of the intermediate transfer belt 16 while sandwiching the intermediate transfer belt 16 with the photosensitive drum 11. A cleaning blade 15 provided in the vicinity of the photosensitive drum removes toner remaining on the surface of the photosensitive drum 11 after the primary transfer. The secondary transfer roll 19 transfers (secondary transfer) the toner image transferred to the outer peripheral surface of the intermediate transfer belt 16 to a sheet in a nip region formed between the opposing roll 40. The toner remaining on the surface of the intermediate transfer belt 16 after the secondary transfer is removed by the belt cleaner 23.

  The fixing device 42 includes a fixing roll 42 a and a pressure roll 42 b that are opposed to each other with the conveyance path S therebetween. The fixing roll 42a has an elastic body layer such as silicon rubber formed around a metal core such as aluminum, and a PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) tube or the like on the surface of the elastic body layer. It is a roll member in which the release layer which consists of was formed. Inside the metal core, for example, a heat source such as a halogen lamp is provided and heated from the inside of the roll so that the surface temperature of the fixing roll 42a becomes a predetermined temperature. The pressure roll 42b is a roll member in which an elastic body layer is formed around a metal core and a release layer made of a PFA tube is formed. The pressure roll 42b is moved in the direction of the fixing roll 42a by a pressure spring (not shown). It is energized. The fixing device 42 fixes the toner image on the sheet by rapidly heating the sheet onto which the toner image has been secondarily transferred while applying pressure by the fixing roll 42a and the pressure roll 42b. After this fixing process, the paper is discharged to the paper discharge tray 46 by the paper discharge rolls 43a and 43b.

  A guide 44 for forming a paper transport path is provided between the fixing device 42 and the paper discharge rollers 43a and 43b. A hole 44a is formed in a part of the guide provided above the transport path. A sensor 45 having infrared sensitivity is provided above the hole 44a. Although only one sensor 45 is shown in FIG. 2, in reality, the three sensors 45 are arranged in a line along the depth direction of the paper surface (main scanning direction). This sensor 45 is used to detect wrinkle signs appearing on the paper.

  Next, the configuration of the control system of the image forming apparatus 100 will be described with reference to the block diagram of FIG. In FIG. 3, the control unit 110 includes, for example, an MPU (Micro Processor Unit) and various application specific ASICs (Application Specific Integrated Circuits). The control unit 110 controls operations of the image forming unit 10, the image reading unit 20, and the paper supply unit 30 of the image forming apparatus 100 according to a control program stored in the storage unit 120. The image forming unit 10 includes the sensor 45 described above, and the control unit 110 monitors a sign of wrinkle generation based on an output signal from the sensor 45, and if a sign of wrinkle occurrence appears, a message to that effect. Is displayed on the user interface device 50.

(2) Operation Mode of Image Forming Apparatus The operation modes of the image forming apparatus 100 include “normal mode” and “wrinkle detection mode”. Among these operation modes, the “normal mode” is an operation mode for performing a normal image forming process. That is, an electrostatic latent image corresponding to the image data of each color of Y, M, C, and K is formed on the surface of the photosensitive drum 11 by the exposure device 13, and then the Y, M, C, and K are rotated by the rotary developing device 14. Each color toner is electrically transferred to an electrostatic latent image to be visualized. Then, the toner images of the respective colors are secondarily transferred onto the paper so as to overlap with each other via the intermediate transfer belt 16, and further, the toner image is fixed on the paper by the fixing device 42 and discharged onto the paper discharge tray 46.

  On the other hand, the “wrinkle detection mode” is an operation mode for detecting whether or not there is an indication that wrinkles are generated on the paper as described above. The image forming apparatus 100 sets the operation mode to the “wrinkle detection mode” at a predetermined timing, for example, when the power is turned on, every time an image is formed on a predetermined number of sheets, or every time a predetermined time elapses. Transition. In order to perform such a transition operation, the control program stored in the storage unit 120 includes a computer program in which a procedure for measuring time is described, and a counter for counting the number of sheets on which images are formed. Includes computer programs with procedures.

  In the wrinkle detection mode, the exposure device 13 first forms an electrostatic latent image corresponding to the image data stored in advance in the storage unit 120 of the image forming apparatus 100 on the surface of the photosensitive drum 11. This image data is data representing an image regularly arranged on a sheet. Next, the rotary developing device 14 visualizes the invisible toner accommodated in the developing device 14F by electrically transferring it to the electrostatic latent image. This invisible toner image is primarily transferred to the intermediate transfer belt 16 and then secondarily transferred to a sheet conveyed from a sheet supply source. The invisible toner image that has been secondarily transferred is fixed on the paper by the fixing device 42. The image forming apparatus 100 fixes the invisible toner image on the sheet by the fixing device 42, and then reads the invisible toner image on the sheet by the sensor 45. As the paper expands and contracts slightly and begins to show signs of wrinkling, the regularity of the invisible toner image is disturbed thereby. The image forming apparatus 100 can quickly detect a sign of wrinkle generation by detecting the disorder of regularity with the sensor 45.

(3) Invisible Toner Image Next, the invisible toner image formed on the paper will be specifically described.
FIG. 4 is a plan view showing a state where an invisible toner image is formed on the paper. As shown in FIG. 4, invisible toner images pt representing chevron are regularly arranged at a constant distance interval d along the sub-scanning direction m (the conveyance direction of the paper P). An image row extending in the scanning direction m is formed. Further, a plurality (three in FIG. 4) of image rows constituted by such invisible toner images pt are arranged in the main scanning direction n.

  Here, FIG. 5 is an enlarged view showing one invisible toner image pt. The invisible toner image pt is composed of a line segment pt1 and a line segment pt2 extending in different directions. These line segments pt1 and pt2 both have a direction component parallel to the sub-scanning direction m and a direction component parallel to the main scanning direction n. That is, neither of the line segments pt1 and pt2 is parallel to the main scanning direction and the sub-scanning direction. If each of the line segments pt1 and pt2 has the above two direction components, there is a sign of wrinkles extending in a direction substantially parallel to the sub-scanning direction m (that is, expansion and contraction in the main scanning direction of the paper). Even if it appears, the position of the line segments pt1 and pt2 on the paper is shifted, and a wrinkle sign extending in a direction substantially parallel to the main scanning direction n (that is, expansion and contraction in the sub scanning direction of the paper) appears. Even in such a case, the positions of the line segments pt1 and pt2 on the paper are shifted. FIG. 5 illustrates a particularly preferable case, where the line segments pt1 and pt2 are inclined by 45 ° on the right side and the left side with respect to the main scanning direction m, and the line segment pt1 and the line segment pt2 are mutually connected. It is 90 °.

  Next, FIG. 6 is a plan view of the sensor 45. The sensor 45 is composed of four photodiodes D11, D12, D21, and D22. Further, a set of sensors D1 is configured by the photodiode D11 and the photodiode D12, and a set of sensors D2 is configured by the photodiode D21 and the photodiode D22. The photodiodes D12 and D22 arranged on the upstream side in the sub-scanning direction (conveying direction) m output an output signal in the minus direction corresponding to the detection level. On the other hand, the photodiodes D11 and D21 arranged on the downstream side in the sub-scanning direction (conveying direction) m output a plus direction output signal corresponding to the detection level. The photodiodes D11, D12, D21, and D22 are provided symmetrically with respect to the transport direction m so as to be inclined by the same angle of 45 ° as the line segments pt1 and pt2. As described above, the photodiodes D11, D12, D21, and D22 are disposed at an angle of 45 ° similar to that of the line segments pt1 and pt2. Therefore, the positions of the line segments pt1 and pt2 are shifted by the expansion and contraction of the sheet. In this case, the deviation can be detected accurately. Further, as described with reference to FIG. 5 described above, the line segments pt1 and pt2 are inclined by 45 ° with respect to the transport direction m, respectively, so that when the sheet expands and contracts by Δd in the sub-scanning direction m. The amount of deviation of the position of the line segment pt1 and the amount of deviation of the position of the line segment pr2 are both Δd, and the ratio should be 1: 1. Similarly, when the sheet expands / contracts by Δd in the main scanning direction n, the amount of shift of the position of the line segment pt1 and the amount of shift of the position of the line segment pr2 are both Δd, and the ratio is 1: 1. It should be. By analyzing the shift amount of the positions of the line segments pt1 and pt2 using such a relationship, it is possible to specify the position of the region where the wrinkle sign is present.

  Next, FIG. 7 is a plan view when the sheet P on which the invisible toner image is formed passes through the fixing device 42 as viewed from the direction of the arrow x in FIG. For ease of explanation, the guide 44 provided between the fixing device 42 and the paper discharge rolls 43a and 43b is not shown. In FIG. 7, the fixing roll 42 a and the paper discharge roll 43 a rotate in the direction of the arrow e in the figure, whereby the paper P is conveyed in the sub-scanning direction m, and is discharged in the casing 1 of the image forming apparatus 100. The paper is discharged from the opening to the paper discharge tray 46. Further, as the sensor 45, three sensors 45a, 45b, and 45c are provided so as to be aligned along the main scanning direction n so as to correspond to the columns of the invisible toner images. These sensors 45a, 45b, and 45c read the invisible toner images pt constituting the corresponding columns.

  Here, FIG. 8 is a diagram schematically showing a state when a sign that a parallel wrinkle appears in the sub-scanning direction m appears. In FIG. 8, the individual individual invisible toner images are denoted by symbols pt-a, pt-b, pt-c, and pt-d in this order from the top. As shown in FIG. 8, in the region R extending in parallel with the sub-scanning direction m, when a slight shrinkage (shrinkage amount Δd) that is a sign of wrinkles occurs, the region R in the main scanning direction n is viewed from the position where the region R is generated. The invisible toner images pt-c and pt-d existing on the opposite side move by Δd in the main scanning direction n. In FIG. 8, the invisible toner images pt-c and pt-d move to the right from the original positions represented by dotted lines pt-c ′ and pt-d ′ to the positions represented by solid lines so as to approach the region R. It shows that you are doing.

  Here, the dotted line f1 represents the center of the sensing surface of the sensor D1, and the dotted line f2 represents the center of the sensing surface of the sensor D2. The interval between the invisible toner image pt-a and the invisible toner image pt-b on the sensing surface centers f1 and f2 is a fixed distance interval d. However, when the invisible toner images pt-c and pt-d are shifted by Δd in the direction approaching the region R, the interval between the invisible toner image pt-b and the invisible toner image pt-c on the sensing surface center f1 is d + Δd. The interval between the invisible toner image pt-b and the invisible toner image pt-c on the sensing surface center f2 is d−Δd. Accordingly, the time interval from when the sensor D1 reads the invisible toner image pt-a to when the sensor D1 reads the invisible toner image pt-b, and the sensor D1 reads the invisible toner image pt-b and then reads the invisible toner image pt-c. The time interval until is different. Similarly, a time interval from when the sensor D2 reads the invisible toner image pt-a to when the sensor D2 reads the invisible toner image pt-b, and after the sensor D2 reads the invisible toner image pt-b, The time interval until reading is different.

  Next, FIG. 9 is a diagram schematically showing a state when a sign that a parallel wrinkle occurs in the main scanning direction n appears. In FIG. 9, individual invisible toner images that are continuous are denoted by symbols pt-a, pt-b, pt-c, and pt-d in order from the top in the drawing. As shown in FIG. 9, in the region R extending in parallel with the main scanning direction n, when a slight shrinkage (shrinkage amount Δd) that is a sign of wrinkles occurs, the region R in the sub-scanning direction m is viewed from the generation position of the region R. The invisible toner images pt-c and pt-d existing on the opposite direction side move by Δd in the sub-scanning direction m. In FIG. 9, the invisible toner images pt-c and pt-d move upward from the original positions represented by dotted lines pt-c ′ and pt-d ′ to the positions represented by solid lines so as to approach the region R. It shows that you are doing.

  Here, the interval between the invisible toner image pt-a and the invisible toner image pt-b on the sensing surface centers f1 and f2 is a fixed distance interval d. However, when the invisible toner images pt-c and pt-d are shifted by Δd in the direction approaching the region R, the distance between the invisible toner image pt-b and the invisible toner image pt-c on the sensing surface center f1 is d−Δd. It becomes. Similarly, the interval between the invisible toner image pt-b and the invisible toner image pt-c on the sensing surface center f2 is also d−Δd. Accordingly, the time interval from when the sensor D1 reads the invisible toner image pt-a to the time when the invisible toner image pt-b is read and the time when the sensor D1 reads the invisible toner image pt-b and then reads the invisible toner image pt-c. The time interval until is different. Similarly, a time interval from when the sensor D2 reads the invisible toner image pt-a to when the sensor D2 reads the invisible toner image pt-b, and after the sensor D2 reads the invisible toner image pt-b, The time interval until reading is different.

(4) Operation Example FIG. 10 is a diagram illustrating the relationship between the timing at which an invisible toner image enters the detection region of the sensor 45, the level waveform detected by the sensor 45, and the output signal output by the sensor 45. is there. As described above, the photodiodes D12 and D22 on the upstream side in the transport direction output a negative level waveform corresponding to the detection level, and the photodiodes D11 and D21 arranged on the downstream side in the transport direction correspond to the detection level. A positive level waveform is output. Accordingly, when an invisible toner image pt having the same inclination as that of the photodiodes D12 and D22 enters the detection area of the photodiodes D12 and D22, a level waveform in the minus direction appears first. Next, when the invisible toner image pt enters the detection region by the photodiodes D11 and D21, a level waveform in the positive direction appears. A threshold value k is set in advance in the sensor 45, and when the level waveform is less than the threshold value k, the sensor 45 outputs a low (L) level signal to the control unit 110. On the other hand, when the level waveform is greater than or equal to the threshold value k, the sensor 45 outputs a high (H) level signal to the control unit 110.

If the time t between the timing when the output signal rises from the low level to the high level and the next rise timing is always a constant value t ₀ , the control unit 110 has no sign of wrinkle generation. to decide. That is, as long as a plurality of invisible toner images formed at a constant distance interval d are always read at a constant time interval t ₀ , the invisible toner images should have the original regularity. It is not shrunk and there are no signs of wrinkling. Since the time t, which is a measured value, may include an error, even if the time t of the measured value deviates from t ₀ by a very small value Δt ₀ , it may be considered to match t ₀ .

On the other hand, when the time t does not always take a constant value, it means that the position of the invisible toner image pt is shifted as described with reference to FIGS. Judge that there are signs of wrinkling.
Here, when the time t does not always take a constant value, there are the following two patterns.
FIG. 11 is a diagram for explaining the first pattern. In FIG. 11, level waveforms Fa, Fb, and Fc indicate level waveforms detected by the sensors 45a, 45b, and 45c, respectively. Output signals Ga, Gb, and Gc indicate output signals output from the sensors 45a, 45b, and 45c, respectively. As shown in FIG. 10, two level waveforms should be detected by one sensor 45 and two output signals should be output. In FIG. 11, in order to simplify the explanation, Only one of the level waveform and the output signal is shown (the same applies to FIG. 12 described later).

In FIG. 11, for example, focusing on the output signal Ga, only two specific invisible toner images pt are read at the time interval t ₁ , and all other invisible toner images are read at the time interval t _0. It is shown. That is, the time interval (= t ₁ ) for the invisible toner image from one area (first recording area) of the paper and the time interval (= t) for reading the invisible toner image pt from another area (second recording area). ₀ ) does not match. This means that the time t does not always take a constant value, and in this case, the control unit 110 determines that there is a sign of wrinkle occurrence.

Next, focusing on the output signals Ga, Gb, and Gc in FIG. 12, only two specific invisible toner images pt are read at the time interval t ₂ in the output signal Gb, and invisible toner in the output signals Ga and Gc. It is shown that all images are read at time interval t ₀ . Also in this case, the time interval (= t ₂ ) for the invisible toner image from a certain area (first recording area) of the paper and the time interval (for reading the invisible toner image pt from another area (second recording area)) = T ₀ ) does not match. Therefore, the control unit 110 can determine that there is a sign of wrinkle occurrence.

  In this way, when the control unit 110 determines that there is a sign of the occurrence of wrinkles, the control unit 110 displays a message to that effect on the user interface device 50. In this case, based on the principle described with reference to FIGS. 8 and 9, the control unit 110 may have a sign that wrinkles extending in a direction substantially parallel to the main scanning direction may occur, or may be substantially the same as the sub scanning direction. It may be determined whether there is an indication that wrinkles extending in a parallel direction occur, and information corresponding to the determination result may be output. For example, if there is an indication that wrinkles are generated along the main scanning direction, the control unit 110 causes the user interface device 50 to display a message to that effect, while there is an indication that wrinkles are generated along the sub scanning direction. If there is, a message indicating that is displayed on the user interface device 50.

Further, the degree of the sign of wrinkle generation based on a certain time interval t ₀ and the time interval (time interval t ₁ , t ₂ described above) and the time difference when reading cannot be performed at the time interval t _0. Can also be predicted. Specifically, if Δd is obtained by multiplying the time difference between the time intervals t ₁ , t ₂ and the time interval t ₀ by the sheet conveyance speed, the Δd substantially corresponds to the expansion / contraction amount of the sheet (region R). Will do. Since the amount of expansion / contraction indicates the degree of signs that wrinkles are generated, the control unit 110 indicates that, for example, the possibility that wrinkles are generated is large, or the time until the wrinkles are generated is temporal. Various information such as a sufficient margin may be displayed on the user interface device 50. Note that the paper P after the invisible toner image is read may be discharged to the paper discharge tray 46 as it is.

As described above, before the wrinkle starts to occur on the paper, the paper extends or shrinks unevenly, and the regularity of the invisible toner image formed on the paper is disturbed. The image forming apparatus 100 according to the present embodiment determines whether or not the regularity is disturbed, and outputs information related to the occurrence of wrinkles on the sheet when it is determined that there is a disorder. Therefore, before wrinkles that significantly affect the image quality occur, information related to the occurrence of wrinkles can be transmitted to the user.
The above-described embodiment is based on a slight change in regularity of the plurality of invisible toner images pt formed on the paper. The distance between the plurality of invisible toner images pt is, for example, the time of the image forming apparatus 100. It can change slightly due to disturbances such as changes. Therefore, if the time interval t0 to be compared is fixedly determined at the time of product shipment, for example, there is a possibility that the sign of wrinkle generation cannot be accurately detected due to the influence of disturbance. Therefore, in the image forming apparatus 100 according to the above-described embodiment, the regularity of the invisible toner image pt is maintained by comparing the time intervals at which the plurality of invisible toner images pt are read from different recording areas of the paper as described above. Judge whether or not. In this way, it is possible to more accurately detect the wrinkle sign without being affected by the disturbance as described above.

(5) Modifications The embodiment described above can be modified as follows.
In the embodiment, a so-called cycle system and an image forming apparatus including the photosensitive drum 11 as the image carrier and the rotary developing device 14 have been described as examples. A so-called tandem type image forming apparatus in which the drum is arranged in series along the outer periphery of the intermediate transfer belt may be used. Further, the image forming apparatus 100 is not limited to the one that forms a color image using Y, M, C, and K toners (developers), and uses a developer of colors such as red, blue, and green. It may be one that forms a monochrome image.

  Here, FIG. 13 is a diagram showing a configuration of the image forming apparatus 101 when the present invention is applied to a tandem image forming apparatus. In FIG. 13, image forming engines 1Y, 1M, 1C, and 1K respectively form yellow (Y), magenta (M), cyan (C), and black (K) toner images. Further, the image forming engine 1F forms an invisible toner image using invisible toner. For example, the image forming engine 1Y includes a photoconductor 11 drum Y rotating in the direction of arrow A, a charging device 12Y that uniformly charges the photoconductor drum 11Y to a predetermined charging potential, and Y, M, C, and K colors. An exposure device 13Y for forming an electrostatic latent image by irradiating the photosensitive drum 11Y with light corresponding to Y (yellow) image data of the image data, and supplying yellow toner to the electrostatic latent image to provide the photosensitive drum A developing device 14Y for forming a toner image on the surface of 11Y, a primary transfer roll 15Y for primary transfer of the toner image to the intermediate transfer belt 2, and a toner remaining on the surface of the photosensitive drum 11Y after the primary transfer are removed. And a cleaning device 16Y. In addition, the image forming engine 1F responds to image data indicating a photosensitive drum 11F, a charging device 12F that charges the photosensitive drum 11F to a predetermined charging potential, and an invisible toner image stored in advance by the image forming device 101. An exposure device 13F that forms an electrostatic latent image by irradiating the photoreceptor 11F with the light, a developing device 14F that supplies an invisible toner to the electrostatic latent image and forms an invisible toner image on the surface of the photoconductor 11F, and an intermediate A primary transfer roll 15F for primary transfer of an invisible toner image to the transfer belt 2 and a cleaning device 16F for removing toner remaining on the surface of the photoreceptor 11F after the primary transfer are provided. Other configurations of the image forming engines 1M, 1C, and 1K are substantially the same as those of the image forming engines 1K and 1F except that the types of toner are different.

  The intermediate transfer belt 2 is stretched around a plurality of various rolls 3, and is rotated around these rolls 3 in the arrow B direction. The toner images formed by the image forming engines 1Y, 1M, 1C, and 1K are primarily transferred onto the intermediate transfer belt 2 that is moved in this manner so as to overlap. Further, the invisible toner image formed by the image forming engine 1F is primarily transferred to the intermediate transfer belt 2.

  A plurality of sheets are stored in the sheet tray 4, and the sheet sent to the conveyance path by the sheet feeding tray 4 a is conveyed in the direction of arrow C by the plurality of conveyance rolls 5. The secondary transfer roll 6 secondarily transfers the toner image primarily transferred to the intermediate transfer belt 2 as described above onto a sheet conveyed on the conveyance path. The fixing device 7 fixes the toner image secondarily transferred on the sheet to the sheet by heating and pressing. A guide 9 is formed between the fixing device 7 and the paper discharge roll 8 to form a paper conveyance path. A hole 9a is formed in a part of the guide provided above the conveyance path. A sensor 9b having infrared sensitivity is provided above the hole 9a. Although only one sensor 9b is shown in FIG. 13, in reality, the three sensors 9b are arranged in a line in the depth direction of the drawing. The sensor 9b reads an invisible toner image on the paper and outputs an output signal as shown in FIGS. 10 to 12 according to the read result. Based on the output signal from the sensor 9b, the control unit of the image forming apparatus 101 monitors for signs of wrinkles. If a wrinkle sign appears, a message to that effect is displayed on the upper surface of the casing of the image forming apparatus 101. Is displayed on the user interface device 50 provided in. The above is the embodiment when the present invention is applied to a tandem image forming apparatus.

  The shape and arrangement pattern of the invisible toner image are not limited to those illustrated in FIG. The shape may be any predetermined shape, and the arrangement pattern is arbitrary.

  In the embodiment, in the wrinkle detection mode different from the normal image formation mode, only the invisible toner image is formed on the sheet to monitor the sign of wrinkle generation. However, the present invention is not limited to this. For example, an invisible toner image may be superimposed on an image formed in the normal image forming mode. If an appropriate material for the invisible toner image is selected, even if the image is a mixture of a visible image and an invisible image, as described in, for example, Japanese Patent Application Laid-Open No. 2003-186238, the sensor Can accurately read only the invisible image without being disturbed by the visible image. If the image for detecting the wrinkle sign is invisible, there is no need for the user to know the presence of the invisible image, or the paper on which the invisible image is formed can be used again. There are benefits. However, when it is not necessary to receive these merits, the image for detecting the wrinkle sign is not necessarily invisible, but is a visible image using visible toners such as Y, M, C, and K. May be.

  The sensor 45 is not limited to a photodiode, and may be any sensor that can read an image. For example, a CCD may be used.

  In addition, the fixing device 42 is not limited to one constituted by two roll members. In short, the fixing device 42 is formed by heating and pressurizing the sheet in a nip region where a pair of members facing each other across the sheet conveyance path is in contact. Any configuration that fixes a toner image on a sheet may be used. For example, a fixing device in which a belt member is sandwiched between a fixing roll and a pressure roll and the pressure roll is biased toward the fixing roll to form a nip region may be used. Alternatively, a fixing device may be provided in which a pad or roll is provided inside the tube member, and the pad or roll is urged toward the fixing roll through the tube to form a nip region.

  In the embodiment, the paper is described as an example of the recording material on which the toner image is formed. However, various recording materials such as a plastic such as an OHP film and a cloth can be used. .

  The control program executed by the control unit 110 described in the embodiment includes a magnetic tape, a magnetic disk, a floppy (registered trademark) disk, an optical recording medium, a magneto-optical recording medium, a CD (Compact Disk) -ROM, a DVD ( Digital Versatile Disk) and a recording medium such as a RAM can be provided.

It is a schematic diagram explaining the direction of the wrinkle which generate | occur | produces in embodiment of this invention. 1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. 2 is a block diagram illustrating a configuration of a control system of the image forming apparatus. FIG. 3 is a plan view showing an invisible toner image formed on a sheet by the image forming apparatus. FIG. It is a figure which shows an invisible toner image. It is a figure which shows the structure of a sensor. FIG. 6 is a plan view showing a state in which a paper on which an invisible toner image is formed passes through a fixing device and a paper discharge roll. It is the figure which showed typically a mode when the sign of a wrinkle parallel to the subscanning direction m generate | occur | produced. It is the figure which showed typically a mode when the sign of a wrinkle parallel to the main scanning direction n generate | occur | produced. It is the figure which illustrated the relationship between the timing which an invisible toner image approaches the detection area | region of a sensor, the waveform of the detection signal detected by a sensor, and the waveform of the output signal output by a sensor. It is the figure which illustrated the relationship between the waveform of the detection signal detected by a sensor, and the waveform of the output signal output by a sensor. It is the figure which illustrated the relationship between the waveform of the detection signal detected by a sensor, and the waveform of the output signal output by a sensor. It is a figure which shows the structure of the image forming apparatus which concerns on the modification of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Image forming apparatus, 10 ... Image forming unit, 11 ... Photosensitive drum, 12 ... Charging device, 13 ... Exposure apparatus, 14 ... Rotary developing device, 14Y, 14M, 14C, 14K, 14F ... developer, 16 ... intermediate transfer belt, 18 ... primary transfer roll, 19 ... secondary transfer roll, 20 ... image reading unit, 30 ... paper supply Units 31a, 31b, 31c... Paper tray, 42... Fixing device, 43... Discharge roll, 44... Guide, 45 (45a, 45b, 45c). User interface device 110, control unit 120, recording unit, pt, invisible toner image, D11, D12, D21, D22, photodiode.

Claims (3)

Image forming means for forming a plurality of images of a predetermined shape on the image carrier at regular intervals along the sub-scanning direction, and transferring the images to a recording material;
Fixing means for fixing the image to the recording material by heating and pressurizing the recording material in a nip region where a pair of members opposed across the conveyance path of the recording material contact;
Reading means for sequentially reading the plurality of images fixed on the recording material by the fixing means while conveying the recording material in the sub-scanning direction;
A time interval when the reading unit reads the plurality of images from the first recording area of the recording material, and a time interval when the reading unit reads the plurality of images from the second recording area of the recording material. A comparison means for comparing;
An image forming apparatus comprising: an information output unit that outputs information related to the occurrence of wrinkles in the recording material when the time intervals compared by the comparison unit do not match. A visible image forming means for forming a visible image on an image carrier and transferring the image to a recording material;
Invisible image forming means for forming a plurality of invisible images of a predetermined shape on the image carrier at regular intervals along the sub-scanning direction, and transferring the images to a recording material;
Fixing means for fixing the visible image or the invisible image to the recording material by heating and pressurizing the recording material in a nip region where a pair of members opposed across the conveyance path of the recording material contact;
A reading unit that sequentially reads the plurality of invisible images fixed on the recording material by the fixing unit while conveying the recording material in the sub-scanning direction;
The time interval when the reading unit reads the plurality of invisible images from the first recording area of the recording material, and the time interval when the reading unit reads the plurality of invisible images from the second recording area of the recording material. A comparison means for comparing
An image forming apparatus comprising: an information output unit that outputs information related to the occurrence of wrinkles in the recording material when the time intervals compared by the comparison unit do not match. Obtaining a difference between the time intervals compared by the comparison means, and based on the difference and the conveyance speed of the recording material, calculating means for calculating the expansion / contraction amount of the recording material,
The image forming apparatus according to claim 1, wherein the information output unit outputs information of contents corresponding to the amount of expansion / contraction calculated by the calculation unit.

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