JP2006089206A - Image forming device and recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To rapidly reliably detect a symptom of generation of wrinkles in a recording material with an image formed thereon. <P>SOLUTION: Regularly arrayed invisible images are formed in advance on a wrinkle detection paper sheet. In an image forming device 100, visible images are formed on the wrinkle detection paper sheet and fixed, invisible images on the paper sheet are read by a sensor 45 to determine whether or not the regularity is disturbed. If it is determined that the regularity is disturbed, information related to generation of the wrinkles on the paper sheet is output. Thus, information related to generation of wrinkles can be transmitted to a user before wrinkles seriously affecting the 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. Typical examples thereof include techniques 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 inventor considered the mechanism of wrinkle generation. It has been elucidated that mystery occurs. 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. It is possible to continue to do this, and it is possible to request repair or adjustment of the apparatus with sufficient time 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 problems, the present invention provides an image forming means for forming a visible image on an image carrier and transferring the image to a recording material, and a pair of members facing each other across the conveyance path of the recording material. A fixing unit that fixes the visible image on the recording material by heating and pressurizing the recording material in a nip region, a reading unit that reads an invisible image from the recording material that has undergone a fixing process by the fixing unit, and the reading Determining means for determining whether or not the invisible images read by the means are regularly arranged; and when the determining means determines that the images are not regularly arranged, An image forming apparatus including an information output unit that outputs information related to the occurrence of wrinkles is provided.

  Before the recording material starts to wrinkle, the recording material extends or shrinks unevenly. Even if it is a slight expansion / contraction, it affects the image formed on the recording material and its regularity is disturbed. According to the image forming apparatus of the present invention, the determination unit determines whether or not the images read by the reading unit are regularly arranged, and when it is determined that the images are not regularly arranged. 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.

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, the “invisible image” is a reading means such as a photodiode or a CCD (Charge Coupled Device) in a region other than the visible light region (for example, an infrared light region) when light in the infrared light region is used 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 is almost visually recognized in the visible light region. Means an image that cannot be done.
In particular, according to the present invention, since the visible image and the invisible image are superimposed on the recording material, it is necessary to accurately read only the invisible image from the visible image and the invisible image. 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 such a case, it is desirable to form an image that cannot be read by reading means such as a photodiode or CCD.

  In a preferred aspect of the present invention, the determination unit determines that the invisible images are regularly arranged when the reading unit reads the plurality of invisible images at a constant time interval. If the plurality of invisible images are not read by the reading unit at regular time intervals, it is determined that the invisible images are not regularly arranged. In this way, the determination unit can determine whether or not the invisible image has regularity based on whether or not the plurality of invisible images have been read by the reading unit at regular time intervals. That is, the regularity of an invisible image can be determined with a relatively simple configuration.

  In another preferable aspect of the present invention, the image forming unit includes a plurality of storage units that store the recording material, and the image forming unit displays the formed visible image when the image forming process is performed only after the power is turned on. The image is transferred to a recording material supplied from a specific storage unit among the plurality of storage units, and the reading unit reads the invisible image from the recording material supplied from the specific storage unit and subjected to a fixing process. In this way, every time the power is turned on, it can be inspected for signs of wrinkles.

  In another preferable aspect of the present invention, the image forming unit includes a plurality of storage units that store the recording material, and a counting unit that counts the number of recording materials on which an image is formed. The formed visible image is transferred to a recording material supplied from a specific storage unit among the plurality of storage units each time the number of sheets counted by the number reaches a predetermined value, and the reading unit is configured to transfer the specific storage unit. The invisible image is read from the recording material supplied from the means and subjected to the fixing process. 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.

  In another preferable aspect of the present invention, the recording apparatus includes a plurality of storage units that store the recording material and a time measuring unit that measures time, and the invisible image forming unit determines the time measured by the time measuring unit. The formed visible image is transferred to a recording material supplied from a specific storage unit among the plurality of storage units, and the reading unit is supplied from the specific storage unit. The invisible image is read from the recording material that has undergone the fixing process.

  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.

  In addition, the present invention provides a recording material in which invisible images are regularly arranged in a certain direction, and a plurality of image rows formed of the invisible images are arranged so as to be orthogonal to each other. The present invention also provides a recording material in which a plurality of invisible images are arranged at a certain distance interval in a certain direction and a plurality of invisible images are arranged at a certain distance interval in a direction orthogonal to the certain direction. .

First, main terms used to describe the embodiment of the present invention 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. “Wrinkle extending in a direction substantially parallel to the sub-scanning direction of the recording material (paper)” refers to a wrinkle Wm generated along the sub-scanning direction m 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 n. 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 n 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.

Hereinafter, embodiments of the present invention will be described in detail.
(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 sheet supply unit 30 includes a sheet supply source and a conveyance unit for conveying the sheet from the sheet supply source to the image forming unit 10 via a conveyance path indicated by a dotted line S in the drawing. The paper supply source includes a plurality of means for storing paper such as paper trays 31a, 31b, 31c and a manual feed tray 32. Further, the transport means includes transport rolls 34a to 34c and a resist roll 34d. A specific transport operation is as follows. The sheets P1, P2, and P3 respectively accommodated in the sheet trays 31a, 31b, and 31c are sent to the conveyance path S one by one by the sheet feeding rolls 311a, 311b, and 311c provided in the sheet trays 31a, 31b, and 31c. . These sheets are further transported to the image forming unit 10 by transport rolls 34a to 34c and a resist 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.

  Among the paper trays 31a, 31b, 31c and the manual feed tray 32, a specific pattern (in this embodiment, the paper tray 31a) is a sheet on which a regular pattern image is previously formed with invisible toner as described later. Is housed. Since this sheet is used to detect signs of wrinkles, it is hereinafter referred to as “wrinkle detection sheet” in order to distinguish it from a sheet (normal sheet) used for the purpose of normal image formation.

  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.

  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 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 developing units 14Y, 14M, 14C, and 14K that respectively store toners (developers) of respective colors of Y (yellow), M (magenta), C (cyan), and K (black). Yes. 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 four developing devices 14Y, 14M, 14C, and 14K are sequentially moved to positions close to the photosensitive drum 11. It is done. Then, each toner accommodated in each developing unit 14Y, 14M, 14C, 14K is electrically transferred to an electrostatic latent image corresponding to each color, whereby a toner image is formed on the surface of the photosensitive drum 11. It is formed.

  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 conveyance path, and a sensor 45 having infrared light sensitivity is provided above the hole 44a. In FIG. 2, only one sensor 45 is shown, but in reality, three sensors 45 are arranged in a line in the depth direction of the drawing. The sensor 45 is used to detect a wrinkle sign appearing on the paper (wrinkle detection 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), and performs image formation according to a control program stored in the storage unit 120. The operations of the image forming unit 10, the image reading unit 20, and the paper supply unit 30 of the apparatus 100 are controlled. 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. Is displayed on the user interface device 50.

(2) Operation Mode of Image Forming Apparatus Image forming processing modes of the image forming apparatus 100 include a “normal mode” and a “wrinkle detection mode”. Among these operation modes, the “normal mode” is an operation mode in which normal image forming processing is performed, and sheets (normal sheets) stored in the sheet trays 31 b and 31 c and the manual feed tray 32 are used. 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 changes the operation mode at a predetermined timing, for example, when an image is formed for the first time after 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 to “wrinkle detection mode”. In order to perform such a transition operation, the control program stored in the storage unit 120 includes a computer program for detecting power-on, a computer program in which a procedure for measuring time is described, and an image. A computer program in which a procedure for counting the number of sheets formed is described is included. In the wrinkle detection mode, the image forming process itself is performed in the same procedure as in the normal mode described above. The difference from the “normal mode” is that the paper used in the “wrinkle detection mode” is a “wrinkle detection paper” stored in a specific paper tray 31a, and the sensor 45 is activated to detect the “wrinkle detection paper”. The invisible toner image is read from the image and an attempt is made to detect whether or not a wrinkle sign has appeared. Note that it is sufficient to use one to several wrinkle detection sheets to detect the occurrence of wrinkles. Therefore, the control unit 110 forms an image using a predetermined number of wrinkle detection sheets in the wrinkle detection mode. After performing the processing, the normal mode may be changed again.

(3) Invisible Toner Image Next, the invisible toner image formed on the wrinkle detection paper will be specifically described.
FIG. 4 is a plan view showing the configuration of an invisible toner image on the wrinkle detection sheet. As shown in FIG. 4, a plurality of image rows lm1, lm2, lm3, ln1, ln2, and ln3 are formed on the surface of the wrinkle detection sheet P. Each of these image rows lm1, lm2, lm3, ln1, ln2, and ln3 is configured by regularly arranging a plurality of chevron invisible toner images pt at a constant interval d. The image rows lm1, lm2, and lm3 extend in a direction parallel to the side N of the wrinkle detection paper P. When the wrinkle detection paper P is conveyed in a direction parallel to the side N (Y direction in the drawing), the wrinkles are detected. Used to detect signs of occurrence. The image rows ln1, ln2, and ln3 extend in a direction parallel to another side M of the wrinkle detection paper P, and the wrinkle detection paper P is conveyed in a direction parallel to the side M (X direction in the drawing). Sometimes used to detect signs of wrinkling.

  Generally, when a sheet is stored in a sheet tray or a manual feed tray, it is left to the user to determine whether the sheet is stored vertically or horizontally. When the wrinkle detection sheet P is stored, for example, sideways, the sheet is conveyed in a direction parallel to the side N (the Y direction in the figure), so the X direction in FIG. The direction is the sub-scanning direction. On the other hand, when the wrinkle detection paper P is stored vertically, the paper is conveyed in a direction parallel to the side M (X direction in the figure), so the X direction becomes the sub-scanning direction and the Y direction becomes It becomes the main scanning direction. Regardless of the direction in which the wrinkle detection sheet P is conveyed, the image sequence used to detect the occurrence of wrinkles is an image sequence extending in a direction parallel to the sub-scanning direction.

  Further, the invisible toner used in the present embodiment has an absorptivity in the visible light region (400 nm to 700 nm) that is less than a predetermined ratio and cannot be recognized by the human eye, and in the near infrared light region (800 nm to 1000 nm). Since the absorption rate is equal to or higher than a predetermined ratio, it can be read by a sensor having infrared light sensitivity. In particular, in the present embodiment, an arbitrary visible image desired by the user is superimposed on the invisible toner image pt previously formed on the wrinkle detection paper P. Therefore, for example, as described in Japanese Patent Application Laid-Open No. 2003-186238, even if the image is a mixture of a visible image and an invisible image by selecting an appropriate material for the invisible toner image, The sensor 45 can accurately read only the invisible toner image pt without being disturbed by the visible image.

  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. Each of these line segments pt1 and pt2 has a direction component parallel to the sub-scanning direction m of the wrinkle detection sheet and a direction component parallel to the main scanning direction n. When the wrinkle detection sheet slightly expands and contracts and signs of wrinkles begin to occur, the regularity of the invisible toner image is disturbed thereby, and the image forming apparatus 100 detects the disorder of the regularity with the sensor 45. As a result, it is possible to quickly detect signs of wrinkles. If each of the line segments pt1 and pt2 has the two direction components as described above, even if the wrinkle detection sheet expands and contracts in the direction parallel to the sub-scanning direction m, the main scanning direction Even when the wrinkle detection sheet is expanded or contracted, it is easy to detect that the positions of the line segments pt1 and pt2 on the wrinkle detection sheet are shifted due to the expansion and contraction. FIG. 5 illustrates a particularly preferable case. The line segments pt1 and pt2 are inclined by 45 ° with respect to the sub-scanning direction m, and the line segment pt1 and the line segment pt2 are mutually 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, and one set of sensors D1 is composed of the photodiode D11 and the photodiode D12, and one pair of sensors is composed of the photodiode D21 and the photodiode D22. A sensor D2 is configured. The photodiodes D12 and D22 arranged on the upstream side in the sub scanning direction m output an output signal in the minus direction corresponding to the detection level, and the photodiodes D11 and D21 arranged on the downstream side in the sub scanning direction m are A plus direction output signal corresponding to the detection level is output. The photodiodes D11, D12, D21, and D22 are provided symmetrically with respect to the sub-scanning direction m so that the photodiodes D11, D12, D21, and D22 are inclined at an angle of 45 ° similar to 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. When it deviates, 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 sub-scanning direction m, so that there is a wrinkle detection sheet in a direction parallel to the sub-scanning direction m. When the line segment pt1 (or line segment pr2) is displaced by a certain amount Δd, and when the wrinkle detection sheet expands / contracts by a certain amount Δd in the main scanning direction n, the line segment pt1 (line segment) The amount of displacement of the position of pt2) should have a 1: 1 relationship. By analyzing the shift amount of the positions of the line segments pt1 and pt2 using such a relationship, it is also possible to specify the position where the wrinkle sign appears (the position where the paper has expanded and contracted).

  Next, FIG. 7 is a plan view of the state when the wrinkle detection sheet P on which the invisible toner image pt 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. Further, an arbitrary visible image desired by the user should be formed on the wrinkle detection sheet P that has undergone the fixing process, but the illustration thereof is omitted in FIG. In FIG. 7, the sheet P is conveyed in the sub-scanning direction (the direction of the arrow m) by rotating the fixing roll 42 a and the paper discharge roll 43 a in the direction of arrow e in the figure, and is provided in the casing 1 of the image forming apparatus 100. The paper is discharged from the discharged paper outlet 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 image row of the invisible toner image. Each of these sensors 45a, 45b, and 45c reads invisible toner images pt constituting image rows extending in the sub-scanning direction (in the case of FIG. 7, image rows lm1, lm2, and lm3), and inspects the regularity thereof.

(4) Operation Example FIG. 8 is a diagram illustrating the relationship between the timing at which the invisible toner image pt enters the detection area of the sensor 45, the level waveform detected by the sensor 45, and the output signal output by the sensor 45. is there.
The photodiodes D12 and D22 arranged on the upstream side in the sub-scanning direction m output a negative level waveform corresponding to the detection level, and the photodiodes D11 and D21 arranged on the downstream side in the sub-scanning direction m are A level waveform in the positive direction according to the detection level is output. Accordingly, when the invisible toner image pt enters the detection region by the photodiodes D12 and D22, first, a negative level waveform appears, and then when the invisible toner image pt enters the detection region by the photodiodes D11 and D22, the positive direction. Level waveform appears. A threshold value k is set in advance in the sensor 45. 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. 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 a predetermined value t ₀ , the control unit 110 determines that there is no sign of wrinkle generation. To do. That is, when the invisible toner image pt that should have been formed at a constant distance interval d is read at a constant time interval t ₀ , the invisible toner image maintains regularity, so that the wrinkle detection sheet extends. It is not shrunk and there are no signs of wrinkling. Note that t ₀ can be obtained by calculation in advance based on the conveyance speed of the wrinkle detection sheet and the distance interval d of the invisible toner image, so that it may be stored in the storage unit 120 in advance. Further, since the measurement value t may include an error, even if the measurement value t deviates from t ₀ by a certain minute value Δt ₀ , it may be considered that it matches t ₀ .

On the other hand, as shown in FIG. 9, when the time t is not the predetermined value t ₀ but t ₁ or t ₂ , it means that the position of the invisible toner image on the wrinkle detection sheet is shifted. Therefore, the control unit 110 determines that there is a sign of wrinkle occurrence. That is, when the invisible toner image pt that should have been formed at the constant distance interval d cannot be read at the constant time interval t ₀ , the invisible toner image pt has no regularity. The wrinkle detection paper is expanding and contracting, and there are signs of wrinkle generation. In this case, the control unit 110 outputs information related to the occurrence of wrinkles on the paper. For example, the user interface device 50 is displayed with a message indicating that there is a possibility that the paper is wrinkled or that the paper is starting to wrinkle.

  Note that for the region where the image sequences lm1, lm2, lm3 and the image sequences ln1, ln2, ln3 shown in FIG. 4 overlap, the sensor 45 is not limited to the image sequences lm1, lm2, lm3 extending in the sub-scanning direction. The image sequences ln1, ln2, ln3 extending in the scanning direction are also read. However, since the expansion and contraction phenomenon that appears on the wrinkle detection sheet P before the occurrence of wrinkles is a phenomenon at a very small level, the displacement amount of the position of the invisible toner image pt is also very small. For this reason, the output value peaks in the image sequences lm1, lm2, and lm3 even when the sensor 45 reads the unnecessary image sequences ln1, ln2, and ln3 in addition to the originally intended image sequences lm1, lm2, and lm3. The appearing time interval is almost constant with a slight deviation. On the other hand, the time difference between the peak of the output value in the image sequence lm1, lm2, lm3 and the peak of the output value in the image sequence ln1, ln2, ln3 is the time interval at which the peak of the output value appears in the image sequence lm1, lm2, lm3. It is expected to be larger than the slight deviation. Focusing on this point, the control unit 110 can analyze the level waveform detected by the sensor 45 and extract a waveform corresponding only to the image sequences lm1, lm2, and lm3. In this case, it is desirable to determine the position of each invisible toner image pt so that the reading results of the image rows lm1, lm2, lm3 and the reading results of the image rows ln1, ln2, ln3 can be easily separated. That is, it is desirable that the invisible toner images constituting each image row are not so close to each other in the region where the image rows lm1, lm2, lm3 and the image rows ln1, ln2, ln3 overlap.

  As described above, before the wrinkle starts to be generated on the paper, the paper extends or shrinks unevenly, and the regularity of the invisible toner image formed on the wrinkle detection 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.

  In the embodiment, a wrinkle detection sheet for detecting the occurrence of wrinkles is stored only in a specific tray among a plurality of trays. When a predetermined timing arrives, the wrinkle detection paper is supplied from the specific tray to perform the image forming process, and at the same time, the wrinkle detection paper is consumed wastefully to try to detect signs of wrinkle generation. There is nothing. Further, on the wrinkle detection paper, an image row extending in a direction parallel to one side of the paper and an image row extending in a direction parallel to another side are formed vertically and horizontally. Therefore, it is possible to detect the sign of wrinkle generation regardless of the orientation of the wrinkle detection sheet in the tray and the conveyance direction.

(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. 10 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. 10, image forming engines 1Y, 1M, 1C, and 1K respectively form toner images of yellow (Y), magenta (M), cyan (C), and black (K) colors. 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. Other configurations of the image forming engines 1M, 1C, and 1K are the same as those of the image forming engine 1Y 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. In addition, an 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 trays 4 a and 4 b, and the sheets sent out to the conveyance path by the sheet feed rolls 41 a and 41 b are conveyed in the direction of arrow C by the plurality of conveyance rolls 5.
Note that normal paper is stored in the paper tray 4a, and wrinkle detection paper is stored in the paper tray 4b. 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. In FIG. 10, only one sensor 9b is shown, but actually 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 wrinkle detection sheet and outputs output signals as shown in FIGS. 8 to 9 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.

  Further, the shape and arrangement pattern of the invisible toner image are not limited to those illustrated in FIG. 4, and any shape or arrangement pattern can be adopted as long as it has a certain regularity. In particular, as shown in FIG. 4, if it is important to avoid confusion between the read results of both image sequences for the region where the image sequences lm1, lm2, lm3 and the image sequences ln1, ln2, ln3 overlap, You can do as follows. For example, FIG. 11 shows an example in which the invisible toner image pt is not formed at all in the region where the image rows lm1, lm2, lm3 and the image rows ln1, ln2, ln3 overlap. In FIG. 12, the recording surface of the wrinkle detection sheet is divided into two regions, and image sequences lm1, lm2, and lm3 are formed in one region, and image sequences ln1, ln2, and the like are formed in the other region. In this example, ln3 is formed. FIG. 13 is an example in which image rows are formed by changing the direction of the invisible toner image pt (the direction of the convex shape of the chevron) between the image rows lm1, lm2, and lm3 and the image rows ln1, ln2, and ln3. . As described above, the directions of the photodiodes D11, D12, D21, and D22 of the sensor 45 are inclined by 45 ° toward the sub-scanning direction, and the directions of the line segments pt1 and pt2 constituting the invisible toner image pt are also sub-scanning. Inclined by 45 ° toward the direction. Therefore, even if the image sequence is formed as shown in FIG. 13, the sensor 45 can read the image sequence lm1, lm2, lm3 or the image sequence ln1, ln2, ln3 with sufficient accuracy. is there. However, since the appearance of the level waveform detected by the sensor 45 is different between the image sequences lm1, lm2, and lm3 and the image sequences ln1, ln2, and ln3, the control unit 110 detects the orientation of the wrinkle detection sheet and detects the orientation thereof. It is necessary to change the level waveform analysis method according to the situation.

  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. FIG. 6 is a plan view showing an invisible toner image formed on a wrinkle detection sheet. It is an enlarged view showing an invisible toner image. It is a figure which shows the structure of a sensor. FIG. 6 is a plan view illustrating a state in which a wrinkle detection sheet passes through a fixing device and a sheet discharge roll. 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 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 a figure which shows the structure of the image forming apparatus which concerns on the modification of this invention. It is a top view which shows the invisible toner image currently formed in the wrinkle detection paper in the modification of this invention. It is a top view which shows the invisible toner image currently formed in the wrinkle detection paper in the modification of this invention. It is a top view which shows the invisible toner image currently formed in the wrinkle detection paper in 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 ... developer, 16 ... intermediate transfer belt, 18 ... primary transfer roll, 19 ... secondary transfer roll, 20 ... image reading unit, 30 ... paper supply unit, 31a, 31b, 31c ... paper tray, 42 ... fixing device, 43 ... paper discharge roll, 44 ... guide, 45 (45a, 45b, 45c) ... sensor, 50 ... user Interface device, 110... Control unit, 120... Recording unit, pt... Invisible toner image, pt 1, pt 2 ... line segment, D 11, D 12, D 21, D 22.

Claims (7)

An image forming means for forming a visible image on an image carrier and transferring the image to a recording material;
Fixing means for fixing the visible 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 reads an invisible image from a recording material that has undergone a fixing process by the fixing unit;
Determining means for determining whether or not the invisible images read by the reading means are regularly arranged;
An image forming apparatus comprising: an information output unit that outputs information related to the occurrence of wrinkles in the recording material when the determination unit determines that the images are not regularly arranged. The determination means includes
When a plurality of the invisible images are read by the reading unit at regular time intervals, it is determined that the invisible images are regularly arranged;
The image forming apparatus according to claim 1, wherein when the plurality of invisible images are not read at a predetermined time interval by the reading unit, it is determined that the invisible images are not regularly arranged. A plurality of storage means for storing the recording material;
When the image forming unit performs an image forming process for the first time after power is turned on, the formed visible image is transferred to a recording material supplied from a specific storage unit among the plurality of storage units,
The image forming apparatus according to claim 1, wherein the reading unit reads the invisible image from a recording material supplied from the specific storage unit and subjected to a fixing process. A plurality of storage means for storing the recording material;
Counting means for counting the number of recording materials on which an image is formed,
The image forming unit transfers the formed visible image to a recording material supplied from a specific storage unit among the plurality of storage units each time the number of sheets counted by the counting unit reaches a predetermined value.
The image forming apparatus according to claim 1, wherein the reading unit reads the invisible image from a recording material supplied from the specific storage unit and subjected to a fixing process. A plurality of storage means for storing the recording material;
And a time measuring means for measuring time,
The invisible image forming unit applies the formed visible image to a recording material supplied from a specific storage unit among the plurality of storage units each time the time measured by the time measuring unit elapses. Transcript,
The image forming apparatus according to claim 1, wherein the reading unit reads the invisible image from a recording material supplied from the specific storage unit and subjected to a fixing process.   A recording material in which invisible images are regularly arranged in a certain direction, and a plurality of image rows formed of the invisible images are arranged so as to be orthogonal to each other.   A recording material in which a plurality of invisible images are arranged at a certain distance interval in a certain direction, and a plurality of invisible images are arranged at a certain distance interval in a direction orthogonal to the certain direction.

Images