JP5056311B2 - Image forming apparatus - Google Patents

Description

  The present invention forms an electrostatic latent image by performing exposure according to an image signal, develops the formed electrostatic latent image, and transfers and fixes it onto the conveyed paper. The present invention relates to an image forming apparatus for forming an image.

  2. Description of the Related Art Conventionally, image forming apparatuses such as printers and copiers have been widely used, and technologies relating to various elements constituting such image forming apparatuses have also been widely used. Among image forming apparatuses, an image forming apparatus that employs an electrophotographic system has an image holding body such as a photoconductor, and the charged image holding body is irradiated with light so that the potential of the surrounding electric potential is By forming different electrostatic latent images on the image carrier, a pattern to be printed is often formed, and an exposure unit for forming an electrostatic latent image by irradiating light onto the image carrier is provided. ing. The electrostatic latent image formed by the exposure unit is developed with a developer containing toner, and is finally transferred and fixed on a sheet to form an image. At this time, since the density of the image transferred onto the paper is determined by the amount of light irradiated by the exposure unit, the role played by the exposure unit is important in realizing an image with a desired density. It has become.

  In an electrophotographic image forming apparatus, the exposure unit includes a large number of light emitting diodes (LEDs), and an electrostatic latent image is formed by irradiating an image carrier with light from these light emitting diodes (LEDs) There is one with LPH (LED Print Head) that forms The LPH is an exposure unit in which a plurality of components constituting the exposure unit are set, such as a light emitting unit that generates light for irradiation and a light collecting unit that collects light from the light emitting unit on an image carrier. By simply incorporating the LPH into the image forming apparatus, the plurality of components can be collectively provided in the image forming apparatus. Therefore, maintenance and the like are easy, and there are many image forming apparatuses that employ LPH.

  In LPH, there may be a light emitting diode that does not emit light normally and does not emit light normally due to a failure of the light emitting diode or a driving unit that drives the light emitting diode. When image formation is performed in a state where a light emitting failure of the light emitting diode has occurred, streaky density unevenness occurs in the image due to insufficient irradiation of the light emitting diode of the light emitting failure. Even if there are some light emitting diodes with poor light emission, if these light emitting diodes with poor light emission are scattered, the density unevenness due to the light emitting failure of the light emitting diodes remains as a minor image quality defect that is difficult for humans to recognize. Therefore, the light emitting failure of the light emitting diode is not a problem. However, when light emitting diodes with poor light emission are concentrated in one place, density unevenness that can be clearly recognized by the human eye appears in the image, and degradation of image quality becomes a serious problem.

  As a measure for avoiding the output of an image whose image quality has deteriorated, a measure can be simply considered that when the presence of a light emitting diode adjacent to a defective light emission is detected, the image formation is stopped and the engineer who performs repair waits for arrival. However, this measure inevitably reduces the productivity of image formation by stopping the image formation until an engineer who repairs arrives.

Recently, an LPH (see, for example, Patent Document 1) in which a movable slit is provided between a light emitting unit and a light condensing unit has been proposed. The position of the slit is changed so that the light around the light emitting diode with poor light emission, which is partially reduced, does not pass through the slit, and the above-described problem of image quality defects is avoided. For this reason, it is possible to continue image formation and maintain productivity of image formation.
JP 2000-343746 A

  However, in the method of Patent Document 1, it is necessary to obtain a sufficient amount of light for forming an electrostatic latent image only with light that passes through the slit, and does not pass through the slit. Therefore, if the amount of light that is wasted without contributing to the formation of the electrostatic latent image is included, the total amount of light emission required for forming the electrostatic latent image is much higher than that of a normal LPH that does not have such a slit. It will be big. For this reason, the cost of image formation is high, and the method of Patent Document 1 is not appropriate for realizing an image forming apparatus suitable for cost reduction.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an image forming apparatus that suppresses a decrease in image formation productivity due to the presence of a light emission failure and is also suitable for cost reduction.

In order to achieve the above object, an image forming apparatus of the present invention comprises:
A paper transport unit for transporting paper,
An exposure unit that includes a plurality of light emitting elements arranged in the width direction intersecting the paper conveyance direction, and forms an electrostatic latent image by performing exposure according to an image signal;
A developed image forming unit for developing the electrostatic latent image formed by the exposure unit to form a developed image;
An image forming unit that forms an image on the paper by transferring and fixing the developed image formed by the developed image forming unit onto the conveyed paper;
A detection unit for detecting that a light emission failure has occurred in the exposure unit;
When the occurrence of a light emission failure is detected by the detection unit, the exposure unit is exposed to an image signal representing a sample image for image quality defect detection to form an electrostatic latent image, and the development image formation And a control unit for forming a developed image of the electrostatic latent image on the part and forming the sample image on a sheet in the image forming part.

  The image forming apparatus according to the present invention forms a sample image on a sheet when the occurrence of a light emission failure is detected, so that the user can detect an image quality defect associated with the occurrence of the light emission failure at any position on the paper due to the light emission failure. You can know if it appears. For this reason, the user can take measures to prevent image quality defects from appearing in the image, such as changing to a smaller paper size or reducing the image, and can continue to form the image desired by the user. Can be prevented from decreasing. In addition, this method is an extremely simple method in which a sample image is formed on a sheet when the occurrence of a light emission failure is detected, and thus is suitable for cost reduction.

  In the image forming apparatus of the present invention, “a plurality of sets of the exposure unit, the developed image forming unit, and the detection unit are provided, and the control unit emits light of the plurality of sets. A development image representing the sample image is formed in a group to which an exposure unit in which occurrence of a defect is detected belongs, and a plurality of types of paper sizes are included in the group to which the exposure unit in which occurrence of a light emission failure is not detected. A developed image representing a frame image having a frame representing the size of the image is formed, and further, the developed image representing the sample image and the developed image representing the frame image are superimposed on the image forming unit and transferred and fixed onto the paper. The form “is made to perform” is a preferred form.

  According to such a form, the user can know which paper size is used so that an image quality defect does not appear in an image without using a measuring instrument such as a ruler.

  In the image forming apparatus of the present invention, “a plurality of sets of the exposure unit, the developed image forming unit, and the detection unit are provided, and the control unit emits light of the plurality of sets. A developed image representing the sample image is formed in a group to which an exposure unit in which the occurrence of a defect is detected belongs, and a scale arranged at a predetermined interval in the group to which the exposure unit in which the occurrence of a light emission failure is not detected among the plurality of groups. A developed image representing a scale image having a color image is formed, and further, the developed image representing the sample image and the developed image representing the scale image are superimposed on the image forming unit and transferred and fixed on a sheet. An image reading unit that reads an image recorded on a sheet and generates an image signal; and the image reading unit reads and generates an image on the sheet on which the sample image and the scale image are superimposed. Is based on the image signal, the form of and a position specifying unit for specifying a quality defect position on the paper where the image quality defect has occurred "is also preferable.

  According to such a form, the user can grasp the image quality defect position only by causing the image reading unit to read the image in which the sample image and the scale image are superimposed.

  In the image forming apparatus of the present invention, “a plurality of sets of the exposure unit, the developed image forming unit, and the detection unit are provided, and the control unit emits light of the plurality of sets. A developed image representing a two-dimensional code for detecting an image quality defect position is formed as the sample image in the group to which the exposure unit in which the occurrence of a defect is detected belongs, and the developed image is transferred / fixed onto the paper in the image forming unit. An image reading unit that reads an image recorded on a sheet and generates an image signal; and the two-dimensional code generated by reading the two-dimensional code on the sheet by the image reading unit. It is also a preferable mode that the image processing apparatus includes a position specifying unit that specifies an image quality defect position on the paper on which the image quality defect has occurred based on the image signal to be expressed.

  According to such a form, the user can grasp the image quality defect position only by causing the image reading unit to read the two-dimensional code.

  Further, in the image forming apparatus of the present invention including the image reading unit, “based on the image quality defect position specified by the position specifying unit, the size of the paper on which the image forming unit performs image transfer / fixing is determined. The form of “having a size restricting section that restricts the size of the paper to avoid the occurrence of occurrence” is a more preferable form.

  According to such a form, the image reading unit is limited to the size of the paper and has an image quality defect only by reading the image in which the sample image and the scale image are superimposed or reading the two-dimensional code. The output of the image is avoided, which is convenient.

  Further, in the image forming apparatus of the present invention including the image reading unit, “the control unit is arranged in the width direction so as to avoid the occurrence of the image quality defect based on the image quality defect position specified by the position specifying unit. An embodiment in which the electrostatic latent image is shifted and transferred onto a sheet whose position is relatively adjusted in the width direction is also a more preferable embodiment.

  According to such a form, it is possible to avoid the output of an image with a defective image quality simply by causing the image reading unit to read the image in which the sample image and the scale image are superimposed or to read the two-dimensional code. It is convenient.

  According to the present invention, it is possible to suppress a decrease in image formation productivity due to the presence of a light emission failure, and it is also suitable for cost reduction.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 1 is an overall configuration diagram of an image forming apparatus according to the present exemplary embodiment.

  The image forming apparatus of this embodiment is a color printer for duplex output.

  The image forming apparatus 1000 includes electrophotographic laminated image carriers 61K, 61C, 61M, and 61Y that rotate in the directions of arrows Bk, Bc, Bm, and By in the drawing. It has been. Further, around each image carrier, roll-shaped charging members 65K, 65C, 65M, 65Y, which are in contact with each image carrier and charge each image carrier while being rotated by the rotation of each image carrier. By irradiating the light obtained by the light emission of the LED onto each charged image carrier, the potential of each color of black (K), cyan (C), magenta (M), and yellow (Y) LPH (LED Print Head) 7K, 7C, 7M, and 7Y that form an electrostatic latent image different from the potential of the toner, and electrostatically attaching each color toner to electrostatic latent image on each image carrier. Developing devices 64K, 64C, 64M, and 64Y are provided for developing and forming developed images. Here, the LPHs 7K, 7C, 7M, and 7Y correspond to an example of the exposure unit in the present invention. The four developing devices 64K, 64C, 64M, and 64Y are respectively replenished with toner of each color component from the four toner cartridges 4K, 4C, 4M, and 4Y by a mechanism (not shown). Further, the image forming apparatus 1000 includes an intermediate transfer belt 5 that receives a transfer (primary transfer) of each color development image formed on each image carrier and conveys a primary transfer image, and each image carrier. Cleaning devices 63K, 63C, 63M, and 63Y that remove toner remaining on the intermediate transfer belt, and primary transfer rolls 50K, 50C, 50M, and 50Y that perform primary transfer of the developed images of the respective colors onto the intermediate transfer belt 5. A secondary transfer roll pair 9 for performing secondary transfer of the primary transfer image on the transfer belt 5 to the paper, a fixing device 10 for fixing the unfixed secondary transfer image transferred on the paper to the paper, and LPH are provided. First, a controller 4 that controls each unit in the image forming apparatus 1000, three trays 1a, 1b, and 1c that store three types of paper having different paper sizes, designation of paper sizes, and enlargement / reduction of images Such as rate of specified operating panel 91 for receiving the operation by the user for setting the image forming conditions, the display screen 90 for displaying the settings and operation contents of the image forming apparatus 1000 is also provided. Here, the intermediate transfer belt 5 circulates and moves in the direction of arrow A in the figure while being stretched between the first secondary transfer roll 9b and the drive roll 5a while receiving a driving force from the drive roll 5a. The intermediate transfer belt 5 is pressed against the second secondary transfer roll 9a by the first secondary transfer roll 9b, and the above-described secondary transfer roll pair 9 is connected to the first secondary transfer roll 9b. The second secondary transfer roll 9a.

  An image signal representing an image is input to the controller 4 from the outside of the image forming apparatus 1000. The controller 4 processes the image signal and sends it to the LPH of each color as an image signal for the four colors described above. An electrostatic latent image is formed.

  Next, an image forming operation in the image forming apparatus 1000 will be described.

  The four image carriers 61K, 61C, 61M, and 61Y are charged by the charging members 65K, 65C, 65M, and 65Y, respectively, and receive the ED light emitted from the LPHs 7K, 7C, 7M, and 7Y and receive the image carriers. An electrostatic latent image is formed thereon. The formed electrostatic latent image is developed with each developer containing toner of each color by the developing devices 64K, 64C, 64M, and 64Y to form a developed image of each color. The developed images of the respective colors formed in this way are yellow (Y), magenta (M), cyan (C) on the intermediate transfer belt 5 in the primary transfer rolls 50K, 50C, 50M, and 50Y corresponding to the respective colors. ) And black (K) are sequentially transferred (primary transfer) and superposed to form a multicolor primary transfer image. The multicolor primary transfer image is conveyed to the secondary transfer roll pair 9 by the intermediate transfer belt 5. On the other hand, out of the three trays 1a, 1b, and 1c, the paper in the tray for storing the paper of the paper size designated in advance by the user is taken out in response to the formation of the multi-color primary transfer image. The paper is transported by some of the first transport roll pair 3 a, the first transport roll pair 3 b, and the third transport roll pair 3 c, and the paper is prepared by the registration roll pair 8. Then, the multi-color primary transfer image is transferred (secondary transfer) to the conveyed paper by the secondary transfer roll pair 9, and further fixed to the secondary transfer image on the paper by the fixing device 10. Is given. In FIG. 1, the paper conveyance path at this time is shown as a path indicated by an upward dotted arrow.

  When image formation is performed only on one side of the sheet, the sheet passes through the sheet conveyance path only once, and after the secondary transfer image is fixed in the fixing device 10, as indicated by a dotted arrow in the right direction in the figure. In addition, the paper passes through the fourth transport roll pair 13 and the delivery roll pair 8a and is discharged to the paper discharge tray 2 as it is.

  When image formation is performed on both sides of a sheet, the secondary transfer image is transferred and fixed on one side of the sheet by passing through a sheet conveyance path indicated by an upward arrow, and is not discharged to the sheet discharge tray 2. It goes back and passes between the first double-sided conveyance roll pair 8b and is conveyed downward through a path indicated by a downward dotted arrow. Then, after passing between the second double-sided conveyance roll pair 8 c, the third double-sided conveyance roll pair 8 d turns upward and goes again to the secondary transfer roll pair 9. Here, during the period from when the sheet is first transferred by the secondary transfer roll pair 9 to when the sheet reaches the position of the secondary transfer roll pair 9 again, a new multi-layer is formed on the intermediate transfer belt 5 by the method described above. A primary transfer image of color is formed. Then, when the sheet reaches the secondary transfer roll pair 9 for the second time, the new multicolor primary transfer image is transferred to the surface on the side opposite to that when the sheet is subjected to the second transfer for the first time. Next transferred. Then, a fixing process is performed on the new secondary transfer image on the opposite surface by the fixing device 10, and the sheet on which the fixed image is formed on both sides is discharged to the discharge tray 2.

  Here, in both the case of image formation on both sides of the paper and the case of image formation on one side of the paper, the image is secondarily transferred onto the paper in such a manner that the long direction of the paper is along the paper conveyance path described above. Is done.

  The above is the description of the image forming operation in the image forming apparatus 1000.

  Next, the LPHs 7K, 7C, 7M, and 7Y provided in the image forming apparatus 1000 will be described. These four LPHs all have the same configuration, and here, the LPHs for these colors will be collectively described as LPH7. The four image carriers 61K, 61C, 61M, and 61Y have the same configuration. In the following description of LPH7, the image carriers 61K, 61C, 61M, and 61Y for each color in FIG. The image holding member 61 will be described. Therefore, the description will be made assuming that the LPH 7 irradiates the image holding member 61 with light.

  FIG. 2 is a diagram showing a schematic configuration of LPH 7 provided in image forming apparatus 1000 shown in FIG.

  The LPH 7 includes a light emitting unit 72 configured by a predetermined number of LED groups 720 each including a predetermined number of light emitting diodes (LEDs) 721 and a large number of cylindrical Selfoc lenses 710. A condensing unit 71 is provided that condenses the received light on the image holding member 61 using the SELFOC lens 710. In each LED group 720, the LEDs 721 are arranged along the extending direction of the image carrier 61 (the direction of the rotation axis of the image carrier 61) as shown in the figure. The adjacent LED groups 720 are arranged in a zigzag manner while the relative positions of the adjacent LED groups 720 in the direction perpendicular to the rotation axis of the image carrier 61 (the depth direction in the figure) are slightly shifted. Therefore, the LED 721 in the light collecting unit 71 is arranged in the direction of the rotation axis of the image holding member 61 as a whole of the light collecting unit 71, and this arrangement direction is a direction perpendicular to the paper conveyance direction in FIG. (The direction perpendicular to FIG. 1), which corresponds to the short direction of the conveyed paper.

  In the formation of the electrostatic latent image described above, the LED 721 in an appropriate position for forming the electrostatic latent image among these LEDs 721 in accordance with the image signal sent from the controller 4 in FIG. Light is emitted by driving a drive unit (not shown) to form an electrostatic latent image on the image holding member 61.

  In general, in the LPH, there may be a light emitting diode that does not emit light normally and does not emit light normally due to a failure of a light emitting diode or a driving unit that drives the light emitting diode. When image formation is performed in a state where a light emitting failure of the light emitting diode has occurred, streaky density unevenness extending in the paper transport direction is generated in the image due to insufficient irradiation of the light emitting diode of the light emitting failure. Even if there are some light emitting diodes with poor light emission, if these light emitting diodes with poor light emission are scattered, the density unevenness due to the light emitting failure of the light emitting diodes remains as a minor image quality defect that is difficult for humans to recognize. Therefore, the light emitting failure of the light emitting diode is not a problem. However, when light emitting diodes with poor light emission are concentrated in one place, density unevenness that can be clearly recognized by the human eye appears in the image, and degradation of image quality becomes a serious problem.

  In the image forming apparatus 1000 in FIG. 1, when three or more LEDs 721 arranged in a row are defective in light emission, the image quality defect detection pattern for detecting the image quality defect is displayed as the three trays 1a and 1b in FIG. , 1c, the paper is output on the paper of the maximum paper size among the papers of the three paper sizes stored. As a result, by observing the output image quality defect detection pattern, the user can know which paper size of the paper can be used to obtain an image free from image quality defects. Hereinafter, the output of the image quality defect detection pattern by the image forming apparatus 1000 will be described in detail.

  FIG. 3 is a flowchart showing an operation flow when the image forming apparatus 1000 in FIG. 1 outputs an image quality defect detection pattern.

  When the image output instruction is received by the user (step S1; Yes), prior to the output of the image, the image forming apparatus 1000 is provided in the LED 7, and a light emitting failure is detected using a detection circuit not shown in FIG. The presence or absence of the LED 721 is detected (step S2).

  FIG. 4 is a schematic diagram showing a detection circuit 722 that detects the presence or absence of an LED 721 with a defective light emission, and FIG. 5 is a diagram showing signals input to and output from this detection circuit when detecting the LED 721 with a defective light emission. .

  One detection circuit 722 for detecting the presence or absence of the defective LED 721 is provided for each of the LED groups 720 shown in FIG. 2, and this detection circuit 722 allows the presence or absence of the defective LED 721 of the LEDs 721 in the LED group 720. Is detected. The detection circuit 722 includes two amplifiers, an input signal amplifier 7223 and an output signal amplifier 7224. In the input signal amplifier 7223, an input signal and an amplifier are respectively supplied from a first terminal 7223a and a second terminal 7223b. The control signal is input, and the output signal amplifier 7224 outputs an output signal from the output terminal 7224a. As shown in FIG. 4, an output side terminal (not shown) of the input signal amplifier 7223 is wired to an input side terminal (not shown) of the output signal amplifier 7224, and whether or not there is a light emission failure. The LED output terminal 721 c of the LED 721 to be detected is also wired via the first resistor 7221. The output-side terminal of the input signal amplifier 7223 and the input-side terminal of the output signal amplifier 7224 are grounded via a second resistor 7222 having a very large resistance value.

In the LED 721, the LED input terminal 721a is wired to a power source (not shown), and when the power is on, the potential of the LED input terminal 721a is V _DD that is the value of the power source voltage. The LED 721 is also provided with an LED control signal terminal 721b to which an LED control signal is input and an LED output terminal 721c that is an output side terminal of the LED 721. If the LED 721 is normal (that is, defective in light emission). Otherwise, the current flows through the LED 721 when the potential of the LED input terminal 721a is higher than the potential of the LED output terminal 721c and the potential of the LED control signal terminal 721b is equal to or higher than a predetermined potential. LED 721 emits light. Except for this state, almost no current flows through the LED 721 and the LED 721 does not emit light. The light emission control of the LED 721 when forming the latent image is performed by setting the potential of the LED control signal terminal 721b by inputting the LED control signal while maintaining the potential of the LED input terminal 721a higher than the potential of the LED output terminal 721c. Done by controlling. On the other hand, when detecting the presence or absence of a light emission failure, the potential of the LED input terminal 721a is maintained at V _DD which is the value of the power supply voltage, and the potential of the LED control signal terminal 721b is maintained above the predetermined potential. The

When detecting the presence or absence of light emission failure, as shown in FIG. 5, as the input signal and the amplifier control signal of the input signal amplifier 7223, the potential is V _DD which is the value of the power supply voltage or a step of 0 (zero), respectively. The function signal is input. At this time, in the input signal amplifier 7223, when the potential of the first terminal 7223a is 0 and the potential of the second terminal 7223b is V _DD , the impedance of the input signal amplifier 7223 becomes extremely large, A state in which no current flows through the input signal amplifier 7223 is realized. Hereinafter, the flow of detection of the presence or absence of a light emission failure will be described in detail with reference to the time variation of the signal waveform in FIG.

As described above, the detection of the presence or absence of light emission failure is performed in a state where the potential of the LED input terminal 721a is maintained at V _DD and the potential of the LED control signal terminal 721b is maintained at the predetermined potential or higher. Initially, in the input signal amplifier 7223, the potential of the first terminal 7223a to which the input signal is input is maintained at V _DD, and the potential of the second terminal 7223b to which the amplifier control signal is input is maintained at 0. In this state, first, in the input signal amplifier 7223, the potential of the first terminal 7223a is changed from V _DD to 0 as shown in region A of FIG. Next, as illustrated in region B of FIG. 5, the potential of the second terminal 7223b is changed from 0 to V _DD . As described below, whether or not there is a light emission failure is determined by a change in the potential of the output terminal 7224a when the potential of the first terminal 7223a becomes 0 and the potential of the second terminal 7223b becomes V _DD . Since the response of the input signal amplifier 7223 to the change in the potential of the first terminal 7223a is not very good, as described above, there is a time difference between the change in the potential of the first terminal 7223a and the change in the potential of the second terminal 7223b. Is provided.

In a section in which the potential of the first terminal 7223a and the potential of the second terminal 7223b are both 0, the terminal on the output side (not shown) of the input signal amplifier 7223 is also at potential 0, and if the LED 721 is normal (that is, light emission). Almost all of the current flowing through the LED 721 flows into the input signal amplifier 7223 and no current flows through the output signal amplifier 7224 (if not defective). At this time, the potential of the output terminal 7224a from which the output signal is output is the same potential 0 as the ground potential. Here, as shown in region B of FIG. 5, when the potential of the second terminal 7223b is changed from 0 to V _DD , as described above, the impedance of the input signal amplifier 7223 becomes extremely large, and this time, The current does not flow through the input signal amplifier 7223. As a result, almost all of the current flowing through the LED 721 flows into the output signal amplifier 7224, and the potential of the output terminal 7224a from which the output signal is output changes as shown in a region C in FIG.

On the other hand, if the LED 721 is defective in light emission, no current flows through the LED 721. Therefore, even if the potential of the second terminal 7223b to which the amplifier control signal is input is changed from 0 to V _DD , The potential does not change, and the second terminal 7223b is maintained at the same potential as the potential before the potential is changed from 0 to V _DD (the same potential 0 as the ground potential).

The output signal from the output terminal 7224a is input to the controller 4 in FIG. 1, and the controller 4 is as described above when the potential of the second terminal 7223b to which the amplifier control signal is input is changed from 0 to V _DD. Whether or not there is a change in the potential of the output terminal 7224a is determined. The determination of whether or not the LED 721 has a light emission failure is performed for all the LED groups 720 in the LPH 7 in the direction of the rotation axis of the image carrier 61 in each LED group 720 (a direction perpendicular to the paper conveyance direction in FIG. 1). ) Are performed in the order of arrangement.

  Note that various conventional techniques such as the disconnection detection technique described in Japanese Patent Application Laid-Open No. 2002-280190 can be employed to determine whether or not the LED 721 has a light emission failure.

  In the above description, the four LPHs 7Y, 7M, 7C, and 7K in FIG. 1 are representatively described to determine whether or not the LED 721 has a light emission failure for the LPH 7 in FIG. 2, but in step S2 in FIG. This determination is made for the LEDs 721 included in each of the four LPHs 7Y, 7M, 7C, and 7K in FIG.

  Returning to FIG. 3, the description will be continued.

If the occurrence of the light emission failure of the LED 721 is detected for three or more LEDs 721 arranged in succession by the above determination (step S3; Yes), before outputting the image instructed by the user, Based on an instruction from the controller 4, an image quality defect detection pattern described below is output on the paper of the maximum paper size among the three paper sizes stored in the three trays 1 a, 1 b, and 1 c of FIG. Is performed (step S4). Here, the controller 4 corresponds to an example of a control unit according to the present invention.
When three or more LEDs 721 arranged in a row are not detected (step S3; No), the output of the image instructed by the user is executed without outputting the image quality defect detection pattern. As described above, the processing is branched depending on whether or not three or more LEDs 721 arranged in succession are defective in light emission unless the three or more LEDs 721 arranged in succession become defective in light emission. This is because even if the density unevenness occurs due to the LED 721, the image quality defect is hardly recognized by humans.

  Next, the image quality defect detection pattern will be described.

  FIG. 6 shows an image quality defect detection pattern.

  Here, the case where the maximum paper size paper 11 among the three paper sizes stored in the three trays 1a, 1b, and 1c in FIG. 1 is an A3 size paper is illustrated as an example. The image quality defect detection pattern shown in FIG. 6 emits light in step S3 among the four LPHs 7Y, 7M, 7C, and 7K corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (K). A solid image 111 (image with a dot area ratio of 100%) formed over the entire printable area on the paper formed using LPH in which the occurrence of a defect was detected, and the occurrence of a light emission defect was not detected in step S3. Two (two-color) images, which are formed using LPH, are a frame image having a frame 112 representing each area of B4 size, A4 size, and B5 size and a center line 113 representing the center in the short direction. This is an image. Here, the solid image 111 corresponds to an example of a sample image referred to in the present invention. Also, in this figure, a streak-like image quality defect 110 due to a light emission failure of three or more LEDs 721 is shown on the right side of the paper. The area of this image quality defect 110 is a solid image 111 in the solid image 111. This is a white streaky region extending in the longitudinal direction to which no toner adheres.

  Such an image quality defect detection pattern is output for all of the four LPHs in FIG.

  Here, the LPH for forming the frame image is not particularly limited as long as it is formed using the LPH in which the occurrence of the light emission failure is not detected in step S3. For example, the solid image 11 and the frame 112 From the viewpoint of easy identification, black (K) LPH7K, cyan (C) LPH7C, magenta (M) LPH7M, yellow (Y) LPH7Y are prioritized in this order to detect the occurrence of light emission defects. A method of selecting from among LPHs that have not been performed is conceivable. In the image forming apparatus 1000 of FIG. 1, this method is set as a method for selecting an LPH for forming a frame image.

  Although rarely occurs, if the occurrence of a light emission failure is detected for all four LPHs in step S3, the image forming apparatus 1000 uses black (K) for the solid image. Even if there is a possibility that an image quality defect may occur in the frame image, a frame image is formed using black (K) LPH7K, and the above solid image is formed in black (K). The detected image quality defect detection pattern is set so that a frame image is formed with LPH7M of magenta (M) even if there is a possibility that an image quality defect may occur in the frame image.

The user can confirm the position of the image quality defect 110 on the paper 11 by observing the output image quality defect detection pattern. In this figure, it is confirmed that the image quality defect 110 is located inside the B4 size area and outside the A4 size area and the B5 size area. It is recognized that the image quality defect 110 can be prevented from appearing in the image if the image is formed on the size or B5 size paper. Therefore, the user designates the paper size as A4 size or B5 size paper using the operation panel 91 in FIG. 1, and causes the image forming apparatus 1000 to output an image (step S5 in FIG. 3).
At this time, if the tray containing the A4 size paper or the B5 size paper is not in the three trays of FIG. 1, the user replaces the paper in one of the trays with the A4 size paper or the B5 size paper, and then the image. Can be executed. Further, if necessary, the user can designate a reduction ratio of the image by using the operation panel 91 of FIG. 1 and cause the image forming apparatus 1000 to form a reduced image in accordance with the A4 size or the B5 size.

  In the above description, the frame 112 indicating the paper size is output for all paper sizes smaller than the paper size of the image quality defect detection pattern. However, in the present invention, the image quality defect detection pattern is output. Only frames of paper sizes that can be selected at this time (for example, various paper sizes accommodated in a plurality of trays at this time) may be output.

  As described above, the image forming apparatus 1000 forms the image quality defect detection pattern on the paper 11 when the occurrence of the light emission failure is detected, so that the user can emit the light emission failure at any position on the paper due to the light emission failure. It is possible to know whether an image quality defect due to occurrence of the image appears. For this reason, the user can take measures to prevent image quality defects from appearing in the image, such as changing to a smaller paper size or reducing the image, and can continue to form the image desired by the user. Can be prevented from decreasing. In addition, this method is an extremely simple method in which an image quality defect detection pattern is formed on a sheet when the occurrence of a light emission failure is detected, and thus is suitable for cost reduction.

  Actually, methods other than the method described above are also conceivable as methods for avoiding image quality defects from appearing in an image. For example, a defective light emitting diode is detected, and the position of the image portion obtained by the light emission of the defective light emitting diode (that is, actually the position of the image quality defect) is specified on the paper. A method of providing a device that automatically limits the paper size according to the position is conceivable. However, this method requires a large amount of processing to identify the position of the image quality defect, and thus requires an expensive apparatus with high processing capability, which increases the cost of the image forming apparatus. Compared with such a method, the method of the image forming apparatus 1000 that identifies the position of the image quality defect through the output of the image quality defect detection pattern is extremely simple and is a method that is far more suitable for cost reduction.

  Further, the solid image 111 is formed using the LPH in which the occurrence of the light emission failure is detected, and the frame image is formed using the LPH in which the occurrence of the light emission failure is not detected. It is possible to know which paper size is used so that no image quality defect appears in the image without using a measuring instrument.

  Next, another embodiment of the image forming apparatus of the present invention will be described.

  FIG. 7 is an overall configuration diagram of an image forming apparatus according to another embodiment.

  The image forming apparatus 1000 ′ shown in FIG. 7 is different from the image forming apparatus 1000 shown in FIG. 1 in that the image forming apparatus 1000 ′ shown in FIG. 7 reads an image on a sheet and generates an image signal representing the read image. The image forming apparatus 1000 includes the reading device 100. The components other than the reading device are the same as the components of the image forming apparatus 1000 in FIG. Therefore, in FIG. 7, the same components as those of the image forming apparatus 1000 of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

  The reading device 100 includes a reading device main body 100b and a plate-shaped light shielding member 100a that rotates in a direction indicated by a solid double arrow in the figure with a shaft 100c as a rotation axis. The image reading is performed in a state where the sheet on which the image is output is arranged on the reading apparatus main body 100b with the image facing the reading apparatus main body 100b, and the arranged paper is covered with the light shielding member 100a. This is executed by irradiating an image with light from a light source (not shown) in the apparatus main body 100b and generating an image signal representing the intensity of the reflected light. The image signal generated by this reading is input to the controller 4 and is the same as that described with reference to FIG. 1 based on the generated image signal, except that the image has an image quality defect detection pattern described below. An image read on another sheet through an image forming process is newly formed. Accordingly, the image forming apparatus 1000 ′ in FIG. 7 is an image forming apparatus that has the function of a color printer for double-sided output and also has a copy function, like the image forming apparatus 1000 in FIG. 1.

  The image forming apparatus 1000 ′ in FIG. 7 performs the same operation as that of the image forming apparatus 1000 in FIG. 1 until step S3 in FIG. 3, but when the occurrence of a light emission failure of the LED 721 is detected in step S3 (step S3). Yes), the image forming apparatus 1000 ′ in FIG. 7 has the image quality defect detection pattern different from that in FIG. 6 among the three types of paper sizes stored in the three trays 1a, 1b, and 1c. Output on paper.

  FIG. 8 is a diagram illustrating an image quality defect detection pattern output from the image forming apparatus 1000 ′ illustrated in FIG. 7.

  The image quality defect detection pattern shown in FIG. 8 is a solid image 111 that is formed using LPH in which the occurrence of a light emission failure is detected and covers the entire printable area on the paper, and the occurrence of the light emission failure is not detected in step S3. The image is formed by superimposing two (two-color) images, which are formed by using LPH, and a scale image having a scale 11 in the short direction on the paper and a scale 11 having a scale 11 having a scale width. Further, in FIG. 8, a streak-like image quality defect 110 due to the light emission failure of three or more LEDs 721 is shown on the right side of the sheet. The area of the image quality defect 110 is a solid image 111 in the solid image 111. This is a white streaky area where no toner is attached. Due to the image quality defect 110, as shown in the figure, a part of the barcode 11a is lost. The interval between the lines 11b corresponds to the arrangement width of the LEDs 721 in one LED group 720 shown in FIG. 2, and the barcode 11a between the two lines 11b is output between the lines 11b. By indicating what number of LED groups 720 the light is obtained from, the image becomes a scale in the short direction on the paper. The barcode 11a is a barcode that can be read by the reading device 100.

  As in the image forming apparatus 1000 in FIG. 1, in the image forming apparatus 1000 ′ in FIG. 7, the output of the image quality defect detection pattern in FIG. 8 is detected from the four LPHs in FIG. The LPHs that are performed on all the LPHs and form a scale image include black (K) LPH7K, cyan (C) LPH7C, magenta (M) LPH7M, yellow (Y) LPH7Y in the order of priority. Below, it is selected from among LPHs in which no occurrence of light emission failure was detected. If the occurrence of a light emission failure is detected for all four LPHs in step S3, the image forming apparatus 1000 uses the image quality defect detection pattern in which the solid image is formed with black (K). Except for the image quality defect detection pattern in which a frame image is formed using LPH7K of black (K) even if there is a possibility that an image quality defect may occur in the frame image, and the above solid image is formed with black (K), Even if there is a possibility that an image quality defect may occur in the frame image, the frame image is set to be formed by magenta (M) LPH7M.

  When the image quality defect detection pattern shown in FIG. 8 is output, the user causes the reading device 100 to read the image quality defect detection pattern. In the image forming apparatus 1000 ′ of FIG. 7, the image signal generated by reading is input to the controller 4, and the controller 4 recognizes from the image signal that the read image is an image quality defect detection pattern, and performs a copy function. Is stopped and the processing described below is performed. First, the controller 4 obtains the position of the image quality defect 110 on the paper 11 from the position of the barcode 11a partially missing. In addition, the accuracy of the position calculated | required here is an accuracy about the space | interval of the line 11b. Then, the controller 4 determines which paper size of the paper should be used to prevent the image quality defect 110 from appearing in the image. The controller 4 determines the paper size that can be used for image formation. Limit paper sizes to avoid appearing inside. As described above, the image forming apparatus 1000 ′ illustrated in FIG. 7 has a function of reading the image quality defect detection pattern, so that the image forming apparatus 1000 in FIG. The image forming apparatus can be automatically performed.

  If there is no paper size that can prevent the image quality defect 110 from appearing in the image, as in the case where the image quality defect 110 is present near the center of the image, this is indicated on the display screen 90 in FIG. A message is displayed.

  Here, as a modification of the image forming apparatus of FIG. 1 without a reading device, a barcode indicating what number LED group 720 in the image quality defect detection pattern of FIG. An image forming apparatus of a type in which the user himself / herself confirms at which position the image quality defect has occurred by outputting the image quality defect detection pattern replaced with a number representing whether the LED group is the 720th LED group is also included in the present invention. This is an embodiment of an image forming apparatus. In this case, an application is conceivable in which the user informs the support center of the image forming apparatus of the number of the position where the image quality defect has occurred and is informed of the usable paper size. Alternatively, if the controller receives in advance a number at the position where the image quality defect has occurred, it stores a program that restricts the paper size according to the number, and the user simply enters the number to enter the paper size. It is also possible to apply such a restriction.

  Next, still another embodiment of the image forming apparatus of the present invention will be described.

  The image forming apparatus differs from the image forming apparatus 1000 ′ in FIG. 7 in that an image quality defect detection pattern different from that in the image forming apparatus 1000 ′ in FIG. 7 is output. This is the same as the image forming apparatus 1000 ′. Therefore, overlapping description of common points is omitted, and the image quality defect detection pattern output by this image forming apparatus will be described below.

  FIG. 9 is a diagram showing an image quality defect detection pattern output in an image forming apparatus according to still another embodiment of the image forming apparatus of the present invention.

  The image quality defect detection pattern shown in FIG. 9 is a two-dimensional code over the entire printable area on the paper, formed using LPH in which the occurrence of a light emission failure is detected. In FIG. 9, a streak-like image quality defect 110 due to light emission failure of three or more LEDs 721 is shown on the right side of the paper, and the area of this image quality defect 110 is a white streak in which a two-dimensional code is missing. It is a shape area.

  The two-dimensional code adopted as the image quality defect detection pattern is such that even if a part of the two-dimensional code is lost by providing redundancy to the data, the two-dimensional code of the defective part is obtained from information around the defective part. Is a matrix type two-dimensional code of a QR code created so that the contents of the code can be guessed, and an apparatus for reading and analyzing such a matrix type two-dimensional code obtains the position of a missing portion in the two-dimensional code. The two-dimensional code before the loss can be restored. This image quality defect detection pattern uses such a function for determining the position of the missing portion in the two-dimensional code for specifying the position of the image quality defect 110.

  In the image forming apparatus of this embodiment, the reading device reads the image quality defect detection pattern shown in FIG. 9 to generate two-dimensional code data of a two-dimensional code having a streak-like image quality defect 110, and the image of this embodiment It is input to a controller provided in the forming apparatus. As in the image forming apparatus 1000 ′ of FIG. 7, the controller recognizes from the two-dimensional code data that the read image is a two-dimensional code image quality defect detection pattern, stops the copy function, and The process described in is performed. First, the controller 4 obtains the position of the streak-like image quality defect 110 in the short direction on the paper based on the two-dimensional code data. Then, the controller 4 determines which paper size of the paper should be used to prevent the image quality defect 110 from appearing in the image. The controller 4 determines the paper size that can be used for image formation. Limit paper sizes to avoid appearing inside.

  As described above, even when the image quality defect detection pattern of the two-dimensional code is used, as in the case of the image quality defect detection pattern of FIG. 8, the image forming apparatus 1000 of FIG. This can be done automatically by the forming apparatus itself.

  In the image forming apparatus described above, the usable paper size is limited to a paper size that can prevent the image quality defect from appearing in the image, but in the following, the image quality defect appears in the image. An image forming apparatus that changes the electrostatic latent image formation position and the secondary transfer position of the paper so that it can be avoided will be described.

  This image forming apparatus is different from the image forming apparatus 1000 ′ of FIG. 7 in that, after the image quality defect detection pattern is read to determine the position of the image quality defect on the paper, the usable paper size is set as the image quality defect. 7 is to change the formation position of the electrostatic latent image and the secondary transfer position of the sheet instead of limiting to the sheet size that can prevent the image from appearing in the image. Other than this point, the image forming apparatus of FIG. 1000 '. Therefore, overlapping description of common points will be omitted, and the following description will be made on changing the electrostatic latent image formation position and the secondary transfer position of the paper.

  In the image forming apparatus of this embodiment, when the image quality defect detection pattern is read by the reading device provided in the image forming apparatus of this embodiment and the position of the image quality defect on the paper is obtained by the controller, the controller Each of the four LPHs in the forming apparatus (see FIG. 7) gives an instruction to shift the formation position of the electrostatic latent image on each image carrier.

  For example, when the position of the image quality defect is close to the right end as shown in FIG. 8, the LED group in which the LED having the light emission failure exists in the LPH where the occurrence of the light emission failure is detected is the image carrier in the LPH. It is an LED group located in the direction of an end among LED groups arranged in the rotation axis direction. Therefore, instead of using the LED group around the LED group in which the light emission failure is detected, the remaining LED group (that is, the remaining LED group close to the opposite end) is used for forming the electrostatic latent image. An electrostatic latent image can be formed while avoiding the occurrence of image quality defects. The electrostatic latent image formed in this way is formed on the image carrier at a position shifted to the end side more than before. Since the primary transfer image formed on the intermediate transfer belt as described above with reference to FIG. 1 is a multicolor image formed by superimposing the development images of the respective colors, the occurrence of a light emission failure was detected as described above. When the formation position of the electrostatic latent image is shifted with respect to the LPH, the formation position of the electrostatic latent image is similarly shifted with respect to the other LPHs in which the occurrence of defective light emission is not detected. Is required. Therefore, in the image forming apparatus according to this embodiment, when it is detected that three or more LEDs 721 arranged in a row are defective in light emission, the controller avoids an image quality defect from appearing in the image. In addition, an instruction is given to all four LPHs to shift the formation position of the electrostatic latent image on each image carrier.

  In short, shifting the position of forming the electrostatic latent image described above is a normal mode (centering mode) in which the electrostatic latent image is formed in accordance with the center of the roll surface of the image holding body. This corresponds to changing to a mode (right alignment mode or left alignment mode) in which an electrostatic latent image is formed near the end of the roll surface.

  When each electrostatic latent image formed at the shifted position is developed and superimposed on the intermediate transfer belt for primary transfer, the primary transfer image is shifted on the intermediate transfer belt more than usual. It is formed at a position (position approaching the end side of the intermediate transfer belt). In order for the primary transfer image to be secondarily transferred with good position on the conveyed paper, it is also necessary to shift the relative positional relationship between the paper transport path and the intermediate transfer belt. Therefore, in the image forming apparatus of this embodiment, at the timing when the sheet passes the registration roll (same as the registration roll pair 8 in FIG. 7), the registration roll pair is in the roll axis direction of the registration roll pair (that is, in the middle) Thus, the secondary transfer onto the sheet is performed in a state where the sheet conveyance path is shifted in the width direction of the intermediate transfer belt. Hereinafter, the mechanism will be described.

  FIG. 10 is a schematic diagram showing a mechanism for shifting the paper transport path.

  The registration roll pair 8 shown in FIG. 10 has a first registration roll 81 on the back side in FIG. 10 and a second registration roll 82 on the near side in the figure. As shown by the horizontal arrow in the figure, the sheet 11 conveyed from the left in the figure passes between the first registration roll 81 and the second registration roll 82.

  Here, the first registration roll 81 is provided with a roll shaft 810 that serves as a rotation axis when the first registration roll 81 rotates. As shown in the figure, the roll shaft 810 includes a roll shaft 810. A gear 12c having teeth extending in a direction orthogonal to the axial direction is in contact. Here, the gear 12c is integrated with a rotational force transmission shaft 12b that receives the rotational driving force of the motor 12a and rotates in the direction indicated by the wide double arrow B in the drawing. For this reason, the gear 12c rotates with the rotation of the rotational force transmission shaft 12b, and the rotation of the gear 12c causes the first registration roll 81 together with the roll shaft 810 to move in the direction of the solid double arrow C in the vertical direction in the figure.

  As described above, the controller controls the motor 12a shown in FIG. 10 to cause the four LPHs to shift the formation position of the electrostatic latent image, thereby controlling the motor 11a in FIG. By rotating the motor 12a at the timing of passing between the first registration roll 82 and the first registration roll 82, the first registration roll 81 is subjected to secondary transfer on the sheet in accordance with the position of the primary transfer image on the intermediate transfer belt. And the second registration roll 82 are moved in the width direction of the intermediate transfer belt. By such control of the controller, the secondary transfer position of the sheet is changed in accordance with the change of the formation position of the electrostatic latent image.

  In the image forming apparatus according to this embodiment, even when the image formation defect is present near the center of the image, even if the electrostatic latent image formation position or the secondary transfer position of the paper is changed, the image quality defect is imaged. If it cannot be avoided that the image appears inside, a message indicating that effect is displayed on the display screen as in the image forming apparatus of FIG.

  In this embodiment, after the image quality defect detection pattern of FIG. 8 is read and the position of the image quality defect on the sheet is obtained, the electrostatic latent image formation position and the sheet secondary transfer position are changed. However, instead of the image quality defect detection pattern of FIG. 8, the position of the image quality defect on the paper is obtained by reading the two-dimensional code of FIG. An image forming apparatus that changes the next transfer position is also an embodiment of the image forming apparatus of the present invention. Such an embodiment is different from the above-described embodiment having the mechanism for shifting the paper conveyance path in FIG.

  In each of the embodiments including the above-described reading device, the image quality defect position is grasped only by causing the reading device to read an image in which the image quality defect detection pattern and the scale image are superimposed or to read a two-dimensional code. Measures are automatically taken to avoid the output of an image with image quality defects, such as limiting the size of the paper and changing the formation position of the electrostatic latent image and the secondary transfer position of the paper. As a result, in these embodiments, in order to avoid the output of an image with image quality defects, a convenient image forming apparatus that saves the user's effort is realized.

1 is an overall configuration diagram of an image forming apparatus according to an exemplary embodiment. FIG. 2 is a diagram illustrating a schematic configuration of an LPH provided in the image forming apparatus illustrated in FIG. 1. 2 is a flowchart showing an operation flow when the image forming apparatus in FIG. 1 outputs an image quality defect detection pattern. It is the schematic diagram showing the detection circuit 722 which detects the presence or absence of LED with poor light emission. It is a figure showing the signal input / output in this detection circuit at the time of detection of LED with poor light emission. It is a figure showing the image quality defect detection pattern. FIG. 6 is an overall configuration diagram of an image forming apparatus according to another embodiment. FIG. 8 is a diagram illustrating an image quality defect detection pattern output in the image forming apparatus of FIG. 7. It is a figure showing the image quality defect detection pattern output in the image forming apparatus of another embodiment of the image forming apparatus of this invention. FIG. 5 is a schematic diagram illustrating a mechanism for shifting a paper transport path.

Explanation of symbols

1000, 1000 '... Image forming apparatus,
1a, 1b, 1c ... tray,
2 ... Output tray,
3a ... first conveying roll pair,
3b ... 2nd conveyance roll pair,
3c ... the third conveyance roll pair,
4 ... Controller,
5 ... Intermediate transfer belt,
50K, 50C, 50M, 50Y ... primary transfer roll,
5a ... Driving roll,
61K, 61C, 61M, 61Y, 61 ... image carrier,
64K, 64C, 64M, 64Y ... developer,
65K, 65C, 65M, 65Y ... charging member,
7K, 7C, 7M, 7Y, 7 ... LPH,
71 ... Condensing part,
710 ... Selfoc lens,
72 ... light emitting part,
720 ... LED group,
721 ... LED,
721a: LED input terminal,
721b ... LED control signal terminal,
721c ... LED output terminal,
722 ... a detection circuit,
7221: First resistance,
7222: Second resistance,
7223 ... Input signal amplifier,
7223a ... 1st terminal,
7223b ... the second terminal,
7224... Output signal amplifier,
7224a ... Output terminal,
8 ... Registrole vs.
81. First register roll,
810: Roll axis,
82 ... the second cashier roll,
8a ... Sending roll pair,
8b ... the first pair of conveying rolls for both sides,
8c ... 2nd conveyance roll pair for double sides,
8d ... the third pair of conveyance rolls for both sides,
9: Secondary transfer roll pair,
10: fixing device,
11 ... paper,
11a Bar code,
11b ... line,
110 ... Image quality defect,
111 ... Solid image,
112 ... frame,
113 ... Center line,
12a ... motor,
12b ... rotational force transmission shaft,
12c: gears,
13 ... 4th conveyance roll pair,
90 ... display screen,
91 ... Control panel,
100 ... reading device,
100a ... light shielding member,
100b ... reading device body,
100c ... axis

Claims (6)

A paper transport unit for transporting paper,
An exposure unit that includes a plurality of light emitting elements arranged in the width direction intersecting the paper conveyance direction, and forms an electrostatic latent image by performing exposure according to an image signal;
A developed image forming unit for developing the electrostatic latent image formed by the exposure unit to form a developed image;
An image forming unit that forms an image on the paper by transferring and fixing the developed image formed by the developed image forming unit on the conveyed paper;
A detection unit for detecting that a light emission failure has occurred in the exposure unit;
When the detection unit detects the occurrence of a light emission failure, the image signal indicates a sample image for image quality defect detection to the exposure unit and instructs to print over the entire printable area on the paper A control unit that forms an electrostatic latent image by performing exposure according to the image, forms a developed image of the electrostatic latent image in the developed image forming unit, and forms the sample image on a sheet in the image forming unit An image forming apparatus comprising:
In the image forming apparatus, a set of the exposure unit, the developed image formation unit, and the detection unit is divided into four colors of C (cyan) color, M (magenta) color, Y (yellow) color, and K (black) color. 4 sets corresponding to each color,
The control unit forms a developed image representing the sample image in a group to which an exposure unit in which the occurrence of a light emission failure is detected belongs among the four sets, and the occurrence of a light emission failure is not detected in the plurality of sets. A development image representing a frame image having a frame representing a plurality of types of paper sizes is formed in a set to which the exposure unit belongs, and a development image representing the sample image and a development representing the frame image are further formed in the image formation unit. The images are superimposed and transferred and fixed on the paper.
Among the four exposure units corresponding to the four colors, as an exposure unit used for forming the developed image representing the frame image, a black (K) exposure unit, a cyan (C) exposure unit, and magenta (M ) Exposure unit and yellow (Y) exposure unit in this order of priority, and the control unit determines, in accordance with the priority order, the frame from among the exposure units in which no occurrence of light emission failure has been detected. An image forming apparatus, wherein an exposure unit used for forming the developed image representing an image is selected, and the developed image representing the frame image is formed in a group to which the selected exposure unit belongs . A paper transport unit for transporting paper,
An exposure unit that includes a plurality of light emitting elements arranged in the width direction intersecting the paper conveyance direction, and forms an electrostatic latent image by performing exposure according to an image signal;
A developed image forming unit for developing the electrostatic latent image formed by the exposure unit to form a developed image;
An image forming unit that forms an image on the paper by transferring and fixing the developed image formed by the developed image forming unit on the conveyed paper;
A detection unit for detecting that a light emission failure has occurred in the exposure unit;
When the occurrence of a light emission failure is detected by the detection unit, the exposure unit is an image signal that represents a sample image for detecting an image quality defect and instructs to print over the entire printable area on the paper Control that causes exposure according to a signal to form an electrostatic latent image, forms a developed image of the electrostatic latent image in the developed image forming unit, and forms the sample image on the paper in the image forming unit An image forming apparatus comprising:
In the image forming apparatus, a set of the exposure unit, the developed image formation unit, and the detection unit is divided into four colors of C (cyan) color, M (magenta) color, Y (yellow) color, and K (black) color. 4 sets corresponding to each color,
The control unit forms a developed image representing the sample image in a group to which an exposure unit in which the occurrence of a light emission failure is detected belongs among the four sets, and the occurrence of a light emission failure is not detected in the plurality of sets. A development image representing a scale image having a scale arranged at a predetermined interval is formed in a set to which the exposure unit belongs, and a development image representing the sample image and a development image representing the scale image are superimposed on the image formation unit. Transfer / fix on paper,
Among the four exposure parts corresponding to the four colors, as an exposure part used for forming the developed image representing the scale image, an exposure part of black (K), an exposure part of cyan (C), and magenta (M ) Exposure unit and yellow (Y) exposure unit in this order of priority, and the control unit is arranged according to the priority order from the exposure units in which no occurrence of light emission failure is detected. Selecting an exposed portion used for forming the developed image representing an image, and forming the developed image representing the scale image in a group to which the selected exposed portion belongs,
An image reading unit that reads an image recorded on paper and generates an image signal;
Position identification for identifying an image quality defect position on the paper on which the image quality defect has occurred based on an image signal generated by reading the image on the paper on which the sample image and the scale image are superimposed in the image reading unit And an image forming apparatus. When the detection unit detects that a light emission failure has occurred in all four exposure units corresponding to the four colors, the control unit is formed by the set to which the black (K) exposure unit belongs. The frame image to be superimposed on the developed image of the sample image is formed in a group to which the magenta (M) exposure unit belongs, and the remaining three exposures excluding the black (K) exposure unit among the four exposure units. 2. The frame image to be superimposed on the developed image of the sample image formed by the three groups to which the respective sections belong, is formed in the group to which the black (K) exposure section belongs . Image forming apparatus. When the detection unit detects that a light emission failure has occurred in all four exposure units corresponding to the four colors, the control unit is formed by the set to which the black (K) exposure unit belongs. The scale image to be superimposed on the developed image of the sample image is formed in a group to which the magenta (M) exposure unit belongs, and the remaining three exposures of the four exposure units excluding the black (K) exposure unit. 3. The image according to claim 2 , wherein the scale image to be superimposed on the developed image of the sample image formed by the three groups to which the respective sections belong is formed in the group to which the black (K) exposure section belongs. Forming equipment. Based on the image quality defect position specified by the position specifying unit, the image forming unit includes a size limiting unit that limits the size of the paper on which the image forming unit transfers and fixes an image to the size of the paper that can prevent the occurrence of the image quality defect. The image forming apparatus according to claim 2 , wherein the image forming apparatus is an image forming apparatus. The control unit shifts the electrostatic latent image in the width direction so as to avoid occurrence of image quality defects based on the image quality defect position specified by the position specifying unit, and relatively controls the width direction. The image forming apparatus according to claim 2 , wherein the image forming apparatus transfers the image onto a sheet whose position has been adjusted.

Images