JP2018092114A - Image forming apparatus - Google Patents

Abstract

As a measure for preventing the formation of an image having white lines or dark lines due to an apparatus abnormality, it is possible to suppress unnecessary notification to a user of occurrence of white lines or dark lines. .
Based on detection results by an image density sensor for a plurality of locations of a first test toner image formed on an image forming means comprising a photosensitive developing unit, an optical writing unit, and the like, the plurality of locations. The image forming conditions of the image forming means are corrected so as to suppress the image density deviation in each, and the second test toner image is formed on the image forming means under the corrected image forming conditions. The control unit 50 is configured to determine the presence or absence of a streak-like image density abnormality portion based on the detection result by the image density sensor 18.
[Selection] Figure 3

Description

  The present invention relates to an image forming apparatus.

  Conventionally, a measure for determining the presence or absence of a streaky image density abnormal portion in a test toner image formed by the image forming means and preventing the formation of an image having the streaky image density abnormal portion based on the determination result An image forming apparatus that implements the above is known.

  For example, an image forming apparatus described in Patent Document 1 uses image density (toner adhesion amount) at a plurality of locations in a test toner image formed by an electrophotographic image forming unit and transferred to the surface of an intermediate transfer belt. Detection is performed by an optical sensor serving as a density detection means. Based on the detection result, the presence / absence of a white streak as a streak-like image density abnormality portion in the test toner image is determined. After that, when there is a white streak, as a countermeasure, the fact that a white streak (abnormality) has occurred is displayed on the operation panel unit to notify the user or the image forming operation is interrupted. It is said that the user can eliminate white streaks by placing an order for repair of the device according to the display.

  However, this image forming apparatus may unnecessarily implement measures for preventing the formation of an image having a streak-like image density abnormality portion.

  In order to solve the above-described problems, the present invention has an image density detecting unit that detects an image density at a plurality of locations of an image forming unit that forms a toner image and a test toner image that is formed on the image forming unit. Control means for determining the presence or absence of a streak-like image density abnormality portion in the test toner image based on the result, and implementing measures for preventing the occurrence of the streaky image density abnormality portion based on the determination result; In the image forming apparatus, the image density shift at each of the plurality of locations is suppressed based on the detection result by the image density detection means for the plurality of locations of the first test toner image formed on the image forming device. The image forming condition of the image forming means is corrected, and the image forming means forms a second test toner image under the corrected image forming condition. Based on the detection result by the serial image density detection unit, so as to determine the presence or absence of streak-like image density anomaly, it is characterized in that constitutes the control means.

  According to the present invention, there is an excellent effect that unnecessary measures for preventing the formation of an image having a streaky image density abnormality portion can be suppressed.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. FIG. 2 is a schematic configuration diagram of a printing apparatus of the image forming apparatus. FIG. 2 is a block diagram showing a main part of an electric circuit of the image forming apparatus. FIG. 2 is a schematic configuration diagram illustrating an image density sensor of the printing apparatus. FIG. 2 is a perspective view showing the image density sensor from a lower side with a part of an intermediate transfer belt. The schematic block diagram which shows the image density sensor of the state which opened the shutter member. The schematic block diagram which shows the image density sensor of the state which closed the shutter member. K test toner image It-K, C test toner image It-C, M test toner image It-M, and Y test toner image It-Y formed on the front surface of the intermediate transfer belt are transferred to the intermediate transfer belt. FIG. 6 is a graph showing the relationship between the position in the main scanning direction and the image density in the first test toner image It ₁ . Graph showing the relationship between the position and the image density in the main scanning direction in the second test toner image It _2. 6 is a flowchart illustrating a processing flow of a regular routine process performed by a control unit of the image forming apparatus. 6 is a graph showing an example of the relationship between the image density and the position in the sub-scanning direction when an image density defect occurs in the photosensitive member rotation cycle. 6 is a flowchart illustrating a processing flow of condition determination processing and print job processing performed by a control unit of an image forming apparatus according to a specific example. FIG. 3 is a schematic diagram illustrating a first example of an inquiry screen displayed on a display unit of the image forming apparatus. FIG. 3 is a plan view for explaining the relationship between the position of white stripes and dark stripes generated on an intermediate transfer belt in the image forming apparatus and the size of a recording sheet. The schematic diagram which shows the 2nd example of the inquiry screen displayed on the display part. The schematic diagram which shows the 3rd example of the inquiry screen displayed on the display part. The schematic diagram which shows the 4th example of the inquiry screen displayed on the display part.

Hereinafter, an embodiment of an image forming apparatus to which the present invention is applied will be described.
First, a basic configuration of the image forming apparatus according to the embodiment will be described. FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. In the figure, the image forming apparatus is shown from the front side. In FIG. 1, the image forming apparatus includes a printing apparatus A, a sheet supply apparatus B, a sheet conveying unit C, a switchback apparatus D, an image reading apparatus E, and the like.

  FIG. 2 is a schematic configuration diagram of a printing apparatus A that forms an image on a recording sheet. The printing apparatus A includes photosensitive developing units 6Y, 6M, 6C, and 6K for forming toner images of yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K). Above the photosensitive developing units 6Y, 6M, 6C, 6K, there is an optical writing unit 20 for writing an electrostatic latent image by irradiating the surface of the photoreceptors 1Y, 1M, 1C, 1K with laser light L. It is arranged.

  A transfer unit 7 having an endless intermediate transfer belt 8 is disposed below the photosensitive developing units 6Y, 6M, 6C, and 6K. In addition to the intermediate transfer belt 8, the transfer unit 7 includes a plurality of stretching rollers disposed inside the loop, a tension roller disposed outside the loop, a belt cleaning device 14, an image density sensor 18, a secondary transfer. It has a counter roller 41 and the like. As the tension roller inside the loop, the primary transfer rollers 9Y, 9M, 9C, and 9K, the driven roller 10, the drive roller 11, the secondary transfer roller 12, the cleaning counter roller 13, the detection position roller 17, and the like are disposed. ing.

  The intermediate transfer belt 8 is moved endlessly in the clockwise direction in the drawing by the rotation of the driving roller 11 that is driven to rotate in the clockwise direction in the drawing by the driving means.

  The primary transfer rollers 9Y, 9M, 9C, and 9K disposed inside the loop of the intermediate transfer belt 8 sandwich the intermediate transfer belt 8 between the photoreceptors 1Y, 1M, 1C, and 1K. As a result, primary transfer nips for Y, M, C, and K in which the front surface of the intermediate transfer belt 8 and the photoreceptors 1Y, 1M, 1C, and 1K abut are formed. The primary transfer rollers 9Y, 9M, 9C, and 9K are each applied with a primary transfer bias having a polarity opposite to the charging polarity of the toner by a primary transfer power source. As a result, a primary transfer electric field is formed in the primary transfer nip for Y, M, C, and K to electrostatically move the toner from the photoreceptors 1Y, 1M, 1C, and 1K to the intermediate transfer belt 8 side.

  A secondary transfer counter roller 41 is disposed below the intermediate transfer belt 8. The secondary transfer counter roller 41 is in contact with the portion of the intermediate transfer belt 8 that is wound around the secondary transfer roller 12 from the belt front surface side to form a secondary transfer nip. A secondary transfer bias having the same polarity as the charging polarity of the toner is applied to the secondary transfer roller 12 by a secondary transfer power source. On the other hand, the secondary transfer counter roller 41 is grounded. As a result, a secondary transfer electric field for electrostatically moving the toner from the belt surface side to the secondary transfer counter roller 41 side is formed in the secondary transfer nip.

  The photosensitive developing units 6Y, 6M, 6C, and 6K use toners of different colors (Y, M, C, and K), but the other configurations are the same. For example, a photosensitive developing unit 6Y that forms a Y toner image includes a charging device 2Y, a developing device 5Y, a drum cleaning device 4Y, and a charge eliminating device around a drum-shaped photosensitive member 1Y as a latent image carrier. Etc.

  The charging device 2Y uniformly charges the surface of the photoreceptor 1Y that rotates counterclockwise in the drawing to a high potential having the same polarity as the toner. The surface of the photoreceptor 1 </ b> Y after uniform charging carries an electrostatic latent image for Y by optical scanning using laser light L. This electrostatic latent image is developed into a Y toner image by the developing device 5Y that performs development using a Y developer containing Y toner and a magnetic carrier. Then, it enters the primary transfer nip for Y as the photoconductor 1Y rotates, and is primarily transferred to the front surface of the intermediate transfer belt 8 by the action of the nip pressure and the primary transfer electric field. Transfer residual toner adhering to the surface of the photoreceptor 1Y after passing through the primary transfer nip is removed from the surface of the photoreceptor 1Y by the drum cleaning device 4Y.

  The Y photosensitive developing unit 6Y has been described, but in the M, C, and K photosensitive developing units 6M, 6C, and 6K, M toner images are formed on the surfaces of the photoreceptors 1M, 1C, and 1K by the same electrophotographic process. , C toner image and K toner image are formed.

  The intermediate transfer belt 8 sequentially passes through the primary transfer nips for Y, M, C, and K along with the endless movement in the clockwise direction in the drawing. Then, the Y toner image, M toner image, C toner image, and K toner image on the photoreceptors 1Y, 1M, 1C, and 1K are sequentially superimposed and transferred primarily. As a result, a four-color superimposed toner image is formed on the front surface of the intermediate transfer belt 8.

  The four-color superimposed toner image enters the secondary transfer nip as the intermediate transfer belt 8 moves endlessly. On the right side of the secondary transfer nip in the figure, a registration roller pair 42 of a sheet conveyance unit C described later is disposed. The recording sheet P is conveyed to the registration nip of the registration roller pair 42 at the timing when the four-color superimposed toner image is formed on the intermediate transfer belt 8. The registration roller pair 42 starts to rotate at a timing at which the recording sheet P can be synchronized with the four-color superimposed toner image on the belt at the secondary transfer nip, and sends the recording sheet P toward the secondary transfer nip. On the recording sheet P that has entered the secondary transfer nip, the four-color superimposed toner image on the intermediate transfer belt 8 is secondarily transferred to a full-color toner image by the action of the nip pressure and the secondary transfer electric field.

  On the left side of the secondary transfer nip in the drawing, there is disposed a sheet conveyance belt device 15 that moves the sheet conveyance belt 15a stretched by the driving roller 15c and the driven roller 15b endlessly in the counterclockwise direction in the drawing. ing. The recording sheet P that has passed through the secondary transfer nip is conveyed toward the fixing device 16 while being held on the front surface of the sheet conveying belt 15a of the sheet conveying belt device 15.

  The fixing device 16 forms a fixing nip by contact between a fixing roller 16a including a heat source such as a halogen lamp and a pressure roller 16b pressed toward the fixing roller 16a. When the recording sheet P sent to the fixing device 16 passes through the fixing nip, the full color toner image is fixed on the surface by the action of the nip pressure or heating.

  In FIG. 1, the sheet supply apparatus B includes a first storage unit 31 and a second storage unit 32 that store a plurality of recording sheets P in a sheet bundle state. In addition, the recording sheet P in the first storage unit 31 is sent out from the first storage unit 31 and separated one by one, and the recording sheet P in the second storage unit 32 is stored in the second. A second feeding / separating section 34 that feeds out from the section 32 and separates the sheets one by one is also provided. Furthermore, a feeding path 35 for feeding the recording sheet P that has passed through the feeding separation unit to the sheet conveying unit C is also provided.

  The image reading device E includes a scanner that reads an image of a document placed on a contact glass, and an automatic document feeder (ADF) that automatically conveys a sheet-like document to an image reading position by the scanner. . The image information read by the image reading device E is sent to the printing device A, and the printing device A forms an image based on the sent image information on the recording sheet P. Thereby, it is possible to perform image copy of the document. The printing apparatus A can also form an image based on image information sent from a personal computer or an image based on image information sent via a FAX line.

  The sheet conveyance unit C includes a secondary transfer counter roller 41, a registration roller pair 42, an inlet conveyance path 43, a discharge path 44, a reverse path 45, a retransmission path 46, a separation claw 47, a reverse roller pair 48, and the like. The sheet conveyance unit C receives the recording sheet P fed from the sheet supply device B in its own entrance conveyance path 43 and conveys it toward the registration roller pair 42. After the recording sheet P abuts on the registration nip of the registration roller pair 42 to correct the skew, the recording sheet P is fed to the secondary transfer nip by driving the registration roller pair 42.

  Thereafter, when the recording sheet P on which the toner image has been fixed is sent from the fixing device 16, the sheet conveying unit C receives the recording sheet P on the separation claw 47 and adjusts the posture of the swingable separation claw 47. Thus, the subsequent conveyance destination of the recording sheet P is adjusted. Specifically, when the recording sheet P is discharged outside the apparatus, the posture of the separation claw 47 is adjusted so that the recording sheet P enters the discharge path 44. Then, the recording sheet P that has entered the discharge path 44 is discharged outside the apparatus.

  On the other hand, the sheet conveying unit C causes the recording sheet P to enter the reversing path 45 when it is necessary to form a toner image on the second surface of the recording sheet P on which the toner image is fixed only on the first surface. The posture of the separation claw 47 is adjusted as described above. Thus, after the recording sheet P is received in the reversing path 45, the recording sheet P is switched back in cooperation with the switchback device D described later, and then sent to the retransmission path 46. The recording sheet P sent to the retransmission path 46 is sent to the discharge path 44 after the toner image is fixed on the second surface through the entrance conveyance path 43, the secondary transfer nip, and the fixing device 16 in this order. Discharged outside.

  When the jam of the recording sheet P occurs in the sheet conveying unit C, the sheet conveying unit C slides from the rear side toward the front side of the image forming apparatus so that the jammed recording sheet P can be easily taken out. It can be moved and pulled out. It is pulled out from the back side of the paper surface of FIG.

  FIG. 3 is a block diagram illustrating a main part of an electric circuit of the image forming apparatus according to the embodiment. In the figure, a control unit 50 as control means has a CPU, RAM, ROM, nonvolatile memory and the like. The control unit 50 is electrically connected with toner density sensors of Y, M, C, and K developing devices 5Y, 5M, 5C, and 5K. Accordingly, the control unit 50 grasps the toner concentrations of the Y developer, M developer, C developer, and K developer in the Y, M, C, and K developing devices 5Y, 5M, 5C, and 5K. Can do. Then, in accordance with the toner density detection result, the Y, M, C, and K toner replenishing devices are driven to supply appropriate amounts of Y toner, M toner, C toner, and K toner to the developing devices 5Y, 5M, 5C, and 5K. To replenish. As a result, even if the Y developer, M developer, C developer, and K developer in the developing devices 5Y, 5M, 5C, and 5K decrease the toner concentration with development, the toner concentration is set to a target value. Revive.

  The controller 50 is also electrically connected to Y / M / C / K unit detachment sensors 53Y, 53M, 53C, and 53K. Unit attachment / detachment sensors 53Y, 53M, 53C, and 53K as attachment / detachment detection means detect that the photosensitive developing units 6Y, 6M, 6C, and 6K have been removed from the printing apparatus A, and indicate that they have been attached to the printing apparatus A. Can be detected. Accordingly, the control unit 50 can grasp that the photosensitive developing units 6Y, 6M, 6C, and 6K have been attached to and detached from the printing apparatus A.

  Further, Y, M, C, and K developing power supplies 54Y, 54M, 54C, and 54K are also electrically connected to the control unit 50. The controller 50 can individually adjust the values of the developing biases output from the developing power supplies 54Y, 54M, 54C, and 54K by individually outputting control signals to the developing power supplies 54Y, 54M, 54C, and 54K, respectively. it can. That is, the values of the developing bias applied to the developing sleeves of the developing devices 5Y, 5M, 5C, and 5K for Y, C, M, and K can be individually adjusted.

  The developing sleeve is a cylindrical non-magnetic pipe that encloses a magnet roller, and conveys the developer to a developing position facing the photoreceptor while carrying the developer on its surface as it rotates. This contributes to development. In the image forming apparatus according to the embodiment, the surfaces of the photoreceptors 1Y, 1M, 1C, and 1K are uniformly charged negatively by the charging devices 2Y, 2M, 2C, and 2K to form a background portion on the surface. Then, an electrostatic latent image is formed by attenuating the potential of the light irradiation area by the optical writing unit 20 in the background, and the absolute value is a value between the absolute value of the background potential and the absolute value of the electrostatic latent image. Is applied to the developing sleeve. As a result, a developing potential for electrostatically moving the toner from the sleeve side to the electrostatic latent image side acts between the electrostatic latent image and the developing sleeve, and the toner is placed between the background portion and the developing sleeve on the background portion side. Apply the ground potential to move electrostatically from the sleeve to the sleeve side.

  Y, M, C, and K charging power supplies 55Y, 55M, 55C, and 55K are also electrically connected to the controller 50. The control unit 50 individually controls the charging bias values output from the charging power supplies 55Y, 55M, 55C, and 55K by individually outputting control signals to the charging power supplies 55Y, 55M, 55C, and 55K. be able to. That is, the values of the charging bias applied to the charging rollers of Y, C, M, and K charging devices 2Y, 2M, 2C, and 2K can be individually adjusted.

  Further, a belt posture solenoid 61 is also electrically connected to the control unit 50. This belt posture solenoid 61 changes the posture of the side plate holding the bearings of the primary transfer rollers 9Y, 9M, and 9C for Y, M, and C so that the primary transfer rollers 9Y and Y for Y, M, and C are changed. 9M and 9C are displaced. The intermediate transfer belt 8 is moved toward and away from the Y, M, and C photoconductors 1Y, 1M, and 1C by changing the stretching posture of the intermediate transfer belt 8 along with the displacement. When executing a monochrome mode print job, the intermediate transfer belt 8 is separated from the Y, M, and C photoconductors 1Y, 1M, and 1C. On the other hand, when a full color mode print job is executed, the intermediate transfer belt 8 is brought into contact with all the Y, M, C, and K photoconductors 1Y, 1M, 1C, and 1K.

  In addition, a K process motor 56 and a color process motor 60 are also electrically connected to the control unit 50. The K process motor 56 is a motor serving as a drive source for rotationally driving various members in the K photosensitive developing unit 6K. The color process motor 60 is a motor serving as a drive source for rotationally driving various members in the Y, M, and C photosensitive developing units 6Y, 6M, and 6C. When executing a monochrome mode print job, the control unit 50 rotates only the K process motor 56 of the two process motors. In contrast, when a full color mode print job is executed, each of the two process motors is driven to rotate.

  The control unit 50 includes a write control unit 51, a transfer motor 57, a registration motor 58, a paper feed motor 59, an environmental sensor 62, a primary transfer power source 63, a secondary transfer power source 64, an image density sensor 18, and optical writing. The unit 20 and the like are also electrically connected.

  The writing control unit 51 controls the driving of the optical writing unit 20 based on image data sent from an external scanner or personal computer, and performs optical scanning on the photoreceptors 1Y, 1M, 1C, and 1K. . The received image data is sent to the control unit 50.

  The environment sensor 62 detects the temperature and humidity in the machine. The transfer motor 57 is a motor that is a drive source for the drive roller 11 and the intermediate transfer belt 8. The registration motor 58 is a motor that is a drive source of the registration roller pair 42. The paper feed motor 59 is a motor that is a drive source for the paper feed system. The primary transfer power source 63 individually outputs primary transfer biases applied to the primary transfer rollers 9Y, 9M, 9C, and 9K for Y, M, C, and K, respectively. The secondary transfer power source 64 outputs a secondary transfer bias applied to the secondary transfer roller 12.

  The controller 50 outputs Y, M, C, and K control signals individually to the primary transfer power supply 63, thereby performing primary transfer for Y, M, C, and K output from the primary transfer power supply 63. The bias value can be individually controlled. Further, by outputting a control signal to the secondary transfer power source 64, the value of the secondary transfer bias output from the secondary transfer power source 64 can be controlled.

  The control unit 50 is also electrically connected to an operation display unit 65 that functions as an information notification unit or an information input unit. An operation display unit having a display unit including a touch panel and an input unit including a numeric keypad can notify the user of various information by displaying various information on the touch panel. In addition, information input to the numeric keypad or the like by a user operation can be received.

  FIG. 4 is a schematic configuration diagram showing the image density sensor 18. In the figure, the image density sensor 18 includes a light source 18a, a lens array 18b, an image sensor array 18c, a detection window 18d made of transparent glass, a shutter member 18e, a white reference plate 18f, and the like.

  The shutter member 18e can reciprocate along the belt movement direction by driving the actuator, and opens and closes the detection window 18d with the reciprocation. In the figure, the shutter member 18e is retracted from directly below the detection window 18d and the detection window 18d is exposed.

  Examples of the white reference plate 18f include those made of Lumirror E20 (trade name), which is a white film manufactured by Toray Industries, Inc. The white reference plate 18f is fixed to the back surface of the shutter member 18e by a double-sided tape or the like, and reciprocates along the belt moving direction together with the shutter member 18e.

  As the light source 18a, a light emitting element provided at the end of the light guide or an LED array can be used. Although the light source 18a emits white light, a light source that individually emits R light, G light, and B light may be provided, and white light may be obtained by mixing these lights.

  As the lens array 18b, a SELFOC (registered trademark) lens can be exemplified. The imaging element array 18c includes a plurality of image sensors arranged in an array. Each image sensor individually receives R (red) light, G (green) light, and B (blue) light imaged by the lens array 18b, and outputs a signal corresponding to each light. A CMOS sensor, a CCD sensor, or the like is used as the imaging element array 18c.

  Examples of the image density sensor 18 include a contact image sensor (CIS). As shown in FIG. 5, the image density sensor 18 has its longitudinal direction along the width direction of the intermediate transfer belt 8 and a predetermined gap on the front surface (loop outer surface) of the intermediate transfer belt 8. It arrange | positions so that it may oppose. The dimension in the longitudinal direction of the image density sensor 18 is larger than the dimension in the width direction on the intermediate transfer belt 8. As a result, the image density sensor 18 can individually detect the image density of each pixel in the entire area in the longitudinal direction of a test toner image described later formed on the front surface of the intermediate transfer belt 8. Even if the size of the image density sensor 18 in the longitudinal direction is not made larger than the belt width, the following is possible if the size of the effective image area in the belt width direction is made equal to or greater than that. That is, the image density sensor 18 can detect the image density of each pixel in the entire area in the longitudinal direction of the test toner image.

  In the image density sensor 18, the arrangement direction of the plurality of image sensors and the longitudinal direction of the entire sensor are the same direction. As shown in FIG. 6, the image density of the test toner image It formed on the intermediate transfer belt 8 can be detected with the detection window 18d opened. When the image density is not detected by the image density sensor 18, as shown in FIG. 7, the shutter member 18e is moved directly below the detection window 18d by the control of the control unit to shield the detection window 18d. Thereby, it is possible to suppress the dirt from adhering to the detection window 18d.

  When the shutter member 18e is closed, the image density sensor 18 cannot detect the image density of the test toner image It on the intermediate transfer belt 8, but the white reference plate 18f fixed to the back surface of the shutter member 18e. The image density can be detected.

  Unlike a simple reflective optical sensor, the image density sensor 18 can capture a test toner image or the like with a high resolution of 300 to 1200 [dpi]. Unlike the conventional configuration in which the image density in a patch-like test part of several centimeters square is detected by a reflection type optical sensor, the image density is detected even in a test part having a small millimeter angle. It is possible. Therefore, the size of each test portion can be reduced, and the test toner image It can be downsized.

  The control unit 50 performs a shading correction data construction process during the first operation after factory shipment. In this shading data construction process, shading correction data is constructed based on image data obtained by causing the image density sensor 18 to detect the image density of each pixel of the white reference plate 18f. Specifically, in a state where no dirt is attached to the white reference plate 18f and the detection window 18d, theoretically, each pixel of the image data obtained by reading the white reference plate 18f is read as white. It should be. For example, the gradation of R, G, B of each pixel is expressed by an 8-bit natural number, and 200 to 255 of 0 to 255 are treated as 200 uniformly (with an upper limit of 200), 201 gradations of 0 to 200 Suppose that gradation is expressed by. In this case, if there is no dirt on the white reference plate 18f or the detection window 18d, the pixel values of the pixels of the image data obtained by reading the white reference plate 18f are all (R = 200, G = 200, B = 200). However, in actuality, the pixel value of each pixel slightly varies due to the sensitivity error of the image element of the image line sensor and the unevenness of the light emission amount of the light source 18a. Then, the density unevenness is erroneously detected as it is. Therefore, in order to prevent this erroneous detection of density unevenness, correction data for recognizing that all pixels are white is constructed as shading correction data.

  In the image forming apparatus according to the embodiment, streaky image density abnormal portions may be generated in an image due to device abnormality. The abnormal portion of the image density is an image density that is remarkably lighter or darker than the original image density, and has a streak shape extending in the sub-scanning direction of the image. The sub-scanning direction is a direction along the surface moving direction of the photoreceptors 1Y, 1M, 1C, and 1K and the intermediate transfer belt 8, and corresponds to the moving direction of the image in the image forming apparatus. On the other hand, the main scanning direction is a direction along the rotational axis direction of the photoreceptors 1Y, 1M, 1C, and 1K, and is also a direction orthogonal to the sub-scanning direction.

  The control unit 50 determines the presence or absence of a streak-like image density abnormality portion in the test toner image, and periodically performs processing for notifying the user when there is a streak-like image density abnormality portion. . FIG. 8 shows a K test toner image It-K, a C test toner image It-C, an M test toner image It-M, and a Y test formed on the front surface of the intermediate transfer belt 8 during this process. FIG. 4 is a diagram illustrating a toner image It-Y together with an intermediate transfer belt 8 and an image density sensor 18.

  As shown in the figure, each color test toner image (It-K, It-C, It-M, It-Y) is formed in a rectangular shape extending in the belt width direction. Although it is not the length over the entire belt width, it is the same length as the effective image area in the belt width direction.

  In the figure, among the test toner images of the respective colors, white streak ws as a streak-like image density abnormality portion occurs in the K test toner image It-K. The white stripe ws is a streak-like image density abnormal portion formed at an image density that is significantly lower than the original image density. If dirt adheres to the dust-proof glass serving as the light emitting portion in the optical writing unit 20, or if foreign matter is mixed in the developer in the developing device (for example, 5Y), as shown in the figure, the sub-scanning direction (FIG. White stripes ws extending in the middle arrow direction may occur.

  Also, in the figure, among the test toner images of the respective colors, a dark streak ds as a streak-like image density abnormality portion is generated in the Y test toner image It-Y. The dark streak ds is a streak-shaped image density abnormal portion formed with an image density significantly higher than the original image density. A dark streak ds extending in the sub-scanning direction may be generated as shown in the figure due to a cause such as contamination on the charging roller of the charging device (for example, 2Y).

  When the above-described processing is started, the control unit 50 forms the test toner images of the respective colors, and then, for each of the pixels arranged in the sub-scanning direction in the image data obtained by capturing each test toner image with the image density sensor. Obtain the image density. Then, based on the image density of each pixel, the presence / absence of white streak ws or dark streak ds in the test toner image of each color is determined. To do. Specifically, a message such as “A white streak has occurred at K. Please request repair to the maintenance organization” is displayed on the operation display unit 65 including a touch panel, etc. The occurrence of an abnormal image density location, the color, etc. are notified.

  According to this configuration, when a streak-like image density abnormality portion occurs, the control unit 50 promptly detects the occurrence of the image density abnormality portion and notifies the user, thereby prompting a quick repair order. Thereby, it is possible to shorten the period from the occurrence of an abnormal image density location to the completion of repair for eliminating the cause.

  However, if a streak-like image density defect that can be suppressed by adjusting the image forming conditions of the image forming means is erroneously detected as an abnormal image density point, although it is caused by a factor different from the device abnormality (device failure), In contrast, unnecessary repair orders are misleaded. For example, the charging roller has electric resistance unevenness in the rotation axis direction, and in some areas in the rotation axis direction of the photoconductor, the background potential is higher than in other areas. The image density may be thinner than other areas, resulting in streak-like image density defects. The image density defect can be suppressed, for example, by making the optical writing intensity (laser power) at the time of optical scanning, which is an image forming condition, stronger in other areas than in the aforementioned partial areas. Nevertheless, if it is erroneously detected as a white stripe ws and notified to the user, an unnecessary repair order will be misleaded.

  In this image forming apparatus, the combination of the optical writing unit 20 and the photosensitive developing units 6Y, 6M, 6C, and 6K for each color functions as an image forming unit that forms a toner image.

Next, a characteristic configuration of the image forming apparatus according to the embodiment will be described.
Based on the image data obtained by imaging the second test toner image It ₂ formed on the intermediate transfer belt 8 for each of the colors Y, M, C, and K, the control unit 50 has a streak-like image density. Determine if there is an abnormal part. However, prior to this determination, a streak-like shape extending in the sub-scanning direction is based on image data obtained by imaging the first test toner image It ₁ formed on the intermediate transfer belt 8 by the image density sensor 18. The presence / absence of an image density defect is determined. In this determination, when it is determined that there is an image density defect, the image forming condition is corrected so as to suppress the image density defect. Specifically, the optical writing intensity at the time of optical scanning with respect to the region corresponding to the streak in the streak-like image density defect among the entire region in the rotation axis direction (main scanning direction) of the photosensitive member is set to the optical writing with respect to the other region. Correction to make it larger or smaller than the included strength is performed. More specifically, in the case of an image density defect in which the image density is lower at the streak portion than at the other portions, correction is performed to make the former optical writing intensity larger than the latter optical writing intensity. Thereby, only the image density of the streak portion is made higher. On the other hand, in the case of an image density defect in which the image density is higher at the streak portion than at the other portions, correction is performed to make the former optical writing intensity smaller than the latter optical writing intensity. As a result, only the image density at the streak portion is made thinner.

FIG. 9 is a graph showing the relationship between the position in the main scanning direction and the image density in the first test toner image It ₁ . The control unit 50 determines the image density of each pixel (each position) in the main scanning direction of the first test toner image It ₁ based on the image data obtained by imaging the first test toner image It ₁ with the image density sensor 18. Is obtained, the average value thereof is obtained. Then, it is determined whether the deviation amount from the average value of the image density of each pixel exceeds the threshold value α.

In the illustrated example, the image density of the pixels existing in the area A ₁ in the main scanning direction of the first test toner image It ₁ is higher than the average value, and the deviation amount of the image density exceeds the threshold value α. Yes. This is in the region A _1, which means that the portion which is the image density plethora streak has occurred. The part may be an image density defect that can be suppressed by adjusting the image forming conditions, or may be a streak-like image density abnormality part due to an apparatus abnormality. If it is a streaky image density abnormal part, it is necessary to repair the device to suppress it, but if the image density is poor, it can be suppressed by adjusting the image forming conditions without repairing the device. It is.

In the illustrated example, the image density of the pixels existing in the area A ₂ in the main scanning direction of the first test toner image It ₁ is lower than the average value, and the deviation amount of the image density sets the threshold value α. Over. This is in the area A _2, which means that the portion that is a insufficient image density in streak has occurred. The part may be an image density defect that can be suppressed by adjusting the image forming conditions, or may be a streak-like image density abnormality part due to an apparatus abnormality. If it is a streaky image density abnormal part, it is necessary to repair the device to suppress it, but if the image density is poor, it can be suppressed by adjusting the image forming conditions without repairing the device. It is. As described above, the image forming condition to be adjusted is the optical writing intensity during optical scanning.

When there is a pixel whose deviation amount from the average value of the image density exceeds the threshold value α, the control unit 50 performs photosensitivity corresponding to the pixel in the main scanning direction so that the image density of the pixel approaches the average value. The optical writing intensity for the pixels on the body surface is corrected. For example, in the example of FIG. 9, the optical writing intensity at the time of optical scanning with respect to each pixel on the photoreceptor surface corresponding to each pixel existing in the area A _{1 of} the first test toner image It ₁ is made lower than usual. Thus, the image density at each pixel is further lowered. Further, by increasing the optical writing intensity at the time of optical scanning with respect to each pixel on the surface of the photoreceptor corresponding to each pixel existing in the area A _{2 of} the first test toner image It ₁ , The image density at is higher.

When the optical writing intensity is corrected in this way, if the streak generated in the first test toner image It ₁ is an image density defect that can be suppressed by adjusting the optical writing intensity, the toner to be imaged thereafter The streaks should be suppressed in the image.

Therefore, the control unit 50, Y, M, C, for each of the colors K, After correcting the optical writing intensity as needed based on the image density of each pixel of the first test toner image It _1, then Then, the second test toner image It ₂ is formed. Then, it is determined that the second test toner image It ₂ based on the image data obtained by imaging by the image density sensor 18, the presence or absence of streak-like image density anomaly extending in the sub-scanning direction.

Figure 10 is a graph showing the relationship between the position and the image density in the main scanning direction in the second test toner image It _2. When the control unit 50 obtains the image density of each pixel in the main scanning direction of the second test toner image It ₂ based on the image data obtained by imaging the second test toner image It ₂ with the image density sensor 18, The average value is obtained. Then, it is determined whether the deviation amount from the average value of the image density of each pixel exceeds the threshold value α. The threshold value α is the same value as the threshold value α in FIG.

In the illustrated example, each of the image density of all pixels existing in a region A ₁ in the second test the main scanning direction of the toner image It ₂ is higher than the average value, either the amount of deviation of image density It is below the threshold value α. This means that in the area A ₁ , the portion where the first test toner image It ₁ has a streaky image density defect is no longer the image density defect in the second test toner image It ₂ . In other words, what occurred in the area A ₁ of the first test toner image It ₁ was not a streak-shaped image density abnormal portion due to a device abnormality but a streak-shaped image density defect that could be suppressed by adjusting the optical writing intensity. It was.

On the other hand, it has both image density of each pixel existing in the region A ₂ in the second test the main scanning direction of the toner image It ₂ is lower than the average value. Then, but not all the pixels existing in the area A _2, the deviation amount from the mean value of the image density of a portion of the pixel exceeds the threshold again alpha. A portion where the image density is insufficient in a streak form so as to be visible is still left. This means that the portion is not a streak-like image density defect that can be suppressed by adjusting the optical writing intensity, but a streak-like image density abnormality portion caused by a device abnormality.

Control unit 50, in the second test toner image It _2, when a stripe-like image density deviation exceeding the threshold α is recognized, determines it as a a stripe-like image density anomaly. Specifically, when the image density is lower than the average value, the image density abnormal portion is determined to be a white stripe ws. When the image density is higher than the average value, the abnormal image density portion is determined to be a dark streak ds. In the illustrated example, stripe-like image density deviation caused in the area A ₂ is determined to be white streaks ws.

An example of determining the presence or absence of an image density defect based on the determination result of whether or not the image density deviation amount of each image in the first test toner image It ₁ and the second test toner image It ₂ exceeds the threshold value α. Although described, it may be as follows. That is, the presence / absence of an image density defect may be determined based on the determination result of whether or not the threshold value α is greater than or equal to the threshold value α.

  By the way, since the image density of the solid toner image is a considerably high value, even if a pixel in which the toner adhesion amount per unit area is larger than the surrounding area is generated, the image density at that pixel is excessive. Is inconspicuous. This means that in a solid toner image, it is difficult to detect an image density defect having an excessive image density. On the other hand, when a pixel having a toner adhesion amount that is insufficient as compared with the surrounding area is generated, an insufficient image density is easily noticeable in the pixel. This means that, in a solid toner image, an image density defect that is insufficient in image density is easily noticeable. That is, in the solid toner image, it is possible to accurately detect the white stripe ws due to insufficient image density.

  On the other hand, since the image density of the halftone toner image still has a sufficient margin to reach the saturation density, if a pixel having a larger toner adhesion amount than the surroundings occurs, the image density at that pixel is excessive. Is easy to stand out. This means that in a halftone toner image, an image density defect that is excessive in image density is easily noticeable. That is, in the halftone toner image, it is possible to accurately detect the dark streak ds due to excessive image density.

Therefore, the control unit 50 creates the following two images as the first test toner images It ₁ of the respective colors Y, M, C, and K. The first is a solid first test toner image bIt ₁ in which toner is attached to all the pixels in the image portion. The second is a halftone first test toner image hIt ₁ that reproduces a halftone by area gradation that does not cause toner to adhere to some pixels of the image portion. That, Y, M, C, for each of the colors K, a high concentration first test toner image serving as a solid first test toner images BIT _1, a low concentration first test toner image serving as a halftone first test toner images HIT ₁ And image.

Further, the control unit 50 determines whether or not the image density of each pixel is lower than the average value based on the image data obtained by imaging the solid first test toner image bIt ₁ with the image density sensor 18. . If it is low, it is determined whether or not the deviation amount from the average value exceeds the threshold value α. If it exceeds the threshold value, it is determined that the pixel is a pixel causing insufficient image density. . The image data is not used as data for determining the presence or absence of excessive image density. With such a configuration, it is possible to detect an insufficient image density with higher accuracy than in the case where the presence or absence of an image density is determined based on the image density of each pixel of the halftone first test toner image hIt ₁ .

Further, the control unit 50 determines whether the image density of each pixel is higher than the average value based on the image data obtained by imaging the halftone first test toner image hIt ₁ with the image density sensor 18. To do. If it is high, it is determined whether or not the amount of deviation from the average value exceeds the threshold value α. If it exceeds the threshold value, the pixel is determined to be a pixel causing an excessive image density abnormality. To do. The image data is not used as data for determining the presence or absence of an image density deficiency abnormality. In such a configuration, it is possible to detect an excessive image density abnormality with higher accuracy than when determining the presence or absence of an excessive image density abnormality based on the image density of each pixel of the solid first test toner image bIt ₁ .

In addition, the control unit 50 creates the following two images as the second test toner images It ₂ of the respective colors Y, M, C, and K. The first is a solid second test toner image bIt ₂ having the same image density as the solid first test toner image bIt ₁ . The second is a halftone second test toner image hIt ₂ having the same image density as the halftone first test toner image hIt ₁ . That, Y, M, C, for each of the colors K, a high concentration second test toner image serving as a solid second test toner images BIT _2, low density second test toner image serving as a halftone second test toner images HIT ₂ And image.

Further, the control unit 50 determines whether or not the image density of each pixel is lower than the average value based on the image data obtained by imaging the solid second test toner image bIt ₂ by the image density sensor 18. . If it is low, it is determined whether or not the deviation amount from the average value exceeds the threshold α, and if it exceeds, the pixel causing the image density deficiency abnormality, that is, the white streak is determined. It is determined that the pixel is ws. The image data is not used as data for determining the presence / absence of an excessive image density abnormality. In such a configuration, the presence or absence of the white streak ws can be accurately determined as compared with the case where the presence or absence of an image density deficiency abnormality is determined based on the image density of each pixel of the halftone second test toner image hIt ₂ .

Further, the control unit 50 determines whether or not the image density of each pixel is higher than the average value based on the image data obtained by imaging the halftone second test toner image hIt ₂ by the image density sensor 18. To do. If it is high, it is determined whether or not the deviation amount from the average value exceeds the threshold value α. If the threshold value is exceeded, the pixel causing the excessive image density abnormality, that is, the dark streak is determined for the pixel. It is determined that the pixel is ds. The image data is not used as data for determining the presence or absence of an image density deficiency abnormality. With such a configuration, the presence or absence of the dark streak ds can be accurately determined as compared with the case where the presence or absence of an excessive image density abnormality is determined based on the image density of each pixel of the solid second test toner image bIt ₂ .

FIG. 11 is a flowchart showing a processing flow of the regular routine processing executed by the control unit 50.
The flow in the first half of this routine routine corrects the optical writing intensity at the time of optical scanning with respect to the corresponding pixel on the photoconductor so that the image density of the pixel in which the image density is excessive or insufficient approaches the target density. It is a flow of processing. Since the image density of each image changes with time due to various factors, it is desirable to perform this processing at a regular timing according to the change timing.

  Also, the flow in the latter half of the regular routine processing shown in the figure is a processing flow for determining whether or not white streak ws or dark streak ds due to device abnormality has occurred, and displaying an error if necessary. . Since white stripes ws and dark stripes due to device abnormalities are less frequently generated than time-dependent fluctuations in image density, it is desirable that the execution frequency of the latter half of the flow be lower than that of the first half. This is because, if the same execution frequency is used, the downtime of the apparatus due to frequent execution of the latter half flow unnecessarily occurs.

Therefore, in this image forming apparatus, the execution trigger of the first half flow is set as the condition x, while the execution trigger of the second half flow is set as the condition x + condition y. Regarding the condition x, the condition x is satisfied when any of the following (1) to (5) is satisfied.
(1) The cumulative number of prints since the end of the first half of the flow has reached a predetermined number.
(2) The elapsed time from the end of the first half flow has reached a predetermined value.
(3) The amount of change in absolute humidity since the first half flow exceeded a predetermined threshold.
(4) The power was turned on after the power-off state continued for a predetermined time.
(5) The standby time waiting for the next print command has reached a predetermined value.

  In addition, the condition y is satisfied when the number of pixels on the photoconductor whose optical writing intensity is corrected in the first half of the flow is equal to or greater than a predetermined value.

The control unit 50 that has started the regular routine first waits until the condition x is satisfied (N in step 1; hereinafter, step is denoted as S). When the condition x is satisfied (Y in S1), the solid first test toner image bIt ₁ and the halftone first test toner image hIt ₁ are imaged and imaged (S2). Next, for each pixel of the solid first test toner image bIt ₁ , it is determined whether or not the image density is insufficient (whether or not the deviation amount of the image density less than the average value exceeds the threshold value α) (S3). Further, based on the determination result, the presence or absence of streaks due to insufficient image density in the solid first test toner image bIt ₁ is determined (S4). Thereafter, when there is no streak (N in S4), immediately, when there is a streak (Y in S4), the optical writing intensity at the time of optical scanning for the pixel on the photoconductor corresponding to the streak is set to a stronger value. After the correction (S5), the process proceeds to S6 described later. It should be noted that in S4, streaks due to insufficient image density occur when more than the number of pixels corresponding to the image density deviation amount less than the average value exceeds the threshold value α in each of the main scanning direction and the sub-scanning direction. judge.

In step S6, the presence or absence of excessive image density (whether or not the deviation amount of the image density exceeding the average value exceeds the threshold value α) is determined for each pixel of the halftone first test toner image hIt ₁ . Next, based on the determination result, the presence / absence of streaks due to excessive image density in the halftone first test toner image hIt ₁ is determined (S7). Thereafter, when there is no streak (N in S7), immediately, when there is a streak (Y in S7), the optical writing intensity at the time of the optical operation on the pixel on the photoconductor corresponding to the streak is corrected to a weaker value. Then (8), the process proceeds to S9 described later. In S7, streaks due to excessive image density occur when more than the number of pixels in which the deviation amount of the image density exceeding the average value exceeds the threshold value α corresponds to each in the main scanning direction and the sub scanning method. judge.

  In step S9, it is determined whether or not the above-described condition y is satisfied. If not satisfied (N in S9), a series of processing flow is returned to S1. On the other hand, if satisfied (Y in S9), the process proceeds to the latter half of the flow after S10.

In step S10, the solid second test toner image bIt ₂ and the halftone second test toner image hIt ₂ are imaged and imaged. Thereafter, it is determined whether or not the image density is insufficient for each pixel of the solid second test toner image bIt ₂ (S11). Then, based on the determination result, the presence / absence of white stripe ws in the solid second test toner image bIt ₂ is determined (S12). Next, if there is no white streak ws (N in S12), immediately if there is a white streak ws (Y in S12), the white streak flag is set (S13), and then the process proceeds to S14.

In S14 in step determines whether the image density excess for each pixel of the halftone second test toner images HIT _2. Next, based on the determination result, it is determined whether or not there is a dark streak ds in the halftone second test toner image hIt ₂ (S15). Then, if there is no dark streak ds (N in S15), the dark streak flag is set (S16) if there is a dark streak ds (Y in S15), and then the process proceeds to S17.

  In step S17, it is determined whether at least one of the white streak flag and the dark streak flag is being set. Then, when it is not set (N in S17), immediately, when it is being set (S18), an error message corresponding to the mode of the flag is displayed on the operation display unit 65 to notify the user, and then a series of Is returned to step S1.

  In the process of S18, when only the white streak flag is being set out of the two flags, for example, “A white streak has occurred in a color image. Please request repair to the service organization.” Is displayed. Further, when only the dark streak flag is being set, for example, an error message “A dark streak has occurred in a color image. Please request repair to the service organization” is displayed. If both flags are set, for example, an error message “White streaks and dark streaks have occurred in the color image. Please request repair to the service organization” is displayed.

  It should be noted that, for some of the colors Y, M, C, and K, the condition y is obtained when the optical writing intensity is corrected in the first half of the flow and the number of pixels on the photoconductor exceeds a predetermined value. If is satisfied, the following may be performed. That is, instead of performing the latter half of the flow for all of Y, M, C, and K, the latter half of the flow may be performed for only some of the colors described above.

  Further, when the condition y is satisfied only for the color desired by the user by the setting operation of the user, the latter half of the flow may be performed.

  As an example of a measure for preventing the occurrence of white stripes ws and dark stripes ds, an example of prompting the user to make a repair request to the maintenance organization has been described. However, the measure is not limited to this. Any countermeasure may be used so that the image forming apparatus is inspected. For example, a business trip inspection may be automatically requested from a maintenance organization by communication using a telephone line. Moreover, you may display the message which urges implementation of an inspection, displaying the figure and text explaining a detailed inspection work with respect to a user.

[Example]
Next, an example in which a more characteristic configuration is added to the image forming apparatus according to the embodiment will be described. Unless otherwise specified below, the configuration of the image forming apparatus according to the example is the same as that of the embodiment.

  The control unit 50 of the image forming apparatus according to the embodiment periodically generates in the sub-scanning direction in addition to determining the presence or absence of white stripes ws and dark stripes ds extending in the sub-scanning direction in the regular routine processing. The presence / absence of a periodic density abnormal portion, which is an image density abnormal portion, is also determined. The periodic density abnormal part is generated at the photosensitive member rotation period due to local scratches or deterioration of the photosensitive member surface, and is generated at the sleeve rotation period due to local scratches on the developing sleeve surface. There are things to do. There are also cases where the charging roller rotation cycle occurs due to local damage or deterioration of the charging roller surface. When these periodic density abnormalities occur, it is necessary to place an order for repair to replace the photoconductor, developing sleeve, charging roller, and the like that are the cause.

  However, unlike the above-described periodic density abnormalities, an image density defect that may be suppressed by adjusting the imaging conditions may occur although it occurs at the rotation cycle of the roller or sleeve. For example, when the developing gap between the photosensitive member and the developing sleeve fluctuates due to an outer diameter error or eccentricity of the photosensitive member or the developing sleeve, an image density defect occurs in the photosensitive member rotation period or the developing sleeve rotation period. In addition, image density defects may occur in the charging roller rotation period due to uneven charging of the photoreceptor due to uneven electrical resistance in the circumferential direction of the charging roller. These image density defects can be suppressed by periodically changing the developing bias and the charging bias. Nevertheless, if such image density defects are erroneously detected as periodic density abnormalities and notified to the user, unnecessary repair requests are misleaded.

Therefore, the control unit 50 corrects the periodic variation pattern of the developing bias and the charging bias, which are image forming conditions, so as to suppress periodic image density defects for the periodic density abnormal portion, and then determines whether there is a periodic density abnormal portion. It is supposed to be. Specifically, the presence / absence of a periodic image density defect in the sub-scanning direction is determined based on image data obtained by imaging the solid first test toner image bIt ₁ . The first test toner image It ₁ and the second test toner image It ₂ are as follows so that an image density defect occurring at any one of the photosensitive member rotation period, the developing sleeve rotation period, and the charging roller rotation period can be detected. Create something like this. The length in the sub-scanning direction is larger than any of the photosensitive member circumferential length, the developing sleeve circumferential length, and the charging roller circumferential length.

  If there is a periodic image density defect in the solid first test toner image, pattern data for generating a development bias change that suppresses the image density defect is constructed. For example, when there is an image density defect that occurs in the photosensitive member rotation cycle, photosensitive member rotation cycle pattern data for changing the developing bias in the photosensitive member rotation cycle is constructed so as to cancel it. In addition, when there is an image density defect that occurs in the developing sleeve rotation cycle, sleeve rotation cycle pattern data for changing the developing bias in the developing sleeve rotation cycle is constructed so as to cancel it. In addition, when there is an image density defect that occurs in the charging roller rotation cycle, charging cycle pattern data for varying the developing bias in the charging roller rotation cycle is constructed so as to cancel it. Thereafter, in the image forming process, the development bias is periodically changed based on the pattern data.

  For reference, FIG. 12 shows an example of the relationship between the image density and the position in the sub-scanning direction when an image density defect occurs during the photosensitive member rotation period.

  Note that the development bias cycle variation according to the photosensitive member rotation cycle pattern data is performed based on the timing at which the photosensitive member rotation posture detection sensor detects that the photosensitive member has reached the reference rotation posture. Further, the development bias period variation according to the sleeve rotation period pattern data is performed based on the timing at which the development sleeve rotation attitude detection sensor detects that the development sleeve has reached the reference rotation attitude. Further, the development bias cycle variation according to the charging cycle pattern data is performed based on the timing at which the charging roller rotation posture detection sensor detects that the charging roller has reached the reference rotation posture. In addition, when two or more periodic pattern data are followed, fluctuations due to them are superimposed.

For solid toner images, the image density can be adjusted by adjusting the developing bias. Therefore, each periodic variation pattern data for periodically varying the developing bias is constructed based on the periodic image density defect of the solid first test toner image bIt ₁ .

On the other hand, the image density of a halftone toner image can be adjusted by adjusting the charging bias. Therefore, the control unit 50 determines the presence / absence of a periodic halftone image density defect in the sub-scanning direction based on image data obtained by imaging the halftone first test toner image hIt ₁ . Then, when there is a periodic halftone image density defect, periodic pattern data for generating a charging bias change that suppresses the halftone image density defect is constructed. For example, when there is a half-toe image density defect that occurs in the photosensitive member rotation cycle, photosensitive member rotation cycle pattern data for changing the charging bias in the photosensitive member rotation cycle is constructed so as to cancel it. Further, when there is a halftone image density defect that occurs in the developing sleeve rotation cycle, sleeve rotation cycle pattern data for changing the charging bias in the developing sleeve rotation cycle is constructed so as to cancel out the halftone image density defect. In addition, when there is a halftone image density defect that occurs in the charging roller rotation cycle, charging cycle pattern data for changing the charging bias in the charging roller rotation cycle is constructed so as to cancel it. Thereafter, in the image forming process, the charging bias is periodically changed based on the pattern data.

  In the halftone as well, the periodic variation of the charging bias according to the photosensitive member rotation cycle pattern data is performed based on the timing at which the photosensitive member rotation posture detection sensor detects that the photosensitive member has become the reference rotation posture. . Further, the periodic variation of the charging bias according to the sleeve rotation cycle pattern data is performed based on the timing at which the developing sleeve rotation posture detection sensor detects that the developing sleeve has reached the reference rotation posture. Further, the periodic variation of the charging bias according to the charging cycle pattern data is performed based on the timing at which the charging roller rotation posture detection sensor detects that the charging roller has reached the reference rotation posture. In addition, when two or more periodic pattern data are followed, fluctuations due to them are superimposed.

After the periodic pattern data is constructed as described above, when the condition y is satisfied, the presence / absence of a periodic concentration abnormality portion is determined in the latter half flow described above. Specifically, based on the result of determining the presence or absence of insufficient image density for each pixel of the solid second test toner images BIT _2, the existence of periodic concentration anomaly serving cycle white spots in the solid second test toner image BIT ₂ judge. If there is periodic whiteout, after setting the periodic whiteout flag, an error message indicating that periodic whiteout has occurred is displayed (periodic whiteout prevention measures).

Then, based on the result of determining the presence or absence of image density excess for each pixel of the halftone second test toner images HIT _2, determining the presence or absence of the periodic concentration anomaly serving periodic concentration excess in the halftone second test toner images HIT ₂ To do. Then, if there is excessive periodic concentration, after setting the excessive periodic concentration flag, an error message indicating that there is excessive periodic concentration is displayed (measure for preventing excessive periodic concentration).

  In such a configuration, it is possible to mislead unnecessary repair orders to the user while shortening the period from the occurrence of periodic white spots and excessive periodic concentration to the completion of repairs to eliminate the cause. Can be suppressed.

A first test toner image It ₁ and a second test toner image It ₂ for detecting white stripes ws and dark stripes ds extending in the sub-scanning direction, and a first test toner for extracting periodic density abnormal portions The image It ₁ and the second test toner image It ₂ are the same. That is, by using the same combination of the first test toner image It ₁ and the second test toner image It ₂ , the detection of the white stripe ws and the dark stripe ds and the detection of the periodic density abnormal portion are performed.

As described above, the lengths of the first test toner image It ₁ and the second test toner image It _{2 in} the sub-scanning direction are made larger than any of the photosensitive member circumferential length, the developing sleeve circumferential length, and the charging roller circumferential length. Thus, it is possible to detect periodic density unevenness that occurs in the period of the circumference. Further, the lengths of the first test toner image It ₁ and the second test toner image It _{2 in} the main scanning direction are made substantially the same as the length of the photosensitive member in the rotation axis direction. As for the white stripe ws and the dark stripe ds, the image density of the first test toner image It ₁ and the second test toner image It ₂ at predetermined positions in the sub-scanning direction is grasped at predetermined intervals in the main scanning direction. To do. Then, based on these image densities, an average value of the image density in the main scanning direction and a deviation amount from the average value of the image density at each predetermined interval are obtained.

Further, for the periodic density abnormal portion in the sub-scanning direction, the image density at each predetermined interval in the sub-scanning direction is set for a predetermined position in the main scanning direction of the first test toner image It ₁ and the second test toner image It _2. To grasp. Then, based on the image density, an average value of the image density in the sub-scanning direction and a deviation amount from the average value of the image density at each predetermined interval are obtained.

  Note that when the control unit 50 sets the white streak flag, dark streak flag, periodic whiteout flag, and excessive periodic density flag described above, the flag is canceled by a user who has performed component replacement or a manual operation by a service person. . The flag information is stored in the non-volatile memory so that the set flag is not cleared even when the power is turned off.

[Concrete example]
Next, a specific example in which a further characteristic configuration is added to the image forming apparatus according to the embodiment will be described. Unless otherwise specified, the configuration of the image forming apparatus according to the specific example is the same as that of the embodiment.

  All of the image forming apparatuses according to the embodiments, examples, and specific examples are configured to set the image forming position by the center reference method. In the center reference method, regardless of the page size on which an image is reproduced, the center position in the main scanning direction of the page (agreement with the recording sheet P) is the center position in the rotation axis direction (main scanning direction) of the photosensitive member. It is a method to match.

  The image forming apparatus according to the specific example can output an image on a recording sheet P having an A3 size at the maximum. For this reason, the length in the width direction of the intermediate transfer belt 8 is slightly larger than the length in the short direction of the A3 size. When an image is formed on an A3 size recording sheet P, the recording sheet P is conveyed in a posture in which the longitudinal direction of the sheet is aligned with the sheet conveying direction, and the center of the recording sheet P in the short direction is The transfer belt 8 is aligned with the center in the width direction. Similarly, for the B4 size recording sheet P slightly smaller than the A3 size, the center in the width direction of the sheet is aligned with the center in the width direction of the intermediate transfer belt 8. On the other hand, the recording sheet P of A4 size or B5 size slightly smaller than this is transported in a posture in which the sheet lateral direction is aligned with the sheet transport direction. Then, the center in the longitudinal direction of the sheet is aligned with the center in the width direction of the intermediate transfer belt 8.

  When the control unit 50 of the image forming apparatus according to the specific example sets the above-described white streak flag, in which position the white streak ws occurs in the entire area in the width direction (main scanning direction) of the intermediate transfer belt 8. The white stripe position information indicating is stored in the nonvolatile memory. Further, when the above-described dark streak flag is set, dark streak position information indicating in which position the dark streak ds occurs in the entire area in the width direction of the intermediate transfer belt 8 is stored in the nonvolatile memory.

  FIG. 13 is a flowchart illustrating a processing flow of condition determination processing and print job processing performed by the control unit 50 of the image forming apparatus according to the specific example. In the figure, a series of flow of S3, S4, and S5 is a print job processing flow. The other flow is the condition determination process. This condition determination process is a process for determining whether or not a print job can be executed. Depending on the determination result, even if a print command is issued, the series of flows is terminated without executing the print job.

  The control unit 50 that has started the condition determination process first waits until there is a print command (N in S1). When a print command is issued by the user (Y in S1), it is next determined whether or not an abnormality flag is being set in any of Y, M, C, and K (S2). . The name of the abnormality flag is a general term for the above-described white streak flag, dark streak flag, periodic whiteout flag, and excessive periodic density flag. If at least one of these four colors is being set, it is determined in step S2 that the abnormality flag is being set.

  When the abnormality flag is not set in all of Y, M, C, and K (N in S2), the image density abnormality portion does not occur in all the colors. Therefore, the control unit 50 shifts from the condition determination process to the print job process in order to execute the print job based on the print command received in S1.

  In the print job process, first, a print job is started by starting driving of each device (S3). Thereafter, when printing of all pages is completed (Y in S4), the print job is terminated by stopping the driving of each device (S5), and the print job processing is completed. Thereafter, the series of processing flow is returned to S1, and the next print command is waited.

  On the other hand, if there is at least one color that sets at least one of the four abnormal flags such as the white stripe flag and the dark stripe flag among Y, M, C, and K (Y in S2). The controller 50 determines whether or not the abnormality flag in the set includes a period abnormality flag (S6). The period abnormality flag is a general term for the above-described period blank flag and period density excess flag. If at least one periodic abnormality flag is present among the abnormality flags being set, it is determined in step S6 that there is a periodic abnormality flag (Y in S6).

  If there is a periodic abnormality flag being set (Y in S6), periodic white spots or excessive periodic density will occur in at least one of Y, M, C, and K colors. These periodic density abnormalities occur as unevenness in the sub-scanning direction of the sheet surface in synchronization with the rotation cycle of the photosensitive member, the developing sleeve, or the charging roller. It occurs at intervals of about [cm]. Normally, the length of the recording sheet P to be used in the sub-scanning direction is larger than the interval, so that unevenness is inevitably generated on the surface of the recording sheet P as periodic white spots or excessive periodic density. Resulting in. That is, when the periodic abnormality flag is being set, it is inevitable that a periodic density abnormality is generated on the surface of the recording sheet P.

  Therefore, when there is a periodic flag being set (Y in S6), the control unit 50 performs a process for inquiring the user whether or not an abnormal image density location (periodic density abnormality) may be generated. (S7). Specifically, as shown in FIG. 14, a message in which there is a high possibility that a periodic density abnormality location is generated and an inquiry matter regarding whether or not printing can be performed is displayed on the display unit of the operation display unit 65. (Touch panel) 65a is displayed. When the user who confirms the display presses the OK button displayed on the display unit and inputs information indicating permission (Y in S8 in FIG. 13), the control unit 50 starts from the condition determination process. The process proceeds to print job processing (S3 to S5) to execute the print job. On the other hand, when information indicating that permission is not permitted is input (N in S8), a message “print execution canceled” is displayed on the display unit 65a of the operation display unit 65 (S9). A series of processing flow is returned to S1.

  On the other hand, if there is no periodic abnormality flag among the set abnormality flags (N in S6), the periodic abnormality flag being set is the white streak flag, the dark streak flag, or both. In other words, white stripes ws, dark stripes ds, or both are generated on the intermediate transfer belt 8. However, although these white stripes ws and dark stripes ds are generated on the surface of the intermediate transfer belt 8, they may not be secondarily transferred onto the surface of the recording sheet P. For example, in the example shown in FIG. 15, the white stripe ws and the dark stripe ds on the intermediate transfer belt 8 are secondarily transferred to the recording sheet P of A3 size or A4 size, but the recording sheet of B4 size or B5 size is used. No secondary transfer on P.

  The example shown in FIG. 15 will be described in more detail. In FIG. 15, white stripes ws and dark stripes ds are generated near the end of the intermediate transfer belt 8 in the width direction (main scanning direction). The occurrence position overlaps the short-side end portion of the A3 size recording sheet P that is brought into close contact with the intermediate transfer belt 8 at the secondary transfer nip and the long-side end portion of the A4 size recording sheet P. For this reason, white stripes ws and dark stripes ds generated on the intermediate transfer belt 8 are secondarily transferred to the recording sheet P of A3 size or A4 size. That is, the stripe on the belt is reflected on the recording sheet P of A3 size or A4 size. Therefore, the positions where white stripes ws and dark stripes ds are generated in the entire area of the intermediate transfer belt 8 in FIG. 15 are the positions of white stripes ws and A4 when the recording sheet P of A3 size or A4 size is used. This corresponds to the transfer position where the dark stripe ds is secondarily transferred to the recording sheet P.

  On the other hand, the occurrence position of white streak ws or dark streak ds in the main scanning direction on the intermediate transfer belt 8 does not overlap with the B4 size or B5 size recording sheet that is brought into close contact with the intermediate transfer belt 8 at the secondary transfer nip. For this reason, white stripes ws and dark stripes ds generated on the intermediate transfer belt 8 are not secondarily transferred to the recording sheet P of B4 size or B5 size. That is, the stripe on the belt is not reflected on the recording sheet P of B4 size or B5 size. Therefore, the position where the white stripe ws and the dark stripe ds are generated in the entire area of the intermediate transfer belt 8 in FIG. 15 is the white stripe ws or the position where the B4 size or B5 size recording sheet P is used. This corresponds to a non-transfer position where the dark stripe ds is not secondarily transferred to the recording sheet P.

  Even if white stripes ws and dark stripes are in a position where they are reflected on the recording sheet P, if they are caused by defects in the color photosensitive development units (6Y, 6M, 6C). By doing the following, it becomes possible to avoid the occurrence of those streaks. That is, the color is changed to monochrome and output.

  Therefore, when the control unit 50 does not generate the periodic density abnormality on the intermediate transfer belt 8 and generates white stripes ws or dark stripes, that is, in the case of N in S6 of FIG. It is determined whether ws or dark stripe ds is reflected on the recording sheet P (S10). At this time, when white stripes ws and dark stripes ds are generated on the intermediate transfer belt 8 for each of a plurality of colors, it is determined whether or not each color is reflected on the recording sheet P.

  In this determination, it is assumed that the white streak ws or dark streak ds on the intermediate transfer belt 8 is not reflected on the recording sheet P for any color (N in S10). In this case, since no periodic density abnormality, white streaks, or dark streaks are generated on the recording sheet P, the control unit 50 advances the processing flow to S3 and starts print job processing.

  On the other hand, when the white streak ws or dark streak ds on the intermediate transfer belt 8 is reflected on the recording sheet P (Y in S10), the control unit 50 next determines whether or not the reflection occurs at K. (S11). If it does not occur in K (N in S11), it will occur in color (any of Y, M, or C), but if the output in color is stopped and output in monochrome, white streak ws or dark No streak ds is generated. Therefore, if the reflection of the white streak ws or the dark streak ds on the recording sheet P does not occur in K (N in S11), the control unit 50 asks the user whether or not the color image may be monochrome. Processing for inquiring is performed (S12). Specifically, as shown in FIG. 16, there is a high possibility that streaks are generated when output in the color mode, and inquiries about whether colors can be converted to monochrome so as not to cause streaks are described. The message is displayed on the display unit 65a. When the user who confirms the display presses the OK button displayed on the display unit and inputs information indicating permission (Y in S13 in FIG. 13), the original image received from a personal computer or the like is input. The information is subjected to monochrome processing to convert the color image information into monochrome image information (S14). Based on the monochrome image information, print job processing (S3 to S5) is performed.

  On the other hand, when information indicating that monochromeization is not permitted is input by the user (N in S13), the control unit 50 advances the processing flow to S7 described above to identify an abnormal image density location (periodic density error). A process for inquiring to the user whether or not it may be generated is performed (S7). In this inquiry, the inquiry screen shown in FIG. 17 is displayed on the display unit 65a instead of the inquiry screen shown in FIG. The inquiry screen in FIG. 14 is a message notifying that there is a high possibility of generating a shading pattern, whereas the inquiry screen in FIG. 17 is a message notifying that there is a high possibility of causing a streak. ing. When the user who confirms the screen display presses the OK button displayed on the display unit and inputs information indicating permission (Y in S8 in FIG. 13), the control unit 50 displays the above-described print. Perform job processing. On the other hand, when information indicating that permission is not permitted is input (N in S8), a message “print execution has been canceled” is displayed on the display unit 65a (S9), and then a series of processing flows is performed. Return to S1.

  In the above-described step of S11, when it is determined that the streak is reflected at K (Y at S11), the white streak ws and the dark streak are not eliminated even when the monochrome is performed. However, there are cases where such streaks can be eliminated by reduction as in the example of reduction from A3 size to B4 size and reduction from A4 size to B5 size shown in FIG. Therefore, the control unit 50 determines whether or not the streak is eliminated by the reduction (S15). If the problem is resolved (Y in S15), a process for inquiring the user whether or not the image may be reduced from the original is performed (S16). Specifically, as shown in FIG. 18, there is a high possibility that streaks are generated if the original size is maintained, and an inquiry item about whether the size can be reduced so as not to generate streaks is described. The message is displayed on the display unit 65a. It is assumed that information indicating permission is input by the user who has confirmed the display pressing the OK button displayed on the display unit (Y in S17 of FIG. 13). In this case, the original image information received from a personal computer or the like is reduced to convert the original page size to a slightly smaller page size (for example, A3 to B4) (S18). Based on the converted image information, print job processing (S3 to S5) is performed.

  On the other hand, when information indicating that the reduction is not permitted is input by the user (N in S17), the control unit 50 advances the processing flow to S7 described above and causes the display unit 65a to display the inquiry screen of FIG. . The subsequent processing is as described above.

  In such a process, after an image density abnormality portion such as a white streak ws occurs, when a print command is issued from the user at a timing before the inspection of the apparatus (Y in S1 of FIG. 13), a predetermined value is given. The condition determination process for determining whether or not the condition is satisfied is performed. When it is determined that the predetermined condition is satisfied in the condition determination process, a print job based on the print command is executed. In such a configuration, even when a streak-like abnormal density abnormal portion such as white stripe ws, dark stripe ds, periodic white spot, or excessive periodic density occurs, information indicating permission is received from the user (predetermined) If the above condition is satisfied, the print job is executed. Thereby, an image can be provided to a user who wants to provide an image after knowing the abnormality.

  Further, as a predetermined condition, when the condition that a stripe-like image density abnormal portion such as a white stripe ws on the surface of the intermediate transfer belt 8 occurs at a non-transfer position where the secondary transfer is not performed on the recording sheet P is satisfied (S10). In N), a print job is executed. With such a configuration, even if a streak-like image density abnormality portion occurs on the surface of the intermediate transfer belt 8, if the image density abnormality portion is not reflected on the recording sheet P, a print job is executed. Thereby, convenience can be improved by providing a user with an image without an image density abnormality location.

  The print job is also executed when the predetermined condition that information indicating that the execution of the print job based on the print command is permitted is input to the operation display unit 65 (Y in S8). . In such a configuration, even if an image density abnormal portion on a streak such as a white streak ws occurs, it is convenient for a user who allows it by executing a print job and providing an image. Can be increased.

  When an original color image is formed, streaky image density abnormal portions on the intermediate transfer belt 8 are generated. On the other hand, when a color image is converted into a monochrome image, the abnormal image density portions are not generated. Is inquired about conversion permission (S12). Then, when information indicating permission is input by the user in response to the inquiry (Y in S13), the print job is executed. In such a configuration, even for an image whose hue is changed from the original, an image whose hue is changed can be provided to a user who wishes to provide it, thereby improving convenience.

  Further, when image formation based on original image information is executed, streaky image density abnormal portions are generated on the recording sheet P. On the other hand, when the image is reduced and formed on a smaller size recording sheet P, the recording sheet P is subjected to the image formation. Assume that no image density abnormality occurs. Even in this case (Y in S15), after inquiring for permission to reduce the image (S16), if information indicating permission is input by the user in response to the inquiry (Y in S17), the print is also performed. Run the job. In such a configuration, even if the image is reduced in size from the original size, it is possible to provide the user who desires to provide the image with the reduced size, thereby improving convenience.

What was demonstrated above is an example, and there exists an effect peculiar for every following aspect.
[Aspect A]
Aspect A is an image forming means for forming a toner image (for example, a combination of the photosensitive developing units 6Y, 6M, C, and K and the optical writing unit 20) and a plurality of test toner images formed on the image forming means. The presence or absence of streaky image density abnormal portions (for example, white streak ws, dark streak ds) in the test toner image is determined based on the result of detecting the image density of the portion by the image density detecting means (for example, the image density sensor 18). And a control unit (for example, the control unit 50) that implements measures (for example, notification of the occurrence of white lines or dark lines) for preventing the formation of the image having the streaky image density abnormality portion based on the determination result. Each of the plurality of locations based on a detection result by the image density detection means for a plurality of locations of the first test toner image formed on the imaging means. The image forming condition (for example, optical writing intensity) of the image forming unit is corrected so as to suppress the image density deviation in the image, and the image forming unit forms a second test toner image under the corrected image forming condition. The control unit is configured to determine the presence or absence of a streak-like image density abnormality portion based on the detection result by the image density detection unit at a plurality of locations in the second test toner image. is there.

  In aspect A, prior to determining the presence or absence of streak-like image density abnormalities using the second test toner image as the test object, the presence or absence of image density deviation was detected at a plurality of locations in the first test toner image. Based on the result, the image forming conditions are adjusted so as to suppress the image density deviation. At this time, when the first test toner image has a streak-like image density defect that can be suppressed by adjusting the image-forming conditions, instead of a streak-like image density abnormality caused by an apparatus abnormality. The image forming conditions are corrected so as to suppress the image density defect. Thereafter, a second test toner image is formed under the corrected image forming conditions. Due to the correction of the immediately preceding image forming condition, the second test toner image has almost no streak-like image density defect that can be suppressed by adjusting the image forming condition. For this reason, in the second test toner image, a streak-like image density defect that can be suppressed by adjusting the image forming condition is rarely erroneously detected as a streak-like image density abnormality portion caused by an apparatus abnormality. Based on the result of detecting the image density of the second test toner image, by determining the presence / absence of an image density abnormality portion caused by an apparatus abnormality, a streak-like image density defect that can be suppressed by adjusting the image forming condition is eliminated. Suppressing false detection as an image density abnormality location due to device abnormality. As a result, it is possible to suppress unnecessary implementation of measures for preventing the formation of an image having a streak-like image density abnormality portion.

[Aspect B]
In the aspect B, in the aspect A, in correcting the image forming condition, an average value obtained by averaging the image densities at a plurality of portions of the first test toner image is calculated, and a difference from the calculation result exceeds a predetermined threshold value. Alternatively, the control means is configured to correct the image forming condition on the condition that an image density shift is suppressed only for an image portion that is equal to or greater than a threshold value. With such a configuration, it is possible to avoid complication of control due to dealing with inconspicuous level image density fluctuations.

[Aspect C]
Aspect C calculates the average value obtained by averaging the image densities at a plurality of locations of the second test toner image in determining whether or not there is a streak-like image density abnormality location in Aspect B, and the difference from the calculated result is The control means is configured to determine the presence / absence of a streak-like image density abnormality location based on the presence / absence of an image location that exceeds or exceeds the threshold value. In such a configuration, the presence or absence of a streak-like image density abnormality portion can be accurately determined by adopting the following condition as a determination criterion. That is, the difference from the average value of the image density in the first test toner image exceeds or exceeds the threshold value, and the difference from the average value of the image density in the second test toner image after correction of the image forming conditions is also the threshold value. It is a condition that exceeds or exceeds a threshold value.

[Aspect D]
Aspect D is that in the aspect B or C, the control means is configured to form the second test toner image having the same image density as the first test toner image previously formed. It is a feature. In such a configuration, it is possible to avoid deterioration in accuracy of determination of the presence / absence of an abnormal image density due to the image density of the second test toner image being different from that of the first test toner image.

[Aspect E]
Aspect E is an image forming apparatus according to aspect D, in which a high-density first test toner image having a relatively high image density and a low-density first test toner image having a lower image density are formed as the first test toner image. And determining whether or not there is an image density shift lower than usual for each of the plurality of locations based on a detection result by the image density detection unit for the high density first test toner image. The control unit is configured to determine whether or not there is an image density shift that is higher than normal at each of the plurality of locations based on a detection result of the image density detection unit for one test toner image. It is what. In such a configuration, as compared with the case where only one of the low-density first test toner image and the high-density first test toner image is formed as the first test toner image, a streak-like image density is insufficient and The occurrence of excessive image density can be accurately detected.

[Aspect F]
Aspect F is the aspect E, wherein the second test toner image is a high-density second test toner image having the same image density as the high-density first test toner image, and the same image density as the low-density first test toner image. A low-density second test toner image, and based on the detection result by the image density detection means for the high-density second test toner image, the image density is lower than usual at each of the plurality of locations. The image density is higher than usual for each of the plurality of locations based on the detection result by the image density detection means for the low density second test toner image. The control means is configured to determine whether or not there is a streak-like image density abnormality portion. In such a configuration, as the second test toner image, an image density abnormal portion where the image density is low is compared with a case where only one of the low density second test toner image and the high density second test toner image is formed. Presence / absence and presence / absence of an abnormal image density portion where the image density is high can be accurately determined.

[Aspect G]
Aspect G is the recording medium according to any one of Aspects A to F, wherein the first test toner image and the second test toner image formed by the image forming means are recorded from the surface of an image carrier (for example, intermediate transfer belt 8). The image density is provided so that a transfer means (for example, a transfer unit 7) for transferring to the sheet is provided and the image density of the first test toner image or the second test toner image on the surface of the image carrier is detected. The detection means is configured. In such a configuration, it is possible to detect the image density of the test toner image without transferring the first test toner image or the second test toner image to the recording sheet. The need for consumption can be eliminated, and wasteful resource consumption can be avoided.

[Aspect H]
In the aspect H, in the aspect G, the presence / absence of an abnormal image density portion extending in the surface movement direction (for example, the sub-scanning direction) on the surface of the image carrier is determined as the streaky image density abnormal portion. The control means is configured. With such a configuration, it is possible to quickly detect the occurrence of a streak-like image density abnormality portion extending in the surface movement direction.

[Aspect I]
In the aspect I, in the aspect H, the control unit is configured to determine whether or not there are abnormal image density portions periodically generated in the surface movement direction in addition to the streaky image density abnormal portions. It is characterized by this. With this configuration, it is possible to quickly detect the occurrence of an abnormal image density portion having periodicity in the surface movement direction.

[Aspect J]
Aspect J is aspect I, in which the image forming means is a latent image carrier (for example, photoconductors 1Y, 1M, 1C, and 1K), and a latent image forming means for forming a latent image on the surface thereof (for example, optical writing And a developing unit (for example, developing devices 5Y, 5M, 5C, and 5K) that develops the latent image with a developer carried on the surface of a developer carrying member (for example, a developing sleeve) to obtain a toner image. And the first test toner image or the second test toner image has a length in the surface movement direction of the latent image carrier, and a circumferential length in the surface movement direction of the latent image carrier, and It is characterized by being larger than any of the circumferential lengths in the direction of surface movement of the developer carrier. With this configuration, in the first test toner diagram and the second test toner image, it is possible to reliably detect image density defects that occur during the rotation cycle of the latent image carrier and image density defects that occur during the rotation cycle of the developer carrier. can do.

[Aspect K]
A mode K includes, in any of modes A to J, information notifying means (for example, an operation display unit 65) for notifying the user of information, and information for prompting the user to check the image forming apparatus. When a process informed by the means (for example, S18 in FIG. 11) is performed as the countermeasure, and an image formation command (for example, a print command) is issued from the user at a timing after the processing is performed and before the inspection is performed ( (For example, Y in S1 in FIG. 13), a condition determination process for determining whether or not a predetermined condition is satisfied (for example, a flow excluding S3 to S5 in FIG. 13) is performed, and the predetermined condition is determined in the condition determination process. The control means is configured to execute image formation based on the image formation command when it is determined that the above condition is satisfied. In such a configuration, even when a streak-like abnormal density abnormality portion occurs, when a predetermined condition is satisfied, for example, a forced operation command is issued from the user, an image forming operation is executed, Images can be provided to the user.

[Aspect L]
Aspect L is aspect K, wherein the image forming means forms a toner image on the surface of the image carrier, and a transfer means for transferring the toner image on the surface of the image carrier to a recording sheet. And the predetermined condition occurs at a non-transfer position as a surface position of the image carrier where the streaky image density abnormal portion on the surface of the image carrier is not transferred to a recording sheet. It is characterized by that. In such a configuration, even when a streak-like image density abnormality portion occurs on the surface of the image carrier, if the image density abnormality portion is not reflected on the recording sheet, an image forming operation is performed. Thus, it is possible to provide the user with an image having no image density abnormality portion. Thereby, the convenience can be improved.

[Aspect M]
Aspect M is L, and includes information input means (for example, operation display unit 65) for performing an information input operation by the user, and the predetermined condition permits execution of image formation based on the image formation command The information to the effect is input to the information input means. In such a configuration, even if an abnormal image density portion occurs, it is possible to improve convenience by providing an image by performing an image forming operation for a user who allows it.

[Aspect N]
Aspect N is aspect M, and the image forming means forms toner images of different colors on the surfaces of a plurality of latent image carriers (for example, photoreceptors 1Y, 1M, 1C, and 1K). When the control unit forms an image based on original image information (for example, the same image information sent from a personal computer or the like), the toner image of a predetermined color on the surface of the image carrier or the streaks around the toner image is formed. When an image is formed by replacing the predetermined color with another color while the image-shaped abnormal portion of image density is generated, the toner image of the other color on the surface of the image carrier or the streak-like image around it When the density abnormal portion does not occur, information for inquiring whether or not to allow the change from the predetermined color to the other color is notified by the information notification unit, and the predetermined condition is set. , After notification of the information is that information that is permitted is input to the information input unit, it is characterized in. In such a configuration, even for an image whose hue is changed from the original, an image whose hue is changed can be provided to a user who wishes to provide it, thereby improving convenience.

[Aspect O]
Aspect O is Aspect M or N, wherein the image forming means forms a toner image on the surface of the image carrier, and the toner image formed on the surface of the image carrier is recorded on the recording sheet. A transfer means for transferring the toner image, and the control means executes the image formation based on the original image information, while the toner image transferred to the recording sheet or the streaky image density abnormal portion is generated around the toner image. When the image is reduced from the original size and formed on a recording sheet having a smaller size than the original, the toner image transferred to the recording sheet having a smaller size or the streak-like image density abnormality portion does not occur around the toner image. Information for inquiring whether or not the image is to be formed smaller than the original is notified by the information notification means, and the predetermined condition is that the information indicating that the information is permitted after the notification of the information. It is input to the input means, it is characterized in. In such a configuration, even if the image is reduced in size from the original size, it is possible to provide the user who desires to provide the image with the reduced size, thereby improving convenience.

1Y, 1M, 1C, 1K: photoconductor (latent image carrier)
6Y, 6M, 6C, 6K: photosensitive developing unit (part of image forming means)
7: Transfer unit (transfer means)
8: Intermediate transfer belt (image carrier)
18: Image density sensor (image density detection means)
20: Optical writing unit (part of image forming means, latent image forming means)
50: Control unit (control means)
65: Operation display section (information notification means, information input means)
ws: White streak (striped image density abnormal portion with low image density)
ds: dark streak (striped image density abnormal portion having a high image density)
α: threshold value It ₁ : first test toner image It ₂ : second test toner image

JP 2014-134673 A

Claims (15)

Image forming means for forming a toner image, and a streak-like shape in the test toner image based on the result of image density detection means detecting the image density at a plurality of locations of the test toner image formed on the image forming means. In an image forming apparatus comprising: a control unit that determines presence / absence of an image density abnormality portion and implements measures for preventing the occurrence of the streaky image density abnormality portion based on a determination result;
Based on the detection result by the image density detection unit for a plurality of positions of the first test toner image formed on the image forming means, the image forming means creates the image so as to suppress the image density deviation at each of the plurality of positions. Based on the detection result by the image density detecting unit for a plurality of locations in the second test toner image, correcting the image condition, causing the image forming unit to form a second test toner image under the corrected image forming condition. An image forming apparatus comprising the control means so as to determine the presence or absence of a streak-like image density abnormality portion. The image forming apparatus according to claim 1.
In correcting the image forming conditions, an average value obtained by averaging the image densities of a plurality of portions of the first test toner image is calculated, and only an image portion whose difference from the calculation result exceeds a predetermined threshold or is equal to or more than the threshold. An image forming apparatus characterized in that the control means is configured to correct the image forming condition under the condition of suppressing an image density shift. The image forming apparatus according to claim 2.
In determining the presence / absence of a streak-like image density abnormality portion, an average value is calculated by averaging the image densities for a plurality of portions of the second test toner image, and a difference from the calculation result exceeds the threshold value or exceeds the threshold value. An image forming apparatus, wherein the control means is configured to determine the presence or absence of a streak-like image density abnormality portion based on the presence or absence of an image portion. The image forming apparatus according to claim 2 or 3,
An image forming apparatus, wherein the control unit is configured to form the second test toner image having the same image density as that of the first test toner image previously formed. The image forming apparatus according to claim 4.
As the first test toner image, a high density first test toner image having a relatively high image density and a low density first test toner image having a lower image density are formed, and the high density first test toner is formed. The image of the low-density first test toner image is determined based on the detection result of the image density detection unit for the image while determining whether there is an image density shift that is lower than usual for each of the plurality of locations. An image forming apparatus, wherein the control unit is configured to determine the presence or absence of an image density shift that is higher than normal at each of the plurality of locations based on a detection result by the density detection unit. The image forming apparatus according to claim 5.
As the second test toner image, a high density second test toner image having the same image density as the high density first test toner image, and a low density second test toner image having the same image density as the low density first test toner image. And a streak-like image density abnormal portion where the image density is lower than usual for each of the plurality of locations based on the detection result by the image density detection means for the high-density second test toner image A streak-shaped image density abnormality portion in which the image density is higher than usual in each of the plurality of locations based on the detection result by the image density detection unit for the low-density second test toner image An image forming apparatus characterized in that the control means is configured to determine the presence or absence. The image forming apparatus according to any one of claims 1 to 6,
A transfer means for transferring the first test toner image or the second test toner image formed by the image forming means from the surface of the image carrier to a recording sheet;
An image forming apparatus comprising: the image density detecting unit configured to detect an image density of the first test toner image or the second test toner image on the surface of the image carrier. The image forming apparatus according to claim 7.
The image forming apparatus is characterized in that the control means is configured to determine whether or not the streaky image density abnormality portion is an image density abnormality portion extending in a surface movement direction on the surface of the image carrier. apparatus. The image forming apparatus according to claim 8.
In addition to the streak-like image density abnormality location, the control means is configured to determine whether or not there is a periodic density abnormality location that is an image density abnormality location that periodically occurs in the surface movement direction. An image forming apparatus. The image forming apparatus according to claim 9, wherein
Development in which the image forming means develops the latent image with a latent image carrier, a latent image forming means for forming a latent image on the surface thereof, and a developer carried on the surface of the developer carrier to obtain a toner image. Having means,
In addition, as the first test toner image and the second test toner image, the length of the latent image carrier in the surface movement direction is the circumferential length of the latent image carrier in the surface movement direction, and the developer carrier. An image forming apparatus characterized by being larger than any of the circumferential lengths in the surface movement direction. The image forming apparatus according to any one of claims 1 to 10,
Providing information notifying means for notifying the user of information;
A process for notifying the user of information for inspecting the image forming apparatus by the information notification means is implemented as the countermeasure, and an image forming instruction is issued from the user at a timing after the process and before the inspection is performed. If the condition determination process determines that the predetermined condition is satisfied, the image formation based on the image formation command is executed. Thus, an image forming apparatus comprising the control means. The image forming apparatus according to claim 11, comprising:
The image forming means is for forming a toner image on the surface of the image carrier,
Transfer means for transferring the toner image on the surface of the image carrier to a recording sheet is provided,
Further, the predetermined condition is that the streaky image density abnormal portion on the surface of the image carrier is generated at a non-transfer position as a surface position of the image carrier that is not transferred to a recording sheet. An image forming apparatus. The image forming apparatus according to claim 12, wherein
An information input means for performing information input operation by the user is provided,
In addition, the predetermined condition is that information indicating that execution of image formation based on the image formation command is permitted is input to the information input unit. The image forming apparatus according to claim 13,
The image forming means forms toner images of different colors on the surfaces of a plurality of latent image carriers,
When the control unit forms an image based on the original image information, the toner image of the predetermined color on the surface of the image carrier or the streaky image density abnormal portion is generated around the toner image, while the predetermined color is changed. When an image is formed instead of another color, when the toner image of the other color on the surface of the image carrier or the streaky image density abnormal portion does not occur around the toner image, the other color is changed from the predetermined color to the other color. Information for inquiring whether or not to permit change to the color is notified by the information notification means,
The predetermined condition is that information indicating permission is input to the information input unit after the information is notified. The image forming apparatus according to claim 13 or 14,
The image forming means is for forming a toner image on the surface of the image carrier,
Transfer means for transferring the toner image formed on the surface of the image carrier to a recording sheet is provided,
When the image forming based on the original image information is executed, the control means generates the streaky image density abnormal portion on the toner image transferred to the recording sheet or the periphery thereof, while reducing the image from the original size. If the image is formed on a recording sheet having a size smaller than the original, and the toner image transferred to the recording sheet having a smaller size or the streaky image density abnormal portion does not occur around the toner image, the image is reduced and formed. Information for inquiring whether or not is notified by the information notification means,
The predetermined condition is that information indicating permission is input to the information input unit after the information is notified.