JP2011008030A - Image forming apparatus and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus and program which suppress fluctuations of the density of the first image while improving productivity per unit time of the first image.SOLUTION: A print image is formed by one image on a periphery surface of a photoreceptor drum 30 while shifting a formation position in a rotation direction, while a reference image is formed on at least either a front side or a rear side of the rotation direction of the print image, and the density of the reference image is detected by a density sensor 44. When the position where the reference image the density of which is detected is formed is not a predetermined position on the periphery surface of the photoreceptor drum 30, the degree of correction is decreased compared with the case that the position is the predetermined position, and the density of the print image formed by an image forming part is corrected based on the density of the reference image.

Description

  The present invention relates to an image forming apparatus and a program.

  In Patent Document 1, an image formed on a latent image carrier in an image forming apparatus that forms an electrostatic latent image on the latent image carrier and visualizes the electrostatic latent image with a developer containing at least toner. An image forming apparatus is described that includes an optical sensor that detects visible image information relating to an image, and the optical sensor detects visible image information at a constant position on the latent image carrier.

  In Patent Document 2, a latent image formed on a photoreceptor is used in an image forming apparatus that visualizes a latent image using toner, and the toner density when the latent image is visualized is kept constant. A toner density control method for detecting a reflectance of the surface of the photosensitive member before visualizing the latent image, and analyzing a period of unevenness of the reflectance of the surface of the photosensitive member from the detection result, A period that is not synchronized with the analyzed unevenness period is determined as a sampling interval, and the density of the toner patch image formed on the photoconductor is detected at the determined sampling interval, and the latent image is determined based on the detected density of the toner patch image. A toner density control method for correcting the density of toner when an image is visualized is described.

  In Patent Document 3, an electrostatic latent image is formed on the surface and an endlessly moving image carrier, and toner is attached to the electrostatic latent image at a development position facing the image carrier via a predetermined gap. A density detecting unit configured to detect a density of a reference image formed on the image carrier on the downstream side of the development position in the image carrier movement direction; Storage means for storing eccentricity data at each phase of the image carrier based on the home position on the image carrier, and home position detection means for detecting the phase of the reference image based on the home position. An image forming apparatus that corrects the density of the reference image detected by the density detection unit based on the eccentricity data in the phase where the reference image is formed is described.

Japanese Patent Laid-Open No. 08-76530 Japanese Patent Laid-Open No. 10-171236 Japanese Patent No. 2957859

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus and a program that can suppress the variation in the density of the first image while improving the productivity of the first image per unit time.

  According to a first aspect of the present invention, there is provided an image forming apparatus which rotates and holds an image formed on a peripheral surface, and a first position while shifting a forming position on the peripheral surface of the image holding body in the rotation direction. Image forming means for forming one image at a time and forming a second image on at least one of the front side and the rear side in the rotation direction of the first image; and a detection means for detecting the density of the second image; When the position where the second image whose density is detected by the detecting means is not a predetermined position on the peripheral surface of the image carrier, the correction is made as compared with the predetermined position. Correction means for reducing the degree and correcting the density of the first image formed by the image forming means based on the density of the second image detected by the detection means.

  According to a second aspect of the present invention, in the first aspect of the present invention, when the image forming unit is configured such that the inter-image portion of the first image is at the predetermined position on the peripheral surface. The second image is formed in the intermediate portion.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the image forming means receives the operation designation of an image quality priority operation that prioritizes the image quality of the image. When the operation designation in the image quality priority operation is accepted, the image interval for forming the first image is changed to be longer and the rotation of the image carrier is smaller than in the case where the operation designation in the image quality priority operation is not accepted. The second image is formed at the predetermined position on the peripheral surface by the number of times.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the image forming unit accepts an operation designation of a speed priority operation that prioritizes the speed of image formation. When the operation designation in the speed priority operation is received by the priority operation accepting unit, the frequency of forming the second image is reduced and at least one is compared with the case where the operation designation in the speed priority operation is not accepted. The first image is formed by changing the image interval at which the first image is formed at a short portion.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the detection means detects and averages the density at a plurality of positions of the second image. Thus, the density of the second image is detected, and when the image forming unit forms the second image at a position other than the predetermined position, the density is compared with the case where the second image is formed at the predetermined position. The second image is formed long in the direction in which the detection position of the density of the second image by the detecting means increases.

  According to a sixth aspect of the present invention, there is provided the invention according to any one of the first to fifth aspects, wherein the circumference of the image carrier is different for each length of the recording medium with respect to the circumferential direction of the image carrier. Storage means for storing interval information relating to the interval at which the first image is formed on the surface, wherein the first image formed on the peripheral surface of the image carrier is directly or intermediately transferred. The first image is formed at intervals based on the interval information corresponding to the length of the recording medium transferred via the circumferential direction.

  On the other hand, the program of the invention described in claim 7 rotates the computer and shifts the first image 1 while shifting the formation position in the rotation direction on the peripheral surface of the image holding member that holds the image formed on the peripheral surface. An image forming unit that forms each of the first images and forms a second image on at least one of the front side and the rear side of the rotation direction of at least a part of the first image; and a detection unit that detects the density of the second image When the position where the second image where the density is detected is not a predetermined position on the peripheral surface of the image carrier, the degree of correction is reduced as compared with the case where the second image is the predetermined position. And a correction unit that corrects the density of the first image formed by the image forming unit based on the density of the second image detected by the detection unit.

  According to the first and seventh aspects of the invention, the first image per unit time is compared with the case where the first images are formed one by one on the peripheral surface of the image carrier without changing the formation position. Variation in the density of the first image can be suppressed while improving the productivity of the image.

  According to the second aspect of the present invention, fluctuations in the density of the first image can be suppressed as compared to the case where the second image is not formed in the inter-image portion of the first image.

  According to the third aspect of the present invention, the variation in the density of the first image can be suppressed as compared with the case where the image quality priority operation is not designated.

  According to the fourth aspect of the present invention, the speed of image formation per unit time is improved as compared with the case where the speed priority operation is not designated.

  According to the invention described in claim 5, when the second image is formed at a position other than the predetermined position, a part of the second image is compared with the case where the second image is not formed long. Even when the density suddenly changes in the area, the fluctuation of the density of the first image can be suppressed.

  According to the invention described in claim 6, compared to the case where the interval for forming the first image is not stored for each length of the recording medium with respect to the circumferential direction of the image carrier, and the interval is constant, For each length of the recording medium with respect to the circumferential direction of the image carrier, the period at which the inter-image portion of the first image is a predetermined position is changed.

1 is a plan view illustrating a schematic configuration of an image forming apparatus according to an embodiment. It is a top view which shows schematic structure inside the apparatus main body which concerns on embodiment. FIG. 2 is an enlarged perspective view illustrating a configuration of a photosensitive drum according to an embodiment. 1 is a block diagram illustrating a configuration of a main part of an electric system of an image forming apparatus according to an embodiment. It is a figure which shows an example of the data structure of the space | interval information according to paper which concerns on embodiment. It is a top view which shows an example of the reference | standard image which concerns on embodiment. 4 is a flowchart showing a flow of processing of an image forming processing program according to the first embodiment. FIG. 5 is a diagram illustrating an example of each image transferred to an intermediate transfer belt when an image is formed on an A4 size (SEF) sheet by image forming processing according to the first embodiment. FIG. 7 is a diagram illustrating an example of each image transferred to an intermediate transfer belt when an image is formed on an irregular large size sheet by the image forming process according to the first embodiment. It is a flowchart which shows the flow of a process of the density | concentration correction process program which concerns on 1st Embodiment. FIG. 10 is a diagram illustrating an example of each image transferred to an intermediate transfer belt when an image is formed on an A4 size (SEF) sheet by image forming processing according to the second embodiment. It is a flowchart which shows the flow of a process of the density | concentration correction process program which concerns on 2nd Embodiment. 14 is a flowchart illustrating a flow of processing of an image forming processing program according to a third embodiment. FIG. 10 is a diagram illustrating an example of each image transferred to an intermediate transfer belt when an image is formed on an A4 size (SEF) sheet by an image quality priority operation by an image forming process according to a third embodiment. FIG. 10 is a diagram illustrating an example of each image transferred to an intermediate transfer belt when an image is formed on an A4 size (SEF) sheet by speed priority operation by an image forming process according to a third embodiment. FIG. 10 is a diagram illustrating an example of each image transferred to an intermediate transfer belt when an image is formed on an A4 size (SEF) sheet by image forming processing according to another embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the following, an embodiment in which the present invention is applied to an image forming apparatus having a copy function and a print (print) function will be described.

[First Embodiment]
FIG. 1 shows a schematic configuration of an image forming apparatus 10 according to the present embodiment.

  The image forming apparatus 10 reads an image from a document placed at a reading position, acquires image information indicating the image, and image information acquired by the scanner 12, or based on image information acquired from the outside. An image is formed on the apparatus main body 14 that performs the forming process, a touch panel display (hereinafter referred to as “display”) 16 that displays an operation menu, a message, and the like and that is integrally provided with a transmissive touch panel on the surface. And a plurality of paper feed trays 20 in which the paper P before image formation is stored. The paper discharge tray 18 holds paper P (see also FIG. 2) discharged from the apparatus main body 14. In the present embodiment, the paper P corresponds to an example of a recording medium.

  Each paper feed tray 20 has a variable size of the paper P to be accommodated by adjusting the position of an internal partition member or the like. Each paper feed tray 20 accommodates a plurality of sheets P stacked.

  Note that the image forming apparatus 10 according to the present embodiment employs a pressure-sensitive touch panel as the touch panel, and forms an image when the user touches the display surface of the display 16 with a fingertip (touch operation). Various operations are instructed to the apparatus 10.

  Next, a schematic configuration inside the apparatus main body 14 will be described with reference to FIG.

  The apparatus main body 14 according to the present embodiment includes an image forming engine unit 22 that forms an image on a sheet P by an electrophotographic method.

  The image forming engine unit 22 according to the present embodiment includes four image forming units 24Y, 24M, 24C, and 24K. The image forming units 24 are arranged at predetermined intervals along the longitudinal direction of the intermediate transfer belt 26. The intermediate transfer body belt 26 is stretched around a plurality of winding rollers 28 and a roller 46A of a second transfer unit 46 described later, and is formed in an endless belt shape that is conveyed in the direction of arrow E in FIG.

  The image forming unit 24Y corresponds to yellow (Y), the image forming unit 24M corresponds to magenta (M), the image forming unit 24C corresponds to cyan (C), and the image forming unit 24K corresponds to black (K). An image of each corresponding color is formed. In FIG. 2, an alphabet (Y / M / C / K) indicating a color corresponding to the end of the code is given, but in the following, this alphabet at the end of the code is omitted unless the color is particularly distinguished. I will explain.

  The image forming unit 24 is provided with a cylindrical photosensitive drum 30 that is rotationally driven at a predetermined rotational speed in the direction of arrow F in FIG. In the present embodiment, the photosensitive drum 30 corresponds to an example of an image carrier. As shown in FIG. 3, a disk member 32 having a notch 32 </ b> A on the rotation shaft is provided on the side surface of each photosensitive drum 30. The image forming unit 24 is provided with a sensor 34 for detecting the cutout portion 32 </ b> A of the disk member 32, and a rotary encoder (not shown) is provided on the rotating shaft of the photosensitive drum 30. Thus, the sensor 34 detects the position of the cutout portion 32A of the disk member 32, thereby determining whether the rotational position of the photosensitive drum 30 is a specific rotational position. Further, by counting the number of pulses of the pulse signal output from the rotary encoder from the time when the notch 32A is detected, the rotational position of the photosensitive drum 30 is obtained, and the unit time of the pulse signal output from the rotary encoder is determined. The rotational speed of the photosensitive drum 30 is obtained based on the number of pulses or the pulse width of the pulse signal. In the image forming apparatus 10 according to the present embodiment, the rotational position of the photosensitive drum 30 where the notch 32A is detected by the sensor 34 is set as the initial position, and each photosensitive drum 30 is moved when image formation is started. After aligning the rotational position with the initial position, rotational driving at a predetermined rotational speed is started.

  As shown in FIG. 2, a charger 36 that uniformly charges the surface of the photosensitive drum 30 is disposed around each photosensitive drum 30. Charging of the photosensitive drum 30 by the charger 36 is the first stage of a series of image forming processes. Further, a light beam based on a desired image is irradiated on the downstream side of the charger 36 along the rotation direction of each photosensitive drum 30 in the axial direction of the photosensitive drum 30 uniformly charged by the charger 36. An optical scanning device 38 for forming an electrostatic latent image is disposed on the photosensitive drum 30.

  Further, there are colors around the photosensitive drums 30 that are respectively responsible for the electrostatic latent images formed on the photosensitive drums 30 on the downstream side of the optical scanning device 38 along the rotation direction of the photosensitive drums 30. A developing device 40 is provided that develops each color image by developing with (yellow / magenta / cyan / black) toner. A contact point with the intermediate transfer belt 26 is located downstream of the developing unit 40, and a first transfer unit 42 is disposed. The first transfer device 42 is applied with a predetermined voltage to transfer the image on the photosensitive drum 30 to the intermediate transfer belt 26.

  Images of different colors formed on the respective photosensitive drums 30 are transferred onto the intermediate transfer belt 26 so as to overlap each other on the belt surface of the intermediate transfer belt 26 (in the same region). As a result, a color image is formed on the intermediate transfer belt 26.

  A density sensor 44 for detecting the density of the image is provided on the downstream side in the transport direction (the direction of arrow E in FIG. 2) from the transfer position of the image on the intermediate transfer belt 26 by the photosensitive drum 30K. In the present embodiment, the density sensor 44 corresponds to an example of a detection unit.

  A second transfer unit 46 including a pair of rollers 46A and 46B is disposed on the downstream side of the intermediate transfer belt 26 with respect to the density sensor 44 in the transport direction.

  The paper P stored in the paper feed tray 20 (see FIG. 1) is fed out one by one by the paper feed unit 48. The fed paper P is once conveyed to the alignment roll 52 via the paper conveyance path 50 and stopped, and the second transfer device is synchronized with the color image on the intermediate transfer belt 26 by the alignment roll 52. The second transfer unit 46 transfers the color image on the intermediate transfer belt 26 onto the paper P in a batch (secondary transfer). The sheet P on which the color image has been transferred is conveyed to a fixing device 54 where the image is fixed (heating, pressing, etc.). As a result, the image is fixed on the paper P, and a desired image is formed on the paper P. The paper P on which the image is formed is discharged to the discharge tray 18 via the discharge roll 56.

  Each photosensitive drum 30 is prepared for the next image forming process by removing residual toner and the like by the cleaning device 60 after the image transfer process is completed. In addition, residual toner, paper dust, and the like are removed from the intermediate transfer belt 26 by a belt cleaner 62 disposed downstream of the second transfer unit 46.

  Next, with reference to FIG. 4, the main configuration of the electrical system of the image forming apparatus 10 according to the present embodiment will be described.

  The image forming apparatus 10 includes a CPU (Central Processing Unit) 100 that controls the operation of the entire apparatus, and a ROM (Read Only) as a storage medium in which various programs including an image forming processing program and a density correction processing program described later are stored in advance. Memory) 102, RAM (Random Access Memory) 104 for temporarily storing various data, non-volatile memory 106 for storing various information including sheet-by-sheet interval information described later, and display of various information on the display 16 A display control unit 108 that controls the operation, an operation input detection unit 110 that detects a touch operation on the display 16, and a network NET that transmits and receives information to and from an external terminal device (for example, a personal computer). A communication I / F unit 112 is provided.

  In addition, the image forming apparatus 10 controls the image forming control unit 114 that controls the image forming process performed by the image forming engine unit 22 described above, the sheet feeding unit 48, the alignment roll 52, and the discharge roll 56 to convey the sheet P. A conveyance control unit 116 for controlling the operation.

  The CPU 100, the ROM 102, the RAM 104, the nonvolatile memory 106, the display control unit 108, the operation input detection unit 110, the communication I / F unit 112, the image formation control unit 114, and the conveyance control unit 116 are mutually connected via the system bus BUS. It is connected. Therefore, the CPU 100 controls access to the ROM 102, RAM 104, and nonvolatile memory 106, displays various information such as operation screens and various messages on the display 16 via the display control unit 108, and a communication I / F unit. Control of transmission / reception of information to / from an external terminal device via 112, control of operation of the image formation engine unit 22 via the image formation control unit 114, and control of conveyance of the paper P via the conveyance control unit 116. Do each.

  Further, the CPU 100 grasps the operation content for the display 16 based on the operation information detected by the operation input detection unit 110, and the operation state of the image formation engine unit 22 based on various information derived by the image formation control unit 114. To figure out.

  Further, a density sensor 44 is further connected to the system bus BUS. Therefore, the CPU 100 grasps the density of the image detected by the density sensor 44.

  The image forming control unit 114 controls each image forming unit 24 (24Y, 24M, 24C, 24K) to form an image. Further, the image formation control unit 114 counts the number of pulses of the pulse signal output from the rotary encoder from the time point when the sensor 34 detects the notch 32A for each photoconductive drum 30 to thereby detect each photoconductive drum 30. 30 rotational positions are grasped. In the present embodiment, the charger 36, the optical scanning device 38, the developing device 40, and the image formation control unit 114 correspond to an example of an image forming unit.

  Next, density correction of the image forming apparatus 10 according to the present embodiment will be described.

  The non-volatile memory 106 stores a lookup table for each color of YMCK in order to adjust the image density.

  When the image information to be printed is input, the image forming apparatus 10 obtains an image of each color of YMCK from the image information to be printed based on a lookup table for each color of YMCK stored in the nonvolatile memory 106. Data is generated, and based on the generated image data of each color of YMCK, a print image as a first image is formed on the peripheral surface of each photosensitive drum 30 at an image interval corresponding to the length of the paper P. Further, the image forming apparatus 10 forms a reference image for density correction as a second image on the front side in the rotation direction of the print image formed on any one of the photosensitive drums 30. In this embodiment, one reference image is formed on the front side in the rotation direction of each print image, the color of the reference image is YMCK, and the density is Cin = 60% or Cin = 20%. As described above, the color and density of the reference image formed on the front side in the rotation direction of the print image are changed in a predetermined order.

  Further, the image forming apparatus 10 forms a rectangular toner band together with the reference image as necessary. This toner band adjusts the toner density in the developing device 40 of each image forming unit 24 or supplies the toner to the cleaning device 60 of each image forming unit 24 to cause excessive wear of a blade (not shown) of the cleaning device 60. In order to avoid the above, it is formed as necessary.

  The reference image, the print image, and the toner band formed on each photosensitive drum 30 are transferred to the intermediate transfer belt 26.

  In the present embodiment, the density sensor 44 detects the density of the reference image, and corrects the look-up table for each color of YMCK stored in the nonvolatile memory 106 based on the detected density of the reference image. Perform density feedback control.

  Furthermore, the image forming apparatus 10 according to the present embodiment is configured to continuously form the print image on the circumferential surface of the photosensitive drum 30 according to the length of the paper P with respect to the circumferential direction of the photosensitive drum 30. The sheet-by-sheet interval information regarding the interval is stored in the nonvolatile memory 106.

  FIG. 5 shows an example of the data structure of the interval information for each sheet when the length of the peripheral surface of the photosensitive drum 30 is 264 mm, for example.

  The sheet-by-sheet interval information includes the number of rotations for rotating the photosensitive drum 30 when a set of a print image, a reference image, and a toner band is formed according to the length of the sheet P with respect to the circumferential direction of the photosensitive drum 30. The maximum length and the minimum length in the circumferential direction of the reference image area are stored. The number of rotations when forming one set of the print image, the reference image, and the toner band increases as the length of the sheet P in the circumferential direction of the photosensitive drum 30 increases.

  Here, in the present embodiment, the reference image has a planar rectangular shape as shown in FIG. 6, and the reference image transferred to the intermediate transfer belt 26 and conveyed is detected by the density sensor 44 with a diameter of about 3 mm. By sampling the density of the region at a predetermined number (for example, 10 points) at a predetermined time interval ΔT, adding the density value of each detection point, and performing an averaging process that divides by the number of detection points The density of the reference image is detected. For this reason, the reference image needs to have a certain length along the moving direction of the intermediate transfer belt 26.

  On the other hand, in the present embodiment, the polarity and voltage value of the voltage applied to the second transfer device 46 when the reference image transferred onto the intermediate transfer belt 26 passes through the second transfer device 46 are switched. Then, the reference image and the toner band are passed through the secondary transfer position without being transferred by the second transfer unit 46, and removed from the intermediate transfer body belt 26 by the belt cleaner 62. For this reason, when the reference image and the toner band pass through the secondary transfer position, it is necessary to consider the time required for switching the polarity of the voltage applied to the second transfer unit 46 and the voltage value.

  In the sheet-by-sheet interval information according to the present embodiment, the length required for sampling a predetermined number (for example, 10 points) at a predetermined time interval ΔT by the density sensor 44 is stored as the minimum length. Between the reference image and the toner band and the print image, the length that ensures the voltage switching time of the second transfer unit 46 is stored as the maximum length.

  In the present embodiment, the reference image and the toner band are formed by the minimum length for each rotation number corresponding to the length of the paper P in the range of Min to Max.

  Next, the operation of the image forming apparatus 10 according to the present embodiment will be described.

  When copying with the image forming apparatus 10, the user places an original at the reading position of the scanner 12, specifies the paper size and the number of sheets on the operation screen displayed on the display 16, and then touches to instruct the start of copying. Perform the operation. In addition, when printing with the image forming apparatus 10, the user designates the paper size and the number of sheets on the external terminal device and instructs printing of the image information. The image information instructed to be printed is transmitted to the image forming apparatus 10 through the network NET together with information specifying the paper size and the number of sheets.

  When an operation to instruct the display 16 to start copying is performed, the image forming apparatus 10 reads a document with the scanner 12 and stores image information indicating the read image in the RAM 104. Further, when image information is received via the network NET, the image forming apparatus 10 stores the image information in the RAM 104.

  When the image information is stored in the RAM 104, the image forming apparatus 10 executes an image forming process by the CPU 100.

  FIG. 7 shows a flowchart showing the flow of processing of the image forming processing program executed by the CPU 100. The program is stored in advance in a ROM 102 as a recording medium.

  In step 200, based on the sheet-by-sheet interval information stored in the nonvolatile memory 106, the number of rotations in which the length of the designated sheet P in the circumferential direction of the photosensitive drum 30 falls within the range of Min to Max, and the reference image Find the length of the working area.

  In the next step 204, YMCK color image data is generated from the image information based on the lookup table for each color stored in the nonvolatile memory 106.

  In the next step 206, the conveyance control unit 116 is controlled to cause the image forming engine unit 22 to convey the sheet P having a size designated by the user.

  In the next step 208, the number of rotations obtained in step 200 and the length of the reference image area are output as image interval information to the image formation control unit 114 together with the YMCK color image data generated in step 204.

  When the image interval information and the YMCK color image data are input, the image formation control unit 114 controls each image forming unit 24 based on the input image interval information and the YMCK color image data, and the image interval information. One print image is formed on the peripheral surface of each photoconductive drum 30 at every rotation indicated by. The image formation control unit 114 forms the reference image on the front side in the rotation direction of the print image by changing the color and density in the predetermined order by the length of the reference image area indicated by the image interval information. Further, if necessary, a toner band is formed.

  The reference image, the print image, and the toner band formed on each photosensitive drum 30 are transferred to the intermediate transfer belt 26. The print image transferred to the intermediate transfer belt 26 is sent to the pressure contact position of the second transfer device 46 by driving the intermediate transfer belt 26, and is collectively transferred to the paper P by the second transfer device 46. In this embodiment, when the reference image and the toner band pass through the second transfer unit 46, the reference image and the toner band are switched by switching to the polarity and voltage value of the voltage applied to the second transfer unit 46. Is prevented from being transferred by the second transfer unit 46. The reference image and the toner band that have passed through the second transfer unit 46 are removed by the belt cleaner 62.

  In the next step 210, it is determined whether or not printing of the designated number of prints has been completed. If the determination is negative, the process proceeds to step 204. If the determination is affirmative, the process ends.

  FIG. 8 shows an example of each image transferred to the intermediate transfer belt 26 when an image is formed on, for example, A4 size (SEF) paper P. FIG. An example of each image transferred to the intermediate transfer belt 26 when an image is formed on a paper P having an irregular large size (482.7 mm to 488 mm) is shown. The drum N circumference described in FIGS. 8 and 9 and FIGS. 11, 14, 15, and 16 described later indicates the number of times the photosensitive drum 30 is N times during image formation. Indicates that the print image, the reference image, and the toner band correspond to the Nth sheet P.

  As shown in FIG. 8, on the SEF paper P, a set of a print image, a reference image, and a toner band is formed every time the photosensitive drum 30 rotates 1.50, and 16 sheets when the photosensitive drum 30 rotates 24 times. An image is formed on the paper P.

  On the other hand, as shown in FIG. 9, with a paper P of 482.7 mm to 488 mm, a set of a print image, a reference image, and a toner band is formed every time the photosensitive drum 30 rotates 2.50. Is rotated 40 times, an image is formed on 16 sheets of paper P.

  In the present embodiment, the cycle of forming one reference image having a density Cin = 60% and a density Cin = 20% for each color in the order of YMCK colors is repeated, and the density Cin = 10 for each color. The order of forming the reference image of 60% and density Cin = 20% is changed.

  By the way, the position of density detection of the intermediate transfer belt 26 by the density sensor 44 is fixed. Therefore, the timing at which the reference image formed on each photoconductor drum 30 reaches the density sensor 44 is determined. The image formation control unit 114 according to the present embodiment derives the detection timing at which the formed reference image reaches the density sensor 44 and is detected by the density sensor 44 when the reference image is formed. Further, the image formation control unit 114 determines the rotation position of the photosensitive drum 30 on which the reference image is formed from the rotation position of the photosensitive drum 30 when the light beam is irradiated from the optical scanning device 38 to form the reference image. To derive.

  The CPU 100 performs density correction processing at the detection timing derived by the image formation control unit 114.

  FIG. 10 shows a flowchart showing the flow of processing of the density correction processing program executed by the CPU 100. Note that the program is stored in the ROM 102 in advance.

  In step 252, the density sensor 44 is controlled, and the density of the reference image transferred to the intermediate transfer belt 26 is sampled at a predetermined number (for example, 10 points) at a predetermined time interval ΔT, and an averaging process is performed. By doing so, the density of the reference image is detected.

  In the next step 254, a density difference between the detected density of the reference image and the original density of the reference image is derived.

  In the next step 256, it is determined whether or not the reference image whose density has been detected is formed at a predetermined position on the peripheral surface of the photosensitive drum 30, and if the determination is affirmative, the process proceeds to step 258. If the determination is negative, the process proceeds to step 260. In the present embodiment, a predetermined position is a position where the first reference image is formed when the image is formed. In the image forming apparatus 10 according to the present embodiment, when image formation is started, rotation driving is started after the rotation positions of the respective photosensitive drums 30 are aligned with the initial positions. In accordance with the length of the paper P with respect to the direction, the number of rotations for rotating the photosensitive drum 30 when a set of the print image, the reference image, and the toner band is formed is determined. Periodically formed.

  In FIGS. 8, 9, and FIGS. 11, 14, 15, and 16, which will be described later, a reference image S is given to a reference image formed at a predetermined position on the peripheral surface of the photosensitive drum 30.

  As shown in FIGS. 8 and 9, the position for forming the reference image having the YMCK color density Cin = 60% is determined in advance for the first 8 sheets of paper P, and the subsequent 8 sheets of paper P are printed in the YMCK color. The position where the reference image with the density Cin = 20% is formed is a predetermined position.

  In step 258, if the density of the reference image is lower than the original density, the density is increased by the density difference derived in step 254. If the density of the reference image is higher than the original density, the density difference is increased by the density difference. The value of the lookup table is corrected so as to decrease, and the process is terminated.

  On the other hand, in step 260, if the density of the reference image is lower than the original density, the density is increased by a predetermined ratio (for example, 50%) of the density difference derived in step 254, and the density of the reference image is increased. When the density is higher than the original density, the value in the lookup table is corrected so as to reduce the density by a predetermined ratio of the density difference, and the process is terminated. In the present embodiment, the processing from step 256 to step 260 of the density correction processing program corresponds to an example of a correction unit.

  That is, when the reference image is formed at a predetermined position on the peripheral surface of the photosensitive drum 30, all the density differences between the density of the reference image and the original density of the reference image are corrected. On the other hand, if the reference image is not formed at a predetermined position on the circumferential surface of the photoconductive drum 30, the correction degree is decreased to determine a predetermined density difference between the density of the reference image and the original density of the reference image. The amount of light is corrected by the proportion.

  Here, the photosensitive characteristics of the photosensitive drum 30 are not necessarily uniform, and even if an attempt is made to form a reference image with the same density, the density of the reference image varies depending on the position in the circumferential direction due to variations in the photosensitive characteristics. That is, when the density of the reference image is simply detected and the image density is corrected, the density of the print image changes depending on the position where the reference image is formed.

Therefore, when the formation position of the reference image is not a predetermined position on the peripheral surface of the photosensitive drum 30, the density is corrected by reducing the correction degree as compared with the case where the reference image is formed at a predetermined position. The change in the density of the printed image can be suppressed as compared with the case where the density of the reference image is detected and the density is corrected without changing the correction degree regardless of the position where the reference image is formed. The ratio for reducing the correction degree may be determined in advance by an experiment using an actual machine, a computer simulation based on the design specifications of the image forming apparatus 10, or the like.
[Second Embodiment]
Since the schematic configuration of the image forming apparatus 10 according to the second embodiment, the schematic configuration inside the apparatus main body 14, and the main configuration of the electrical system are the same as those in the first embodiment, description thereof is omitted here. .

  When image interval information and YMCK color image data are input, the image formation control unit 114 according to the second embodiment receives each image forming unit 24 based on the input image interval information and YMCK color image data. Are controlled to form one print image on the peripheral surface of each photoconductive drum 30 for each number of rotations indicated by the image interval information. Further, the image formation control unit 114 rotates the photosensitive drum 30 that is to form the reference image from the rotational position of the photosensitive drum 30 when the light beam is irradiated from the optical scanning device 38 to form the reference image. The position is derived, and when the derived rotational position is other than a predetermined position on the peripheral surface of the photosensitive drum 30, the reference image is formed to be longer in the circumferential direction as compared with the case where it is formed at a predetermined position. To do.

  FIG. 11 shows an example of each image transferred to the intermediate transfer belt 26 when an image is formed on an A4 size (SEF) sheet P, for example.

  As shown in FIG. 11, the reference image formed at a position other than the predetermined position on the peripheral surface of the photosensitive drum 30 is formed longer in the circumferential direction than the reference image S formed at the predetermined position. ing.

  FIG. 12 is a flowchart showing the flow of processing of the density correction processing program according to the second embodiment. In addition, the same code | symbol is attached | subjected to the process same as the density | concentration correction process (FIG. 10) of the said 1st Embodiment, and description is abbreviate | omitted.

  In step 250, it is determined whether or not the reference image whose density has been detected is formed at a predetermined position on the circumferential surface of the photosensitive drum 30, and if the determination is affirmative, the process proceeds to step 252, and negative. If it is determined, the process proceeds to step 251.

  In step 251, the density sensor 44 is controlled, and more points (for example, 20) than when the reference image is formed at a predetermined position on the circumferential surface of the photosensitive drum 30 at a predetermined time interval ΔT. The density of the reference image is detected by sampling the reference image transferred to the intermediate transfer body belt 26 and performing an averaging process.

That is, when the reference image is formed at a position other than the predetermined position on the peripheral surface of the photosensitive drum 30, the density detection is performed at more points than when the reference image is formed at the predetermined position. To do. As a result, even if the peripheral surface of the photoconductor drum 30 on which the reference image is formed has scratches or the like, and the density changes suddenly in a part of the reference image, the change in the density of the printed image is suppressed.
[Third Embodiment]
Since the schematic configuration of the image forming apparatus 10 according to the third embodiment, the schematic configuration inside the apparatus main body 14, and the main configuration of the electrical system are the same as those in the first embodiment, description thereof is omitted here. .

  The image forming apparatus 10 according to the third embodiment accepts an operation designation in an image quality priority operation that prioritizes image quality or a speed priority operation that prioritizes image formation speed on the operation screen displayed on the display 16. Further, the image forming apparatus 10 accepts an operation designation in an image quality priority operation or a speed priority operation in an external terminal device. Information regarding the operation designation received by the external terminal device is transmitted to the image forming apparatus 10 via the network NET together with the image information when the printing is instructed. In the present embodiment, the display 16 and an external terminal device correspond to an example of image quality priority operation reception means and speed priority operation reception means.

  When the operation designation in the image quality priority operation or the speed priority operation is accepted, the image forming apparatus 10 executes image formation processing in the designated operation state.

  FIG. 13 is a flowchart showing the flow of processing of the image forming processing program according to the third embodiment. Note that the same processes as those in the image forming process (FIG. 7) of the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  In step 201, it is determined whether or not the received operation designation is an image quality priority operation. If the determination is affirmative, the process proceeds to step 202. If the determination is negative, the process proceeds to step 204.

  In step 202, the value of the number of rotations obtained in step 200 is moved up to the decimal point. Thereby, for example, when the value of the number of rotations is 1.50, the result of carrying up is 2.00.

  In step 209, the operation designation information indicating the accepted operation designation is output to the image forming control unit 114 together with the image interval information and the YMCK color image data.

  When the operation designation indicated by the operation designation information is an image quality priority operation, the image formation control unit 114 according to the third embodiment uses each image forming unit 24 based on the input image interval information and YMCK color image data. Are controlled to form one print image on the peripheral surface of each photoconductive drum 30 for each number of rotations indicated by the image interval information. The image formation control unit 114 forms the reference image on the front side in the rotation direction of the print image by changing the color and density in the predetermined order by the length of the reference image area indicated by the image interval information. Further, if necessary, a toner band is formed.

  On the other hand, when the operation designation indicated by the operation designation information is a speed priority operation, the image formation control unit 114 controls each image forming unit 24 based on the input image interval information and YMCK color image data, One printed image is formed on the peripheral surface of the photosensitive drum 30. Further, the image formation control unit 114 rotates the photosensitive drum 30 that is to form the reference image from the rotational position of the photosensitive drum 30 when the light beam is irradiated from the optical scanning device 38 to form the reference image. The position is derived, and if the derived rotational position is other than a predetermined position on the circumferential surface of the photosensitive drum 30, the next print image is formed by shortening the image interval without forming the reference image. .

  Accordingly, for example, when an image is designated on an A4 size (SEF) sheet P by performing an operation designation of an image quality priority operation, the number of rotations is incremented to an integer value, and as shown in FIG. In addition, every time the photosensitive drum 30 rotates twice, a set of a print image, a reference image, and a toner band is formed.

  On the other hand, for example, when an image is formed on an A4 size (SEF) paper P by specifying the speed priority operation, the rotational position is predetermined on the peripheral surface of the photosensitive drum 30 as shown in FIG. A reference image is not formed at a position other than the set position, and the next print image is formed at a short image interval.

  In each of the embodiments described above, the present invention is applied to an image forming apparatus that forms a color image by forming each color image of YMCK on the photosensitive drum 30 and transferring the color image to the intermediate transfer belt 26 so as to overlap each other. Although the case where the invention is applied has been described, the present invention is not limited to this. For example, the present invention may be applied to an image forming apparatus that forms a monochrome image using only K colors.

  Further, although cases have been described with the above embodiments where density correction is performed by correcting values in a lookup table, the present invention is not limited to this. For example, the driving voltage at the time of outputting the light beam from the optical scanning device 38 may be corrected to change the light amount of the light beam. The charging potential for charging the photosensitive drum 30 by the charger 36 is corrected to correct the photosensitive drum. 30 may be changed, or the toner supply amount may be changed by correcting the developing bias voltage when the toner is adhered to the photosensitive drum 30 from the developing device 40.

  Further, although cases have been described with the above embodiments where a reference image having a plurality of densities is formed for each color of YMCK, the present invention is not limited to this. For example, a reference image having one density may be formed for each color of YMCK.

  In the first embodiment, the cycle of forming one reference image of density Cin = 60% and density Cin = 20% for each color is repeated in the order of YMCK colors, and the density Cin for each color is repeated every cycle. In the above description, the reference image is formed by changing the order of forming the reference image with 60% and the density Cin = 20%. However, the present invention is not limited to this. For example, as shown in FIG. 16, for example, a reference image of YMCK color may be sequentially formed for each density.

  In each of the above embodiments, the case where the number of rotations for rotating the photosensitive drum 30 when forming one set of the print image, the reference image, and the toner band is stored in the sheet interval information has been described. Is not limited to this. For example, the image interval of the print image may be stored. This image interval may be stored as a distance or may be stored as the time at which the image interval is obtained. In addition, when print images are periodically formed on the peripheral surface of the photosensitive drum 30 for each predetermined number, position information such as a start position at which the formation of each print image is started may be stored.

  Further, in each of the above embodiments, the case where the reference image of each color is formed so that the reference image of each color is transferred onto the inter-image portion of each different print image on the intermediate transfer belt 26 has been described. Is not limited to this. For example, the reference image of each color may be transferred to the same image portion on the intermediate transfer belt 26. In this case, the reference image of each color may be formed on the intermediate transfer belt 26 so as not to overlap. For example, when the reference images of the respective colors are formed side by side in the moving direction on the intermediate transfer belt 26, the density of the reference image of each color may be detected by one density sensor 44. For example, when the reference images of the respective colors are formed side by side in the width direction on the intermediate transfer belt 26, a plurality of density sensors 44 are provided in the width direction of the intermediate transfer belt 26 to detect the density of each reference image. do it. When a plurality of density sensors 44 are provided in the width direction of the intermediate transfer body belt 26 as described above, for example, when the position where the reference image is formed is not a predetermined position, the reference image is transferred to the width of the intermediate transfer body belt 26. The number of density detection positions may be increased by increasing the length in the direction and detecting the density of the reference image with the plurality of density sensors 44.

  In each of the above embodiments, the case where the reference image is formed on the front side in the rotation direction of the print image has been described. However, the present invention is not limited to this. For example, the reference image may be formed on the rear side in the rotation direction of the print image, or may be formed on each of the front side and the rear side in the rotation direction.

  In each of the above embodiments, the case where the toner band is removed by the belt cleaner 62 without transferring the reference image onto the paper P by the second transfer unit 46 has been described, but the present invention is limited to this. It is not a thing. For example, the reference image may be transferred to the paper P by the second transfer unit 46 so that the reference image and the toner band are formed separately.

In each of the above embodiments, the case where the density sensor 44 is provided on the intermediate transfer belt 26 has been described. However, the present invention is not limited to this. For example, each photoconductive drum 30 may be provided with a density sensor. Further, for example, when the reference image is transferred to the paper P, the density of the reference image transferred to the paper P may be detected. Each image shown in FIGS. 7 and 13 according to the above embodiment The formation processing program and each density correction processing program shown in FIGS. 10 and 12 are stored in advance in a storage element such as the ROM 102 in addition to a form stored in the ROM 102 in advance, an HDD (hard disk drive) Applicable to forms stored in storage devices such as CD-ROM and DVD-ROM, stored in computer-readable storage media, distributed via wired or wireless communication means, etc. May be.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 16 Display 22 Image forming engine part 24 Image forming unit 26 Intermediate transfer belt 30 Photosensitive drum 36 Charger 38 Optical scanning device 40 Developer 44 Density sensor 100 CPU
102 ROM
106 Non-volatile memory 114 Image formation control unit

Claims (7)

An image carrier that rotates and holds an image formed on the peripheral surface;
The first image is formed one by one on the peripheral surface of the image carrier while shifting the formation position in the rotation direction, and the second image is formed at least on the front side or the rear side in the rotation direction of the first image. Image forming means for
Detecting means for detecting the density of the second image;
When the position where the second image whose density is detected by the detection means is not a predetermined position on the peripheral surface of the image carrier, the correction degree is compared with the case where the position is the predetermined position. Correcting means for correcting the density of the first image formed by the image forming means based on the density of the second image detected by the detecting means,
An image forming apparatus. The image forming apparatus according to claim 1, wherein the image forming unit forms the second image in the inter-image portion when the inter-image portion of the first image is at the predetermined position on the peripheral surface. The image forming unit accepts the operation designation in the image quality priority operation when the image quality priority operation accepting unit accepts the operation designation in the image quality priority operation by the image quality priority operation accepting unit that accepts the operation designation of the image quality priority operation giving priority to the image quality of the image. 2. The second image is formed at the predetermined position on the peripheral surface with a smaller number of rotations of the image carrier by changing an image interval for forming the first image longer than in a case where the first image is not formed. Alternatively, the image forming apparatus according to claim 2. The image forming unit accepts the operation designation in the speed priority operation when the operation designation in the speed priority operation is accepted by the speed priority operation accepting unit that accepts the operation designation of the speed priority operation giving priority to the image forming speed. The frequency of forming the second image is reduced as compared with the case where the first image is not formed, and the first image is formed by changing the image interval at which the first image is formed at least partially to be shorter. Item 4. The image forming apparatus according to any one of Items 3 to 3. The detecting means detects the density of the second image by detecting and averaging the density at a plurality of positions of the second image;
In the case where the image forming unit forms the second image at a position other than the predetermined position, the detection position of the density of the second image by the detecting unit is compared with the case where the second image is formed at the predetermined position. The image forming apparatus according to claim 1, wherein the second image is formed longer in a direction in which the amount of the image increases. Storage means for storing interval information relating to the interval at which the first image is formed on the peripheral surface of the image carrier for each length of the recording medium in the circumferential direction of the image carrier,
The image forming unit includes an interval based on the interval information corresponding to a length in the circumferential direction of a recording medium on which the first image formed on the peripheral surface of the image carrier is transferred directly or via an intermediate transfer member. The image forming apparatus according to claim 1, wherein the first image is formed. Computer
The first image is formed one by one on the peripheral surface of the image carrier that rotates and holds the image formed on the peripheral surface while shifting the formation position in the rotational direction, and at least the first image in the rotational direction is formed. Image forming means for forming a second image on at least one of the front side and the rear side;
When the position where the second image whose density is detected by the detecting means for detecting the density of the second image is not a predetermined position on the peripheral surface of the image holding member, the predetermined position is A correction unit that corrects the density of the first image formed by the image forming unit on the basis of the density of the second image detected by the detection unit by reducing the correction degree as compared with a certain case;
Program to function as.

Images