JP6677001B2 - Image forming apparatus, control method, and control program - Google Patents

Description

  The present disclosure relates to control of an image forming apparatus, and particularly to control of an electrophotographic image forming apparatus.

  Electrophotographic image forming apparatuses have become widespread. An electrophotographic image forming apparatus includes, as a printing process, a process of uniformly charging a photoconductor, a process of exposing the photoconductor to form an electrostatic latent image, and a process of forming an electrostatic latent image on the photoconductor into toner. A step of developing as an image and a step of transferring the toner image on the photoreceptor to a sheet are executed.

  The step of charging the photoreceptor is realized by a charging device. The charging device is provided with a charging roller. The charging roller is in contact with the photoconductor, and charges the photoconductor uniformly by rotating.

  FIG. 15 is a diagram illustrating the photoconductor 10 and the charging roller 12. When a long time elapses from the previous printing, discharge products are generated in the nip adjacent areas A and B adjacent to the nip portion N of the photoconductor 10 and the charging roller 12. The discharge product has a hygroscopic property, and reduces the adsorbing power of the toner on the photoreceptor. As a result, band-like noise occurs in the printed image.

  FIG. 16 is a diagram illustrating an image 60 in which a band-like noise has occurred. The region 60 </ b> N of the image 60 is a portion corresponding to the nip portion N of the photoconductor 10. The area 60 </ b> A of the image 60 is a part corresponding to the nip adjacent area A of the photoconductor 10. The region 60 </ b> B of the image 60 is a portion corresponding to the nip adjacent region B of the photoconductor 10. When the discharge substance is generated on the photoconductor 10, as shown in the image 60, the toner does not adhere to the areas 60A and 60B. As a result, white band noise appears in the regions 60A and 60B, and black band noise appears in the region 60N. The band-like noise is particularly noticeable under high temperature and high humidity.

  As a method for suppressing band-like noise, a method of rotating a photoconductor before starting printing is known. In the following, rotating the photoconductor before starting printing is also referred to as “idling”. As the photoconductor rotates idle, discharge products on the photoconductor are removed.

  Japanese Patent Application Laid-Open No. 2007-316141 (Patent Document 1) discloses an image forming apparatus that performs idle rotation under high temperature and high humidity. More specifically, the image forming apparatus has a sensor that detects temperature and humidity. The image forming apparatus executes idle rotation of the photoconductor when the temperature and humidity detected by the sensor are equal to or higher than predetermined values.

JP 2007-316141 A

  The image forming apparatus disclosed in Patent Literature 1 always idles the photoconductor when the temperature and the humidity detected by the sensor are equal to or higher than predetermined values. Since the photoconductor and the charging roller are in contact, the photoconductor wears as it rotates. Therefore, if the photoconductor is idled excessively, the pace at which the photoconductor is worn is increased, and the life of the photoconductor is shortened. Therefore, an image forming apparatus capable of suppressing abrasion of the photoconductor due to idling has been desired. At this time, it is also desired that the print quality does not deteriorate.

  SUMMARY An advantage of some aspects of the disclosure is to provide an image forming apparatus capable of suppressing abrasion of a photoconductor while suppressing a decrease in print quality. It is to be. Another object of the present invention is to provide a control method capable of suppressing abrasion of a photoconductor while suppressing a decrease in print quality. It is still another object of the present invention to provide a control program capable of suppressing abrasion of a photoreceptor while suppressing a decrease in print quality.

  According to one aspect, an image forming apparatus having a printing function includes a photoconductor, a charging roller that is in contact with the photoconductor, and charges the photoconductor, and a photoconductor that is charged by the charging roller. An exposure device for forming an electrostatic latent image corresponding to an input image, a developing device for developing the electrostatic latent image formed on the photoconductor, and a device for controlling rotation of the photoconductor. Control device. The control device detects, in the input image, an intermediate density portion whose pixel value falls within a predetermined range, and reduces the number of rotations of the photoconductor before starting printing as the area of the intermediate density portion decreases.

  Preferably, when the area of the intermediate density portion is smaller than a predetermined value, the control device does not execute the rotation of the photoconductor before starting printing.

  Preferably, the rotation speed of the photoconductor before starting printing is predetermined as a default rotation speed. The control device reduces the default rotation speed as the area of the intermediate density portion decreases.

  Preferably, the control device, when receiving a print instruction for a plurality of input images, for each of the input images that can be printed when the photoconductor is tentatively rotated by the default number of rotations, the intermediate density portion The area is detected, and if all of the detected areas are smaller than the predetermined value, the rotation of the photoconductor before starting printing is not performed.

  Preferably, when the input image in which the area of the intermediate density portion is smaller than the predetermined value is continuous from the first print, the control device is configured to print the continuous input image. The rotation speed of the photoconductor is calculated, and the rotation of the photoconductor before the start of printing is performed by the difference of the rotation speed from the default rotation speed.

  Preferably, the developing device develops the electrostatic latent image formed on the photoconductor as a toner image. The control device specifies an image portion corresponding to the intermediate density portion from the toner image, and a region adjacent to a nip portion between the photoconductor and the charging roller before printing starts corresponds to the image portion after printing starts. If it is determined that the image portion does not hit the adjacent area, the rotation of the photoconductor before starting printing is not performed.

  Preferably, when the control device determines that the image portion hits the adjacent region, the control device rotates the photoconductor so that the image portion does not hit the adjacent region, and then transfers the toner image to the photosensitive region. Form on the body.

  Preferably, the control device reduces the number of rotations of the photoconductor before starting printing as the pixel value in the input image is larger.

  Preferably, the control device reduces the number of rotations of the photoconductor before the start of printing, as the time from the end of the previous printing to the start of the current printing is shorter.

  Preferably, the control device reduces the number of rotations of the photoconductor before the start of printing, as the number of prints in the past fixed period is smaller.

  Preferably, the image forming apparatus further includes a sensor for detecting humidity inside the image forming apparatus. The control device reduces the number of rotations of the photoconductor before starting printing, as the humidity detected by the sensor is smaller.

  According to another aspect, a method for controlling an image forming apparatus having a printing function is provided. The image forming apparatus includes a photoconductor, a charging roller that is in contact with the photoconductor, and charges the photoconductor, and an electrostatic image corresponding to an input image on the photoconductor charged by the charging roller. An exposure device for forming a latent image and a developing device for developing the electrostatic latent image formed on the photoconductor are provided. The control method includes the steps of: detecting, in the input image, an intermediate density portion whose pixel value falls within a predetermined range; and reducing the number of rotations of the photoconductor before starting printing as the area of the intermediate density portion decreases. And

  According to yet another aspect, a control program for an image forming apparatus having a printing function is provided. The image forming apparatus includes a photoconductor, a charging roller that is in contact with the photoconductor, and charges the photoconductor, and an electrostatic image corresponding to an input image on the photoconductor charged by the charging roller. An exposure device for forming a latent image and a developing device for developing the electrostatic latent image formed on the photoconductor are provided. The control program includes, in the image forming apparatus, a step of detecting an intermediate density portion in which a pixel value falls within a predetermined range in the input image; and the smaller the area of the intermediate density portion is, the smaller the area of the photoconductor is before starting printing. And reducing the number of revolutions.

In one aspect, it is possible to suppress the wear of the photoreceptor while suppressing a decrease in print quality.
The above and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the invention that is understood in connection with the accompanying drawings.

FIG. 2 is a diagram illustrating an example of an internal structure of the image forming apparatus. FIG. 7 is a diagram illustrating three output images having different densities. FIG. 9 is a diagram illustrating an experimental result for examining an idle rotation number of a photoconductor necessary for suppressing band-shaped noise. 5 is a flowchart illustrating a process executed by the image forming apparatus. FIG. 6 is a diagram for explaining a control example 1 of the photoconductor. FIG. 9 is a diagram for explaining a control example 2 of the photoconductor. 9 is a flowchart illustrating a control example 2 of the photoconductor. FIG. 9 is a diagram for explaining a control example 3 of the photoconductor. 9 is a flowchart illustrating a control example 3 of the photoconductor. FIG. 9 is a diagram for explaining a control example 4 of the photoconductor. FIG. 14 is a diagram for explaining a control example 5 of the photoconductor. FIG. 14 is a diagram for explaining a control example 6 of the photoconductor. FIG. 14 is a diagram for explaining a control example 7 of the photoconductor. FIG. 2 is a block diagram illustrating a main hardware configuration of the image forming apparatus. FIG. 3 is a diagram illustrating a photoconductor and a charging roller. FIG. 5 is a diagram illustrating an image in which band-like noise is generated.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are the same. Therefore, detailed description thereof will not be repeated. In addition, each embodiment and each modification described below may be appropriately and selectively combined.

<First embodiment>
[Internal Structure of Image Forming Apparatus 100]
With reference to FIG. 1, an image forming apparatus 100 according to the embodiment will be described. FIG. 1 is a diagram illustrating an example of the internal structure of the image forming apparatus 100.

  FIG. 1 shows an image forming apparatus 100 as a color printer. Hereinafter, the image forming apparatus 100 as a color printer will be described, but the image forming apparatus 100 is not limited to a color printer. For example, the image forming apparatus 100 may be a monochrome printer, a facsimile, or a multi-function peripheral (MFP: Multi-Functional Peripheral) of a monochrome printer, a color printer, and a facsimile.

  The image forming apparatus 100 includes an image forming unit 1Y, 1M, 1C, 1K, an intermediate transfer belt 30, a primary transfer roller 31, a secondary transfer roller 33, a cassette 37, a driven roller 38, and a drive roller 39. , A timing roller 40, a cleaning device 42, a fixing device 50, and a control device 101.

  The image forming unit 1Y receives a supply of toner from the toner bottle 15Y and forms a yellow (Y) toner image on the photoconductor 10. The image forming unit 1M forms a magenta (M) toner image on the photoreceptor 10 by receiving toner from the toner bottle 15M. The image forming unit 1C forms a cyan (C) toner image on the photoconductor 10 by receiving toner from the toner bottle 15C. The image forming unit 1K forms a black (BK) toner image on the photoconductor 10 by receiving toner from the toner bottle 15K. That is, the photoconductor 10 is provided for forming a toner image of a specific color.

  The image forming units 1 </ b> Y, 1 </ b> M, 1 </ b> C, and 1 </ b> K are arranged in the rotation direction of the intermediate transfer belt 30 along the intermediate transfer belt 30. Each of the image forming units 1Y, 1M, 1C, and 1K includes a rotatable photoconductor 10, a charging device 11, an exposure device 13, a developing device 14, and a cleaning device 17.

  The charging device 11 uniformly charges the surface of the photoconductor 10 to a predetermined potential. As a charging method by the charging device 11, for example, a charging roller method is adopted. The charging device 11 includes a rotatable charging roller 12. The charging roller 12 is in contact with the photoconductor 10. As a result, a nip portion N is formed between the photoconductor 10 and the charging roller 12.

  The exposure device 13 irradiates the photoconductor 10 with laser light in response to a control signal from the control device 101, and exposes the surface of the photoconductor 10 according to input image information. That is, the exposure device 13 forms an electrostatic latent image on the photoconductor 10 charged by the charging device 11 according to the image information of the input image. As a result, an electrostatic latent image corresponding to the input image is formed on the photoconductor 10.

  The developing device 14 develops the electrostatic latent image formed on the photoconductor 10 as a toner image. More specifically, the developing device 14 applies a developing bias to the developing roller 15 while rotating the developing roller 15, and causes the toner to adhere to the surface of the developing roller 15. As a result, the toner is transferred from the developing roller 15 to the photoconductor 10, and a toner image corresponding to the electrostatic latent image is developed on the surface of the photoconductor 10.

  The photoconductor 10 and the intermediate transfer belt 30 are in contact with each other at a portion where the primary transfer roller 31 is provided. When a transfer voltage having a polarity opposite to that of the toner image is applied to the primary transfer roller 31, the toner image is transferred from the photoconductor 10 to the intermediate transfer belt 30. A yellow (Y) toner image, a magenta (M) toner image, a cyan (C) toner image, and a black (BK) toner image are sequentially superimposed and transferred from the photoconductor 10 to the intermediate transfer belt 30. As a result, a color toner image is formed on the intermediate transfer belt 30.

  The intermediate transfer belt 30 is stretched around a driven roller 38 and a driving roller 39. The drive roller 39 is connected to a motor (not shown). When the control device 101 controls the motor, the drive roller 39 rotates. The intermediate transfer belt 30 and the driven roller 38 rotate in conjunction with the driving roller 39. As a result, the toner image on the intermediate transfer belt 30 is transported to the secondary transfer roller 33.

  The cleaning device 17 collects toner remaining on the surface of the photoconductor 10 after the transfer of the toner image from the photoconductor 10 to the intermediate transfer belt 30.

  Paper S is set in the cassette 37. The sheet S is sent from the cassette 37 to the secondary transfer roller 33 along the transport path 41 by the timing roller 40 one by one. The control device 101 controls the transfer voltage applied to the secondary transfer roller 33 in accordance with the timing at which the sheet S is sent out.

  The secondary transfer roller 33 applies a transfer voltage having a polarity opposite to that of the toner image to the sheet S being transported. As a result, the toner image is attracted from the intermediate transfer belt 30 to the secondary transfer roller 33, and the toner image on the intermediate transfer belt 30 is transferred. The timing of conveying the sheet S to the secondary transfer roller 33 is controlled by the timing roller 40 in accordance with the position of the toner image on the intermediate transfer belt 30. As a result, the toner image on the intermediate transfer belt 30 is transferred to an appropriate position on the sheet S.

  The fixing device 50 pressurizes and heats the sheet S passing therethrough. Thus, the toner image is fixed on the sheet S. Thereafter, the sheet S is discharged to the tray 48.

  The cleaning device 42 collects toner remaining on the surface of the intermediate transfer belt 30 after the transfer of the toner image from the intermediate transfer belt 30 to the sheet S. The collected toner is transported by a transport screw (not shown) and stored in a waste toner container (not shown).

[Control of idle rotation]
With reference to FIG. 2, a control method of the photoconductor 10 will be described. Hereinafter, an image input to the image forming apparatus 100 as a print target is also referred to as an “input image”, and an image output as a print result is also referred to as an “output image”. FIG. 2 is a diagram showing three output images having different densities.

  When a long time elapses from the previous printing, discharge products are generated in the nip adjacent areas A and B (see FIG. 1) adjacent to the nip portion N (see FIG. 1). When a discharge product is generated, band-like noise is generated in an output image.

  FIG. 2A shows an output image 61A. The output image 61A has a band-like noise. The region 62N of the output image 61A is a portion corresponding to the nip portion N of the photoconductor 10. The area 62A of the output image 61A is a part corresponding to the nip adjacent area A of the photoconductor 10. The region 62B of the output image 61A is a portion corresponding to the nip adjacent region B of the photoconductor 10. When a discharge substance is generated in the photoconductor 10, white band-shaped noise appears in the regions 62A and 62B, and black band-shaped noise appears in the region 62N. The band-shaped noise appears at every ten circumferences W of the photoconductor.

  Such band-shaped noise is eliminated by idling the photoconductor 10. Here, idle rotation refers to rotation of the photoconductor 10 before printing is started before a toner image is formed on the photoconductor 10.

  FIG. 2B shows an output image 61B. The density of the output image 61B is higher than that of the output image 61A. As shown in the output image 61B, when the density increases, no band-like noise is generated. Therefore, when an image having a high density is printed, it is not necessary to perform idle rotation of the photoconductor 10.

  FIG. 2C shows an output image 61C. The output image 61C is a white image. As shown in the output image 61C, when a toner image is not formed, no band-like noise occurs. Therefore, when a white image is printed, it is not necessary to perform idle rotation of the photoconductor 10.

  Therefore, when the intermediate density portion is large in the input image, the idling speed does not need to be executed. Focusing on this point, the image forming apparatus 100 detects, in the input image to be printed, an intermediate density portion whose pixel value falls within a predetermined range (hereinafter, also referred to as an “intermediate range”), and detects the intermediate density portion. The smaller the area, the smaller the number of idle rotations of the photoconductor 10. Thereby, the image forming apparatus 100 can reduce the number of idle rotations of the photoconductor 10, and as a result, the life of the photoconductor 10 is extended. Further, when the intermediate density portion is small, no band-like noise is generated, so that even if the number of idle rotations of the photoconductor 10 decreases, the print quality does not decrease.

  Hereinafter, more specific processing of the photoconductor 10 will be described. A pixel value is associated with each pixel of the input image to be printed. The magnitude of each pixel value correlates with the amount of toner attached. That is, the larger the pixel value of the input image, the higher the toner density in the corresponding pixel of the output image. The control device 101 of the image forming apparatus 100 determines whether each pixel of the input image is within the intermediate range. The intermediate range is represented by a lower limit pixel value and an upper limit pixel value. The lower limit pixel value and the upper limit pixel value are defined in advance. The control device 101 detects a pixel belonging to an intermediate range among the pixels of the input image as an intermediate density portion.

  After that, the control device 101 calculates the area of the intermediate density portion. As an example of a method of calculating the area of the intermediate density portion, the control device 101 counts the number of pixels in the intermediate density portion of the input image and calculates the count result as the area of the intermediate density portion.

  The control device 101 reduces the idle speed of the photoconductor 10 as the area of the intermediate density portion is smaller. Preferably, when the calculated area of the intermediate density portion is smaller than a predetermined value, control device 101 does not execute idle rotation of photoconductor 10. The magnitude of the predetermined value is determined in advance by an experiment or the like. Thereby, abrasion of the photoconductor 10 can be more reliably suppressed.

  When the input image to be printed is a line image composed of characters, straight lines, and the like, the intermediate density portion does not exist in the input image. For this reason, the control device 101 determines whether or not the input image is a line image, and when it is determined that the input image is a line image, it is not necessary to execute the idle rotation of the photoconductor 10. As an example of a line image detection method, the control device 101 detects an edge portion from an input image. If the area of the edge portion is larger than a predetermined value, it is determined that the input image is a line image.

[Default rotation speed]
The idling speed of the photoconductor 10 necessary for suppressing the band noise is predetermined as a default speed. The image forming apparatus 100 reduces the idling speed according to the area of the intermediate density portion based on the default rotating speed, and executes idling of the photoconductor 10 by the adjusted default rotating speed.

  The default rotation speed will be described with reference to FIG. FIG. 3 is a diagram showing an experimental result 80 for examining the idling speed of the photoconductor 10 necessary for suppressing band-like noise. The experiment was performed under the following conditions (1) to (4).

Absolute humidity: 26 (temperature 30 ° C, humidity 85%) ... (1)
Image density: 25% of the maximum density (2)
Idle time before printing: 1 hour (3)
Number of prints before printing: 20 sheets (4)
“X” in the experimental result 80 indicates that band-shaped noise appears in the output image. “△” in the experimental result 80 indicates that a band-like noise appears slightly in the output image. “O” in the experimental result 80 indicates that no band-shaped noise appears in the output image.

  From the experimental results 80, it is necessary to execute 24 idle rotations in order to suppress the band-like noise. That is, under the above conditions, if the idle rotation of 24 rotations is performed before the start of printing, the band-like noise does not occur reliably. Therefore, under the above conditions, the default rotation speed is set to 24 times.

  As described above, when the intermediate density portion is small in the input image, no band noise occurs. Therefore, the control device 101 of the image forming apparatus 100 lowers the default rotation speed as the area of the intermediate density portion of the input image is smaller. Thus, the image forming apparatus 100 can reduce the idle speed while more accurately suppressing the deterioration of the print quality.

  In the above description, an example in which the default rotation speed is set to 24 times has been described, but the default rotation speed may be set to other than 24 times. The default rotation speed can be set to an arbitrary value because it is determined by an experiment or the like.

[Control Structure of Image Forming Apparatus 100]
With reference to FIG. 4, a control structure of image forming apparatus 100 will be described. FIG. 4 is a flowchart illustrating a process executed by image forming apparatus 100. 4 is realized by the control device 101 executing a program. In other aspects, some or all of the processing may be performed by circuit elements or other hardware.

  In step S10, the control device 101 determines whether a print instruction has been received. When determining that a print instruction has been received (YES in step S10), control device 101 switches control to step S12. If not (NO in step S10), the process of step S10 is executed again.

  In step S12, the control device 101 detects an intermediate density portion from the input image to be printed. More specifically, the control device 101 detects a pixel whose pixel value is within a predetermined range from among the pixels of the input image, and detects the pixel group as an intermediate density portion.

  In step S14, the control device 101 calculates an area in the intermediate density portion of the input image. As an example, the area corresponds to the number of pixels in the intermediate density portion.

  In step S20, the control device 101 determines whether or not the intermediate density portion of the input image is smaller than a predetermined value. The magnitude of the predetermined value is predetermined by an experiment or the like. When determining that the intermediate density portion of the input image is smaller than the predetermined value (YES in step S20), control device 101 switches the control to step S50. Otherwise (NO in step S20), control device 101 switches control to step S40.

  In step S40, the control device 101 executes the idle rotation of the photoconductor 10 by the default rotation speed. As described above, the default rotation speed is determined in advance by experiments or the like. The control device 101 prevents band-shaped noise from being generated in the output image due to the idle rotation of the photoconductor 10.

  In step S50, the control device 101 executes printing of the input image. That is, when it is determined in step S20 that the intermediate density portion of the input image is smaller than the predetermined value, the control device 101 executes the printing process in step S50 without executing the idle rotation in step S40. . Therefore, the control device 101 can suppress unnecessary idle rotation, and as a result, can slow down the pace at which the photoconductor 10 is worn.

[Control Example of Photoconductor 10]
With reference to FIGS. 5 to 13, specific control examples 1 to 7 in idling of the photoconductor 10 will be described.

  In the following, a description will be given of a “line image” or a “white image” as an example of an input image in which no band-shaped noise occurs. A description will be given of an “intermediate density image” as an example of an input image in which band-like noise occurs.

  A line image refers to an image composed of characters, straight lines, and the like. The line image has a small area of the intermediate density partial image. Therefore, no band-like noise occurs in the line image.

  Since the toner image is not formed on the white image, the area of the intermediate density partial image is small. Therefore, no band-like noise occurs in the white image.

  The intermediate density image is an image in which the area of the intermediate density portion is equal to or larger than a predetermined value. Therefore, a band-like noise may occur in the intermediate density image.

(Example 1 of idle rotation control)
With reference to FIG. 5, a control example 1 of idling of the photoconductor 10 will be described. FIG. 5 is a diagram for explaining control example 1 of the photoconductor 10.

  In FIG. 5, a plurality of input images are arranged in chronological order. It is assumed that the image forming apparatus 100 has received a print instruction for the plurality of input images. Based on this, the control device 101 of the image forming apparatus 100 calculates the number of input images that can be printed if the photoconductor 10 is provisionally rotated by the default rotation speed. In the example of FIG. 5, the default rotation speed is N rotations. When one input image can be printed every three rotations of the photoconductor 10, the number of input images that can be printed at the default rotation speed is “N rotations ÷ 3 rotations”.

  The control device 101 detects the area of the intermediate density portion for each of the input images that can be printed at the default rotation speed. Control device 101 determines whether each of the detected areas is smaller than a predetermined value. If the control device 101 determines that all of the detected areas are smaller than the predetermined value, the control device 101 does not execute the idle rotation of the photoconductor 10 before the start of printing.

  As an example, it is assumed that all the input images that have received the print instruction are line images. When all the input images are line images, the area of the intermediate density portion in all the input images becomes smaller than a predetermined value. No band noise occurs in the line image. Therefore, when all of the input images are line images, the control device 101 does not execute the rotation of the photoconductor 10 before the start of printing.

(Example 2 of idle rotation control)
With reference to FIG. 6, a control example 2 of idle rotation of the photoconductor 10 will be described. FIG. 6 is a diagram for explaining Control Example 2 of the photoconductor 10.

  In FIG. 6, a plurality of input images are arranged in chronological order. It is assumed that the image forming apparatus 100 has received a print instruction for the plurality of input images. Based on this, the control device 101 of the image forming apparatus 100 sequentially determines whether or not the area of the intermediate density portion is smaller than a predetermined value from the first input image of the print. The control device 101 detects the number of continuous input images in which the area of the intermediate density portion is smaller than a predetermined value. Thereafter, the control device 101 calculates the number of rotations of the photoconductor 10 required to print the input image corresponding to the number of continuations. Since no band-like noise is generated in the continuous input image, the control device 101 does not need to execute the idle rotation of the photoconductor 10 for the continuous input image. Therefore, the control device 101 executes the idle rotation of the photoconductor 10 by an amount corresponding to the difference between the default rotation speed and the calculated rotation speed.

  For example, as shown in FIG. 6, it is assumed that a plurality of line images continue from the first print sheet. Since the band-like noise does not occur in the line image, it is not necessary to perform the idle rotation of the photoconductor 10 for the line image that is continuous from the first print. The control device 101 calculates the number of rotations of the photoconductor 10 required to print a continuous line image. The control device 101 executes the idle rotation of the photoconductor 10 before the start of printing by an amount corresponding to the difference between the calculated rotation speed and the default rotation speed.

  In the example of FIG. 6, the line image continues from the first rotation of the photoconductor 10 to the M-1 rotation. An intermediate density image is printed from the Mth rotation of the photoconductor 10. When the default rotation speed is N rotations, the control device 101 executes idle rotation by NM rotations obtained by subtracting M rotations from N rotations. As a result, the image forming apparatus 100 can suppress the number of idle rotations of the photoconductor 10 even when the input image includes the intermediate density image.

  With reference to FIG. 7, control example 2 of the photoconductor 10 will be further described. FIG. 7 is a flowchart illustrating a control example 2 of the photoconductor 10. The processing in FIG. 7 is realized by the control device 101 executing a program. In other aspects, some or all of the processing may be performed by circuit elements or other hardware. The processes in steps S10, S12, S14, and S50 are the same as those described with reference to FIG. 4, and therefore, description thereof will not be repeated.

  In step S20A, the control device 101 determines whether the area of the intermediate density portion is smaller than a predetermined value in all the input images to be printed. When determining that the area of the intermediate density portion is smaller than the predetermined value in all the input images to be printed (YES in step S20A), control device 101 switches the control to step S50. Otherwise (NO in step S20A), control device 101 switches control to step S30.

  In step S30, the control device 101 determines whether or not the intermediate density portion of the first print input image is smaller than a predetermined value. If the control device 101 determines that the intermediate density portion of the first print input image is smaller than the predetermined value, the control device 101 determines that the first print input image is a line image or a white image. When determining that the first input image to be printed is a line image or a white image (YES in step S30), control device 101 switches control to step S40. Otherwise (NO in step S30), control device 101 switches control to step S32.

  In step S32, the control device 101 detects whether the white image and the line image are continuous from the first print to the number of prints. The control device 101 calculates the number of rotations of the photoconductor 10 necessary for printing a continuous white image and line image from the first sheet.

  In step S34, the control device 101 subtracts the rotation speed calculated in step S32 from the default rotation speed. That is, the control device 101 reduces the default rotation speed by the rotation speed calculated in step S32.

  In step S40, the control device 101 executes idle rotation of the photoconductor 10 by the current default rotation speed.

(Example 3 of idle rotation control)
With reference to FIG. 8, a third example of idle rotation control of the photoconductor 10 will be described. FIG. 8 is a diagram for explaining Control Example 3 of the photoconductor 10.

  FIG. 8 shows a toner image 71 formed on the photoconductor 10. The toner image 71 is formed according to an image pattern in an input image. The toner image 71 has an image portion 72. The image portion 72 corresponds to an intermediate density portion in the input image.

  FIG. 8 shows nip adjacent areas 73A to 73D. The nip adjacent areas 73A to 73D correspond to areas adjacent to a nip portion between the photoconductor 10 and the charging roller 12 before printing is started. If the image portion 72 hits the nip adjacent regions 73A to 73D when printing is started, a band-like noise appears in the output image. If the image portion 72 does not hit the nip adjacent regions 73A to 73D, no band-like noise appears in the output image. Focusing on this point, when the image portion 72 hits the nip adjacent regions 73A to 73D, the image forming apparatus 100 controls the photoconductor 10 before starting printing so that the image portion 72 does not hit the nip adjacent regions 73A to 73D. Stagger the rotation of.

  As a more specific process, the control device 101 of the image forming apparatus 100 specifies, from the toner image 71, an image portion 72 corresponding to the intermediate density portion of the input image. Thereafter, the control device 101 specifies a position on the photoconductor 10 where the image portion 72 is formed. The position of the image portion 72 on the photoconductor 10 is specified based on image information generated when a print instruction is received.

  The control device 101 determines whether or not the nip adjacent regions 73A to 73D before the start of printing hit the image portion 72 after the start of printing. When determining that the image portion 72 does not hit the nip adjacent regions 73A to 73D, the control device 101 does not execute the idle rotation of the photoconductor 10 before the start of printing. This is because when the image portion 72 does not hit the nip adjacent regions 73A to 73D, no band-like noise occurs in the output image. By suppressing excess idle rotation, the image forming apparatus 100 can delay the pace at which the photoconductor 10 is worn.

  When the control device 101 determines that the image portion 72 hits the nip adjacent regions 73A to 73D, it starts printing after rotating the photoconductor 10 so that the image portion 72 does not hit the nip adjacent regions 73A to 73D. . That is, when the rotation is executed, the control device 101 does not execute the idle rotation of the photoconductor 10. Thereby, the control device 101 can further reduce the number of idle rotations of the photoconductor 10.

  The control example 3 of the photoconductor 10 will be further described with reference to FIG. FIG. 9 is a flowchart illustrating a third control example of the photoconductor 10. The processing in FIG. 9 is realized by the control device 101 executing a program. In other aspects, some or all of the processing may be performed by circuit elements or other hardware. The processes other than steps S22, S24, and S26 are the same as those described with reference to FIG. 4, and therefore, description thereof will not be repeated.

  In step S22, the control device 101 determines whether or not the intermediate density portion of the input image falls on the nip adjacent region when printing is started. If the control device 101 determines that the intermediate density portion of the input image falls on the nip adjacent region when printing is started (YES in step S22), the control device 101 switches the control to step S24. Otherwise (NO in step S22), control device 101 switches control to step S50.

  In step S24, the control device 101 determines whether the photoconductor 10 can be rotated so that the intermediate density portion of the input image does not hit the nip adjacent area. As an example, when the width of the intermediate density portion is shorter than the circumference of the photoconductor 10, the control device 101 determines that the photoconductor 10 can be rotated so that the intermediate density portion of the input image does not hit the nip adjacent area. . When the control device 101 determines that the photoconductor 10 can be rotated so that the intermediate density portion of the input image does not hit the nip adjacent area (YES in step S24), the control is switched to step S26. Otherwise (NO in step S24), control device 101 switches control to step S40.

  In step S26, the control device 101 rotates the photoconductor 10 so that the intermediate density portion of the input image does not hit the nip adjacent area. Thus, even when the intermediate density portion is included in the input image, the control device 101 can reduce the idle speed of the photoconductor 10.

(Example 4 of idle rotation control)
With reference to FIG. 10, a control example 4 of idle rotation of the photoconductor 10 will be described. FIG. 10 is a diagram for explaining a control example 4 of the photoconductor 10.

  FIG. 10 shows an experimental result 82. The experimental result 82 is a result of examining the relationship between the density of the output image in which no band-like noise is generated and the idle speed. The experiment was performed under the following conditions (5) to (7).

Absolute humidity: 26 (temperature 30 ° C, humidity 85%) (5)
Idle time before starting printing: 1 hour (6)
Number of prints before printing: 20 sheets (7)
The image density shown in the experimental result 82 is, for example, the average density of each pixel of the output image. “×” in the experimental result 82 indicates that band-like noise appears in the output image. “Δ” in the experimental result 82 indicates that a band-like noise appears slightly in the output image. “O” in the experimental result 82 indicates that no band-shaped noise appears in the output image.

  As shown in the experimental result 82, the idle rotation speed may be lower as the image density is higher. The reason for this is that as the image density increases, the difference in contrast decreases. Focusing on this point, the control device 101 of the image forming apparatus 100 reduces the idle rotation number of the photoconductor 10 before the start of printing as the pixel value in the input image increases. Pixel values in the input image correlate with density.

  As an example, when the density of the output image is greater than 75% and equal to or less than 100%, the image forming apparatus 100 sets the default rotation speed to zero. When the density of the output image is larger than 50% and equal to or smaller than 75%, the image forming apparatus 100 sets the default rotation speed to 12 times. When the density of the output image is greater than 25% and equal to or less than 50%, the image forming apparatus 100 sets the default rotation speed to 20 times. When the density of the output image is 0% or more and 25% or less, the image forming apparatus 100 sets the default rotation speed to 24 times.

(Example 5 of idle rotation control)
With reference to FIG. 11, control example 5 of idling of the photoconductor 10 will be described. FIG. 11 is a diagram for explaining a control example 5 of the photoconductor 10.

  FIG. 11 shows an experimental result 84. The experimental result 84 is a result of examining the relationship between the idle time of the photoconductor 10 where no band-shaped noise is generated and the idle speed. The experiment was performed under the following conditions (8) to (10).

Absolute humidity: 26 (temperature 30 ° C, humidity 85%) (8)
Image density: 25% of maximum density (9)
Number of printed sheets before starting printing: 20 sheets (10)
The idle time shown in the experimental result 84 is the time from the end of the previous printing to the start of the current printing. Stated differently, the standing time shown in the experimental result 84 represents the time from when the photosensitive member 10 stops until the rotation of the photosensitive member 10 starts next. “×” in the experimental result 84 indicates that band-like noise appears in the output image. “△” in the experimental result 84 indicates that a band-like noise appears slightly in the output image. “O” in the experimental result 84 indicates that no band-shaped noise appears in the output image.

  As shown in the experimental results 84, the idle rotation speed may be lower as the photoconductor 10 is left for a shorter time. The reason for this is that the shorter the standing time of the photoconductor 10, the smaller the amount of discharge products generated on the photoconductor 10. Focusing on this point, the control device 101 of the image forming apparatus 100 determines that the shorter the time from the end of the previous printing to the start of the current printing (that is, the idle time of the photoconductor 10), the shorter the printing time. The idling speed of the photoconductor 10 before the start is reduced.

  More specifically, the control device 101 starts counting time when printing is completed. As an example, a clock function provided in the control device 101 is used for counting time. The control device 101 stops counting time based on accepting a new print instruction. The control device 101 detects the count result of the time as the idle time of the photoconductor 10.

  As an example, when the photoreceptor 10 is left for 10 minutes or less, the image forming apparatus 100 sets the default rotation speed to 0. If the time for which the photoconductor 10 is left is longer than 10 minutes and equal to or shorter than 1 hour, the image forming apparatus 100 sets the default rotation speed to 24 times. If the time for which the photoconductor 10 is left is longer than 1 hour and not longer than 24 hours, the image forming apparatus 100 sets the default rotation speed to 28 times. If the photoconductor 10 has been left for more than 24 hours, the image forming apparatus 100 sets the default rotation speed to 32 times.

(Example 6 of idle rotation control)
With reference to FIG. 12, control example 6 of idling of the photoconductor 10 will be described. FIG. 12 is a diagram for explaining a control example 6 of the photoconductor 10.

  FIG. 12 shows an experimental result 86. The experimental result 86 is the result of examining the relationship between the previous number of printed sheets and the number of idle rotations at which no band-shaped noise occurs. The experiment was performed under the following conditions (11) to (113).

Absolute humidity: 26 (temperature 30 ° C, humidity 85%) (11)
Image density: 25% of maximum density (12)
Idle time before printing: 1 hour (13)
The number of printed images in the past fixed period shown in the experimental result 86 indicates the number of input images printed in the past fixed period (for example, one hour) from the time of this printing. “X” in the experimental result 86 indicates that band-shaped noise appears in the output image. “Δ” in the experimental result 86 indicates that a band-like noise appears slightly in the output image. “O” in the experimental result 86 indicates that no band-shaped noise appears in the output image.

  As shown in the experimental result 86, the idle rotation speed may be lower as the number of prints in the past fixed period is smaller. The reason for this is that the smaller the number of printed sheets in the past fixed period, the smaller the amount of discharge products generated on the photoconductor 10. Focusing on this point, the control device 101 of the image forming apparatus 100 reduces the idle rotation number of the photoconductor 10 before the start of printing as the number of prints in the past fixed period is smaller.

  As an example, when the number of prints in the past fixed period is 20 or less, the image forming apparatus 100 sets the default rotation speed to 0. If the number of prints in the past fixed period is more than 20 and not more than 100, the image forming apparatus 100 sets the default rotation speed to 24. When the number of prints in the past fixed period is more than 100 and 500 or less, the image forming apparatus 100 sets the default rotation speed to 28 times. If the number of prints in the past fixed period is more than 500, the image forming apparatus 100 sets the default rotation speed to 32 times.

(Example 7 of idle rotation control)
With reference to FIG. 13, a control example 7 of idle rotation of the photoconductor 10 will be described. FIG. 13 is a diagram for explaining a control example 7 of the photoconductor 10.

  FIG. 13 shows an experimental result 88. The experimental result 88 is a result of examining the relationship between the absolute humidity at which no band-shaped noise is generated and the idling speed. The experiment was performed under the following conditions (14) to (16).

Image density: 25% of maximum density (14)
Idle time before starting printing: 1 hour (15)
Number of prints before printing: 20 sheets (16)
The absolute humidity shown in the experiment result 88 is detected by the humidity sensor 108 (see FIG. 14) provided inside the image forming apparatus 100. “X” in the experimental result 88 indicates that band-shaped noise appears in the output image. “Δ” in the experimental result 88 indicates that a band-like noise appears slightly in the output image. “O” in the experimental result 88 indicates that no band-shaped noise appears in the output image.

  As shown in the experimental result 88, the smaller the absolute humidity, the lower the idle speed may be. The reason is that the smaller the absolute humidity is, the smaller the amount of the discharge product generated on the photoconductor 10 is. Focusing on this point, the controller 101 of the image forming apparatus 100 reduces the idle rotation number of the photoconductor 10 before the start of printing as the humidity detected by the humidity sensor is smaller.

  For example, when the absolute humidity is equal to or less than “10”, the image forming apparatus 100 sets the default rotation speed to 0. If the absolute humidity is greater than “10” and equal to or less than “16”, the image forming apparatus 100 sets the default rotation speed to 16 times. If the absolute humidity is larger than “16” and equal to or smaller than “26”, the image forming apparatus 100 sets the default rotation speed to 20 times. If the absolute humidity is higher than “26”, the image forming apparatus 100 sets the default rotation speed to 24 times.

[Hardware Configuration of Image Forming Apparatus 100]
An example of a hardware configuration of the image forming apparatus 100 will be described with reference to FIG. FIG. 14 is a block diagram illustrating a main hardware configuration of the image forming apparatus 100.

  As shown in FIG. 14, the image forming apparatus 100 includes a fixing device 50, a control device 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, a network interface 104, and an operation panel 107. , A humidity sensor 108, and a storage device 120.

  The control device 101 is composed of, for example, at least one integrated circuit. The integrated circuit includes, for example, at least one CPU (Central Processing Unit), at least one ASIC (Application Specific Integrated Circuit), at least one FPGA (Field Programmable Gate Array), or a combination thereof.

  Control device 101 controls the operation of image forming apparatus 100 by executing various programs such as control program 122 according to the present embodiment. The control device 101 reads the control program 122 from the storage device 120 to the ROM 102 based on the reception of the execution instruction of the control program 122. The RAM 103 functions as a working memory, and temporarily stores various data necessary for executing the control program 122.

  An antenna (not shown) and the like are connected to the network interface 104. The image forming apparatus 100 exchanges data with an external communication device via an antenna. The external communication device includes, for example, a mobile communication terminal such as a smartphone, a server, and the like. The image forming apparatus 100 may be configured so that the control program 122 can be downloaded from a server via an antenna.

  The operation panel 107 includes a display and a touch panel. The display and the touch panel are overlaid on each other, and operation panel 107 receives, for example, a printing operation, a scanning operation, and the like for image forming apparatus 100.

  The humidity sensor 108 is provided inside the image forming apparatus 100, and detects the absolute humidity inside the image forming apparatus 100. Preferably, the humidity sensor 108 is provided near the nip between the photoconductor 10 and the charging roller 12.

  The storage device 120 is, for example, a storage medium such as a hard disk or an external storage device. Storage device 120 stores control program 122 and the like according to the present embodiment. The storage location of the control program 122 is not limited to the storage device 120. The control program 122 is stored in a storage area (for example, a cache) of the control device 101, the ROM 102, the RAM 103, an external device (for example, a server), and the like. Is also good.

  The control program 122 may be provided as a part of an arbitrary program, not as a single program. In this case, the control processing according to the present embodiment is realized in cooperation with an arbitrary program. Even a program that does not include such some modules does not depart from the gist of the control program 122 according to the present embodiment. Further, some or all of the functions provided by the control program 122 may be realized by dedicated hardware. Further, the image forming apparatus 100 may be configured in a form such as a so-called cloud service in which at least one server executes a part of the processing of the control program 122.

[Summary]
As described above, the image forming apparatus 100 detects the intermediate density portion in the input image to be printed, and reduces the idle speed of the photoconductor 10 as the area of the intermediate density portion decreases. When the intermediate density portion is small, no band-like noise is generated, so that the image forming apparatus 100 can reduce the number of idle rotations of the photoconductor 10. As a result, the image forming apparatus 100 can delay the pace at which the photoconductor 10 is worn while suppressing a decrease in print quality.

  The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1C, 1K, 1M, 1Y image forming unit, 10 photoconductor, 11 charging device, 12 charging roller, 13 exposure device, 14 developing device, 15 developing roller, 15C, 15K, 15M, 15Y toner bottle, 17, 42 cleaning device , 30 intermediate transfer belt, 31 primary transfer roller, 33 secondary transfer roller, 37 cassette, 38 driven roller, 39 drive roller, 40 timing roller, 41 transport path, 48 tray, 50 fixing device, 60 image, 60A, 60B, 60N, 62A, 62B, 62N area, 61A, 61B, 61C output image, 70 pressing mechanism, 71 toner image, 72 image portion, 73A, 73D nip adjacent area, 80, 82, 84, 86, 88 experimental result, 100 images Forming device, 101 Control device, 102 R M, 103 RAM, 104 network interface, 107 operation panel, 108 a humidity sensor, 120 memory, 122 control program.

Claims (11)

An image forming apparatus having a printing function,
A photoreceptor,
A charging roller that is in contact with the photoconductor and charges the photoconductor,
An exposure device for forming an electrostatic latent image according to an input image on the photoconductor charged by the charging roller,
A developing device for developing the electrostatic latent image formed on the photoconductor,
A control device for controlling the rotation of the photoconductor,
The rotation speed of the photoconductor before the start of printing is predetermined as a default rotation speed,
The control device detects, in the input image, an intermediate density portion in which a pixel value belongs to a predetermined range.If the area of the intermediate density portion is smaller than a predetermined value , the control device rotates the photoconductor before starting printing. If the area of the intermediate density portion is equal to or larger than the predetermined value, the default rotation speed is reduced as the area of the intermediate density portion decreases . The control device detects an area of the intermediate density portion for each of the input images that can be printed when the photoconductor is temporarily rotated by the default rotation speed when receiving a print instruction for a plurality of input images. The image forming apparatus according to claim 1 , wherein when all of the detected areas are smaller than the predetermined value, the rotation of the photoconductor before starting printing is not performed. When the input image in which the area of the intermediate density portion is smaller than the predetermined value is continuous from the first sheet of printing, the control device controls the photosensitive member necessary to print the continuous input image. It calculates the rotational speed, the executing the rotation of the photosensitive member from the default speed for only before starting printing amount corresponding to the difference of the rotary speed, the image forming apparatus according to claim 1 or 2. The developing device develops the electrostatic latent image formed on the photoconductor as a toner image,
The control device includes:
Specifying an image portion corresponding to the intermediate density portion from the toner image,
Determine whether the adjacent area of the nip portion between the photoreceptor and the charging roller before printing starts hits the image portion after printing starts,
When the image portion is determined not impinge on the neighboring region does not perform the rotation of the photosensitive member before the start of printing, the image forming apparatus according to any one of claims 1-3. When the control device determines that the image portion hits the adjacent region, the controller rotates the photoconductor so that the image portion does not hit the adjacent region, and then places the toner image on the photoconductor. The image forming apparatus according to claim 4, which forms the image. The control device, the greater the pixel value in the input image, the reducing the rotational speed of the photosensitive member before the start of printing, the image forming apparatus according to any one of claims 1-5. The control device according to any one of claims 1 to 6 , wherein the shorter the time from the end of the previous printing to the start of the current printing, the smaller the rotation speed of the photoconductor before the start of printing. Item 10. The image forming apparatus according to item 1. The image forming apparatus according to any one of claims 1 to 7 , wherein the control device reduces the number of rotations of the photoconductor before starting printing as the number of prints in a past fixed period decreases. The image forming apparatus further includes a sensor for detecting humidity inside the image forming apparatus,
The image forming apparatus according to any one of claims 1 to 8 , wherein the controller reduces the number of rotations of the photoconductor before starting printing as the humidity detected by the sensor is smaller. A method for controlling an image forming apparatus having a printing function,
The image forming apparatus includes:
A photoreceptor,
A charging roller that is in contact with the photoconductor and charges the photoconductor,
An exposure device for forming an electrostatic latent image according to an input image on the photoconductor charged by the charging roller,
A developing device for developing the electrostatic latent image formed on the photoconductor,
The rotation speed of the photoconductor before the start of printing is predetermined as a default rotation speed,
The control method includes:
Detecting, in the input image, an intermediate density portion whose pixel value belongs to a predetermined range;
If the area of the intermediate density portion is smaller than a predetermined value, the rotation of the photoconductor before starting printing is not performed, and if the area of the intermediate density portion is equal to or larger than the predetermined value, the rotation of the intermediate density portion is Lowering the default rotation speed as the area is smaller. A control program for an image forming apparatus having a printing function,
The image forming apparatus includes:
A photoreceptor,
A charging roller that is in contact with the photoconductor and charges the photoconductor,
An exposure device for forming an electrostatic latent image according to an input image on the photoconductor charged by the charging roller,
A developing device for developing the electrostatic latent image formed on the photoconductor,
The rotation speed of the photoconductor before the start of printing is predetermined as a default rotation speed,
The control program includes:
Detecting, in the input image, an intermediate density portion whose pixel value belongs to a predetermined range;
If the area of the intermediate density portion is smaller than a predetermined value, the rotation of the photoconductor before starting printing is not performed, and if the area of the intermediate density portion is equal to or larger than the predetermined value, the rotation of the intermediate density portion is Lowering the default rotation speed as the area is smaller.