JP2017142434A - Image forming apparatus, control method, and control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can suppress wear of photoreceptors while suppressing a reduction in printing quality.SOLUTION: An image forming apparatus having a printing function comprises: photoreceptors; charging rollers that are in contact with the photoreceptors for charging the photoreceptors; exposure devices for forming electrostatic latent images according to input images on the photoreceptors charged by the charging rollers; developing devices for developing the electrostatic latent images formed on the photoreceptors; and a control device for controlling rotation of the photoreceptors. The control device executes, in the input images, a step of detecting an intermediate density part in which a pixel value falls within a predetermined range (S12), and a step of reducing the number of rotations of the photoreceptors before the start of printing as the area of the detected intermediate density part is smaller (S20).SELECTED DRAWING: Figure 4

Description

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

  An electrophotographic image forming apparatus is widely used. In an electrophotographic image forming apparatus, as a printing process, a process of uniformly charging a photoconductor, a process of exposing the photoconductor to form an electrostatic latent image, and an electrostatic latent image on the photoconductor are converted into toner. A step of developing as an image and a step of transferring the toner image on the photosensitive member to a sheet are executed.

  The process of charging the photoconductor 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 uniformly charges the photoconductor by rotating.

  FIG. 15 is a diagram illustrating the photoconductor 10 and the charging roller 12. When a long time has elapsed since the previous printing, discharge products are generated in the nip adjacent regions A and B adjacent to the nip portion N of the photoreceptor 10 and the charging roller 12. The discharge product has a hygroscopic property and reduces the toner adsorption force 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 band-like noise is generated. A region 60N of the image 60 is a portion corresponding to the nip portion N of the photoconductor 10. A region 60 </ b> A of the image 60 is a portion corresponding to the nip adjacent region A of the photoconductor 10. A 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 material is generated on the photoconductor 10, as shown in the image 60, the toner does not adhere in the regions 60A and 60B. As a result, white belt-like noise appears in the regions 60A and 60B, and black belt-like noise appears in the region 60N. The band-like noise is particularly noticeable under high temperature and high humidity.

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

  Regarding the idling of the photoconductor, Japanese Patent Application Laid-Open No. 2007-316141 (Patent Document 1) discloses an image forming apparatus that performs idling at high temperature and high humidity. More specifically, the image forming apparatus includes a sensor that detects temperature and humidity. The image forming apparatus performs idling of the photosensitive member 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 Document 1 always performs idling of the photosensitive member when the temperature and humidity detected by the sensor are equal to or higher than predetermined values. Since the photoconductor and the charging roller are in contact with each other, the photoconductor is worn as it rotates. For this reason, if the photoconductor rotates idly, the pace at which the photoconductor wears increases, and the life of the photoconductor is shortened. Therefore, an image forming apparatus that can suppress the wear of the photosensitive member due to idling is desired. At this time, it is also desired that the print quality does not deteriorate.

  The present disclosure has been made in order to solve the above-described problems, and an object in one aspect thereof is to provide an image forming apparatus capable of suppressing wear of a photoconductor while suppressing deterioration in print quality. It is to be. An object in another aspect is to provide a control method capable of suppressing the wear of the photoconductor while suppressing a decrease in print quality. Still another object of the present invention is to provide a control program capable of suppressing the wear of the photoconductor while suppressing a decrease in print quality.

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

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

  Preferably, the rotation speed of the photoconductor before the start of printing is determined in advance as a default rotation speed. The control device decreases the default rotational speed as the area of the intermediate density portion is smaller.

  Preferably, when receiving a print instruction for a plurality of input images, the control device sets 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 the area is detected and all of the detected areas are smaller than the predetermined value, the photoconductor is not rotated before the start of printing.

  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 printed sheet, the control device is required to print the continuous input image. The number of rotations of the photoconductor is calculated, and the rotation of the photoconductor before the start of printing is executed by an amount obtained by subtracting the number of rotations from the default rotation number.

  Preferably, the developing device develops the electrostatic latent image formed on the photoreceptor as a toner image. The control device identifies an image portion corresponding to the intermediate density portion from the toner image, and an adjacent region of a nip portion between the photoconductor and the charging roller before starting printing hits the image portion after starting printing. If it is determined that the image portion does not hit the adjacent area, the photosensitive member is not rotated before the start of printing.

  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 the toner image is transferred to the photosensitive region. Form on the body.

  Preferably, as the pixel value in the input image increases, the control device decreases the number of rotations of the photoconductor before starting printing.

  Preferably, the control device decreases 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 decreases the number of rotations of the photoconductor before the start of printing as the number of printed sheets in the past certain period decreases.

  Preferably, the image forming apparatus further includes a sensor for detecting humidity inside the image forming apparatus. The controller 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 is in contact with a photosensitive member, a charging roller for charging the photosensitive member, and an electrostatic charge corresponding to an input image on the photosensitive member 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 photoreceptor. The control method includes a step of detecting an intermediate density portion in which the pixel value is within a predetermined range in the input image, and a step of decreasing the number of rotations of the photoconductor before starting printing as the area of the intermediate density portion is smaller. With.

  According to still another aspect, a control program for an image forming apparatus having a printing function is provided. The image forming apparatus is in contact with a photosensitive member, a charging roller for charging the photosensitive member, and an electrostatic charge corresponding to an input image on the photosensitive member 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 photoreceptor. The control program causes the image forming apparatus to detect an intermediate density portion in which the pixel value is 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 intermediate density portion is. And a step of reducing the number of rotations.

In one aspect, wear of the photoconductor can be suppressed while suppressing deterioration 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 present invention taken in conjunction with the accompanying drawings.

1 is a diagram illustrating an example of an internal structure of an image forming apparatus. It is a figure which shows three output images from which density differs. It is a figure which shows the experimental result for investigating the idling speed of a photoconductor required in order to suppress strip | belt-shaped noise. 3 is a flowchart illustrating processing executed by the image forming apparatus. FIG. 6 is a diagram for explaining a control example 1 of the photoreceptor. FIG. 10 is a diagram for explaining a control example 2 of the photoreceptor. 6 is a flowchart showing a control example 2 of the photoreceptor. FIG. 10 is a diagram for explaining a control example 3 of the photoconductor. 10 is a flowchart illustrating a third control example of the photosensitive member. FIG. 10 is a diagram for explaining a control example 4 of the photoreceptor. FIG. 10 is a diagram for explaining a photoreceptor control example 5; FIG. 10 is a diagram for explaining a photoreceptor control example 6; FIG. 10 is a diagram for explaining a photoreceptor control example 7; 2 is a block diagram illustrating a main hardware configuration of the image forming apparatus. FIG. It is a figure showing a photoconductor and a charging roller. It is a figure which shows the image which the strip | belt-shaped noise has arisen.

  Embodiments according to the present invention will be described below 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 also the same. Therefore, detailed description thereof will not be repeated. Each embodiment and each modified example described below may be selectively combined as appropriate.

<First Embodiment>
[Internal structure of image forming apparatus 100]
An image forming apparatus 100 according to the embodiment will be described with reference to FIG. 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, may be a fax machine, or may be a monochrome printer, a color printer, and a multifunction machine (MFP: Multi-Functional Peripheral).

  The image forming apparatus 100 includes image forming units 1Y, 1M, 1C, and 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 1 </ b> Y receives toner from the toner bottle 15 </ b> Y and forms a yellow (Y) toner image on the photoreceptor 10. The image forming unit 1M receives toner from the toner bottle 15M and forms a magenta (M) toner image on the photoconductor 10. The image forming unit 1 </ b> C receives the supply of toner from the toner bottle 15 </ b> C and forms a cyan (C) toner image on the photoreceptor 10. The image forming unit 1K receives toner from the toner bottle 15K and forms a black (BK) toner image on the photoconductor 10. That is, the photoreceptor 10 is provided to form a toner image of a specific color.

  The image forming units 1Y, 1M, 1C, and 1K are arranged along the intermediate transfer belt 30 in the rotation direction of the intermediate transfer belt 30, respectively. Each of the image forming units 1Y, 1M, 1C, and 1K includes a rotatable photoreceptor 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 accordance with a control signal from the control device 101, and exposes the surface of the photoconductor 10 according to the input image information. That is, the exposure device 13 forms an electrostatic latent image corresponding to the image information of the input image on the photoreceptor 10 charged by the charging device 11. Thereby, an electrostatic latent image corresponding to the input image is formed on the photoreceptor 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 photoreceptor 10, and a toner image corresponding to the electrostatic latent image is developed on the surface of the photoreceptor 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. A transfer voltage having a polarity opposite to that of the toner image is applied to the primary transfer roller 31, whereby the toner image is transferred from the photoreceptor 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 photoreceptor 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 driving 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 conveyed 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.

  A sheet S is set in the cassette 37. The sheets S are sent one by one from the cassette 37 to the secondary transfer roller 33 along the transport path 41 by the timing roller 40. The control device 101 controls the transfer voltage applied to the secondary transfer roller 33 in accordance with the timing at which the paper 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 conveyed. 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 conveyance timing of 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 paper S.

  The fixing device 50 pressurizes and heats the paper S passing through the fixing device 50. As a result, the toner image is fixed on the paper 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 paper S. The collected toner is conveyed by a conveying screw (not shown) and stored in a waste toner container (not shown).

[Control of idling]
With reference to FIG. 2, the 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 with different densities.

  When a long time has elapsed since 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 discharge products are generated, band-like noise is generated in the output image.

  FIG. 2A shows an output image 61A. Band-shaped noise is generated in the output image 61A. The region 62N of the output image 61A is a portion corresponding to the nip portion N of the photoconductor 10. The region 62A of the output image 61A is a portion corresponding to the nip adjacent region A of the photoconductor 10. A 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 belt-like noise appears in the regions 62A and 62B, and black belt-like noise appears in the region 62N. Band-shaped noise appears every 10 circumferences W of the photoreceptor.

  Such belt-like noise is eliminated by idling the photoconductor 10. Here, idling refers to the rotation of the photoconductor 10 before the start of printing before the 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 is high, no band-like noise is generated. Therefore, when an image having a high density is printed, it is not necessary to perform idling 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 the toner image is not formed, no band-like noise is generated. Therefore, when a white image is printed, it is not necessary to perform idling of the photoconductor 10.

  Therefore, when the intermediate density portion is large in the input image, it is not necessary to execute the idling speed. Focusing on this point, the image forming apparatus 100 detects an intermediate density portion in which the pixel value is within a predetermined range (hereinafter, also referred to as “intermediate range”) in the input image to be printed, and the intermediate density portion. The smaller the area is, the smaller the idling speed of the photoreceptor 10 is. As a result, the image forming apparatus 100 can reduce the idling speed 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 the print quality does not deteriorate even if the number of idling of the photoconductor 10 is reduced.

  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 size of each pixel value correlates with the toner adhesion amount. That is, the larger the pixel value of the input image, the higher the toner density at 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 pixels belonging to the intermediate range among the pixels of the input image as an intermediate density portion.

  Thereafter, the control device 101 calculates the area of the intermediate density portion. As an example of a method for 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 controller 101 decreases the idling speed of the photoconductor 10 as the area of the intermediate density portion is smaller. Preferably, the control device 101 does not perform idling of the photoconductor 10 when the calculated area of the intermediate density portion is smaller than a predetermined value. The magnitude of the predetermined value is determined in advance by experiments or the like. Thereby, the wear 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, etc., the intermediate density portion does not exist in the input image. Therefore, the control device 101 determines whether or not the input image is a line image, and if it is determined that the input image is a line image, it is not necessary to perform the idling of the photoreceptor 10. As an example of a line image detection method, the control apparatus 101 detects an edge portion from an input image. When 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-shaped noise is determined in advance 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 number of revolutions, and executes idling of the photoconductor 10 by the adjusted default number of revolutions.

  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 photosensitive member 10 necessary for suppressing the 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 maximum density (2)
Left time before starting printing: 1 hour (3)
Number of printed sheets before starting printing: 20 sheets (4)
“X” in the experimental result 80 indicates that band-like noise appears in the output image. “Δ” in the experimental result 80 indicates that band-like noise appears a little in the output image. “◯” in the experimental result 80 indicates that no band-like noise appears in the output image.

  From the experimental result 80, in order to suppress the band-like noise, it is necessary to execute 24 idling rotations. That is, under the above conditions, if 24 idle rotations are executed before the start of printing, no band-like noise is reliably generated. 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-like noise is generated. Therefore, the control device 101 of the image forming apparatus 100 decreases the default rotation speed as the area of the intermediate density portion of the input image is smaller. As a result, the image forming apparatus 100 can reduce the idling speed while more accurately suppressing a decrease in print quality.

  In the above description, the example in which the default rotational speed is set to 24 has been described. However, the default rotational speed may be set to other than 24. Since the default rotational speed is determined by experiments or the like, it can be set to an arbitrary value.

[Control Structure of Image Forming Apparatus 100]
A control structure of the image forming apparatus 100 will be described with reference to FIG. FIG. 4 is a flowchart showing processing executed by image forming apparatus 100. The processing in FIG. 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 apparatus 101 determines whether a print instruction has been accepted. When control device 101 determines that a print instruction has been received (YES in step S10), control is switched 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 each pixel of the input image, and detects the pixel group as an intermediate density portion.

  In step S14, the control device 101 calculates the area of 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 the intermediate density portion of the input image is smaller than a predetermined value. The magnitude of the predetermined value is determined in advance by experiments or the like. When control device 101 determines that the intermediate density portion of the input image is smaller than the predetermined value (YES in step S20), control is switched to step S50. If not (NO in step S20), control device 101 switches control to step S40.

  In step S <b> 40, the control device 101 performs the idling rotation of the photoconductor 10 by the default rotation number. As described above, the default rotation speed is determined in advance by experiments or the like. The control device 101 prevents band-like noise from occurring in the output image due to the idling 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 idling in step S40. . Therefore, the control device 101 can suppress excessive idling, and as a result, the pace at which the photoconductor 10 is worn can be delayed.

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

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

  A line image refers to an image composed of characters and straight lines. 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 a predetermined value or more. Therefore, band-shaped noise can occur in the intermediate density image.

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

  In FIG. 5, a plurality of input images are arranged in time series. Assume that the image forming apparatus 100 receives print instructions 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 when the photosensitive member 10 is temporarily rotated by the amount corresponding to the default rotation number. In the example of FIG. 5, the default rotation number is N rotations. When one input image can be printed every time the photoconductor 10 is rotated three times, the number of input images that can be printed at the default rotation number 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 rotational speed. The control device 101 determines whether each of the detected areas is smaller than a predetermined value. When the control device 101 determines that all of the detected areas are smaller than the predetermined value, the control device 101 does not perform idling of the photoconductor 10 before starting printing.

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

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

  In FIG. 6, a plurality of input images are arranged in time series. Assume that the image forming apparatus 100 receives print instructions for the plurality of input images. Based on this, the control device 101 of the image forming apparatus 100 determines whether or not the area of the intermediate density portion is smaller than a predetermined value in order from the first printed input image. The control device 101 detects the number of consecutive 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 necessary for printing an input image corresponding to the continuous number. Since no band-like noise is generated in the continuous input image, the control device 101 does not need to perform idling of the photoconductor 10 for the continuous input image. Therefore, the control device 101 performs idling of the photoconductor 10 by an amount corresponding to the difference between the calculated rotation speed and the default rotation speed.

  For example, as shown in FIG. 6, it is assumed that a plurality of line images continue from the first printed sheet. Since band-like noise does not occur in the line image, it is not necessary to perform the idling of the photoconductor 10 for the line image continuous from the first printed sheet. The control device 101 calculates the number of rotations of the photoconductor 10 necessary for printing a continuous line image. The control device 101 performs idling of the photosensitive member 10 before starting printing by an amount obtained by subtracting the calculated rotation number from the default rotation number.

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

  With reference to FIG. 7, the control example 2 of the photoreceptor 10 will be further described. FIG. 7 is a flowchart showing 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. In addition, since the process of step S10, S12, S14, and S50 is as having demonstrated in FIG. 4, it does not repeat about those description.

  In step S20A, the control apparatus 101 determines whether the area of the intermediate density portion is smaller than a predetermined value in all input images to be printed. When it is determined that the area of the intermediate density portion is smaller than the predetermined value in all input images to be printed (YES in step S20A), control device 101 switches control to step S50. If not (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 printed input image is smaller than a predetermined value. When the control device 101 determines that the intermediate density portion of the first printed input image is smaller than a predetermined value, the control device 101 determines that the first printed input image is a line image or a white image. When the control device 101 determines that the input image for the first print is a line image or a white image (YES in step S30), the control device 101 switches the control to step S40. If not (NO in step S30), control device 101 switches control to step S32.

  In step S <b> 32, the control device 101 detects how many white images and line images are continuous from the first printed sheet. 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 number calculated in step S32 from the default rotation number. That is, the control device 101 reduces the default rotational speed by the rotational speed calculated in step S32.

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

(Control example 3 of idling)
A control example 3 of idling of the photoconductor 10 will be described with reference to FIG. FIG. 8 is a diagram for explaining a control example 3 of the photoconductor 10.

  FIG. 8 shows a toner image 71 formed on the photoreceptor 10. The toner image 71 is formed according to the image pattern in the 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.

  Further, FIG. 8 shows the nip adjacent regions 73A to 73D. The nip adjacent regions 73 </ b> A to 73 </ b> D correspond to regions adjacent to the nip portion between the photoconductor 10 and the charging roller 12 before starting printing. When printing is started, if the image portion 72 hits the nip adjacent regions 73A to 73D, 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, in the image forming apparatus 100, when the image portion 72 hits the nip adjacent regions 73A to 73D, the photosensitive member 10 before starting printing so that the image portion 72 does not hit the nip adjacent regions 73A to 73D. Shift the rotation.

  As a more specific process, the control device 101 of the image forming apparatus 100 specifies an image portion 72 corresponding to the intermediate density portion of the input image from the toner image 71. Thereafter, the control device 101 specifies the 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 areas 73A to 73D before starting printing hit the image portion 72 after starting printing. When the control device 101 determines that the image portion 72 does not hit the nip adjacent regions 73A to 73D, the control device 101 does not perform the idling of the photoconductor 10 before starting printing. This is because when the image portion 72 does not hit the nip adjacent regions 73A to 73D, no band-like noise is generated in the output image. By suppressing excessive idling, 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 suppress the number of idling times of the photoconductor 10.

  With reference to FIG. 9, the control example 3 of the photoreceptor 10 will be further described. FIG. 9 is a flowchart showing a control example 3 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. Since processes other than steps S22, S24, and S26 are as described with reference to FIG. 4, their description will not be repeated.

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

  In step S <b> 24, the control device 101 determines whether or not the photoconductor 10 can be rotated so that the intermediate density portion of the input image does not hit the nip adjacent region. 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 region. . 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 region (YES in step S24), the control is switched to step S26. If not (NO in step S24), control device 101 switches control to step S40.

  In step S <b> 26, the control device 101 rotates the photoconductor 10 so that the intermediate density portion of the input image does not hit the nip adjacent region. Thereby, the control device 101 can reduce the idling speed of the photoconductor 10 even when the intermediate density portion is included in the input image.

(Example 4 of idling control)
With reference to FIG. 10, a control example 4 of idling 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 the 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 occurs and the idling speed. The experiment was performed under the following conditions (5) to (7).

Absolute humidity: 26 (temperature 30 ° C., humidity 85%) (5)
Left time before starting printing: 1 hour (6)
Number of printed sheets before starting 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. “X” in the experimental result 82 indicates that band-like noise appears in the output image. “Δ” in the experimental result 82 indicates that band-like noise appears a little in the output image. “◯” in the experimental result 82 indicates that no band-like noise appears in the output image.

  As shown in the experimental result 82, the higher the image density, the smaller the idling speed. This is because the difference in contrast decreases as the image density increases. Focusing on this point, the control device 101 of the image forming apparatus 100 decreases the idling speed of the photoconductor 10 before starting printing as the pixel value in the input image increases. The pixel value in the input image correlates with the 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 greater than 50% and 75% or less, 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 50% or less, 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 rotational speed to 24 times.

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

  FIG. 11 shows the experimental result 84. The experimental result 84 is a result of investigating the relationship between the leaving time of the photoconductor 10 where no belt-like noise is generated and the idling 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 leaving time indicated in the experimental result 84 is the time from the end of the previous printing to the start of the current printing. In other words, the standing time shown in the experimental result 84 represents the time from when the photosensitive member 10 is stopped until the rotation of the photosensitive member 10 is started next. “X” in the experimental result 84 indicates that band-like noise appears in the output image. “Δ” in the experimental result 84 indicates that band-like noise appears a little in the output image. “◯” in the experimental result 84 indicates that no band-like noise appears in the output image.

  As shown in the experimental result 84, the idling speed may be smaller as the time for which the photosensitive member 10 is left is shorter. This is because the amount of discharge products generated on the photoconductor 10 decreases as the time for which the photoconductor 10 is left is shorter. Focusing on this point, the control device 101 of the image forming apparatus 100 prints as the time from the end of the previous printing to the start of the current printing (that is, the time for which the photoconductor 10 is left) is shorter. 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 the time based on receiving a new print instruction. The control device 101 detects the time count result as the time for which the photoconductor 10 is left.

  As an example, when the exposure time of the photoconductor 10 is 10 minutes or less, the image forming apparatus 100 sets the default rotation speed to zero. When the time for which the photoreceptor 10 is left is longer than 10 minutes and shorter than 1 hour, the image forming apparatus 100 sets the default rotational speed to 24 times. When the time for which the photoreceptor 10 is left is longer than 1 hour and not longer than 24 hours, the image forming apparatus 100 sets the default rotational speed to 28 times. When the time for which the photosensitive member 10 is left is longer than 24 hours, the image forming apparatus 100 sets the default rotational speed to 32 times.

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

  FIG. 12 shows the experimental result 86. The experimental result 86 is a result of examining the relationship between the previous number of printed sheets and the idling number of rotations in which no band-like 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)
Leaving time before starting printing: 1 hour (13)
The number of printed sheets in the past certain period shown in the experimental result 86 indicates the number of input images printed in the past certain period (for example, 1 hour) from the time of the current printing. “X” in the experimental result 86 indicates that band-like noise appears in the output image. “Δ” in the experimental result 86 indicates that band-like noise appears a little in the output image. “◯” in the experimental result 86 indicates that no band-like noise appears in the output image.

  As shown in the experimental result 86, the smaller the number of printed sheets in the past certain period, the smaller the idling speed. This is because the smaller the number of printed sheets in a certain past period, the smaller the amount of discharge products generated on the photoreceptor 10. Focusing on this point, the control device 101 of the image forming apparatus 100 decreases the number of idle rotations of the photoconductor 10 before the start of printing as the number of printed sheets in the past certain period decreases.

  As an example, when the number of printed sheets in a certain past period is 20 sheets or less, the image forming apparatus 100 sets the default rotational speed to zero. When the number of printed sheets in the past fixed period is more than 20 sheets and 100 sheets or less, the image forming apparatus 100 sets the default rotation number to 24 times. When the number of printed sheets in the past fixed period is more than 100 sheets and 500 sheets or less, the image forming apparatus 100 sets the default rotation number to 28 times. When the number of printed sheets in the past fixed period is more than 500, the image forming apparatus 100 sets the default rotation number to 32 times.

(Example 7 of idling control)
A control example 7 of idling of the photoconductor 10 will be described with reference to FIG. 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 the result of examining the relationship between the absolute humidity at which no band-like noise occurs and the idling speed. The experiment was performed under the following conditions (14) to (16).

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

  As shown in the experimental result 88, the smaller the absolute humidity, the smaller the idling speed. This is because the smaller the absolute humidity, the smaller the amount of discharge products generated on the photoreceptor 10. Focusing on this point, the control device 101 of the image forming apparatus 100 reduces the idling speed of the photoconductor 10 before starting printing as the humidity detected by the humidity sensor is smaller.

  As an example, when the absolute humidity is “10” or less, the image forming apparatus 100 sets the default rotational speed to zero. When the absolute humidity is greater than “10” and equal to or less than “16”, the image forming apparatus 100 sets the default rotational speed to 16 times. When the absolute humidity is greater than “16” and equal to or less than “26”, the image forming apparatus 100 sets the default rotational speed to 20 times. When 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 the 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. And a humidity sensor 108 and a storage device 120.

  The control device 101 is configured by at least one integrated circuit, for example. 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.

  The control apparatus 101 controls the operation of the image forming apparatus 100 by executing various programs such as the 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 receiving 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) or the like is 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 such 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 overlapped with each other, and the operation panel 107 receives, for example, a printing operation or a scanning operation for the 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 in the vicinity of the nip portion between the photoconductor 10 and the charging roller 12.

  The storage device 120 is 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, ROM 102, RAM 103, an external device (for example, a server), or the like. Also good.

  The control program 122 may be provided by being incorporated in a part of an arbitrary program, not as a single program. In this case, the control process according to the present embodiment is realized in cooperation with an arbitrary program. Even such a program that does not include some modules does not depart from the spirit of the control program 122 according to the present embodiment. Furthermore, some or all of the functions provided by the control program 122 may be realized by dedicated hardware. Furthermore, the image forming apparatus 100 may be configured in the form of 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 decreases the idling speed of the photoconductor 10 as the area of the intermediate density portion decreases. Since the band-like noise is not generated when the intermediate density portion is small, the image forming apparatus 100 can reduce the idling speed 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 embodiment disclosed this time should be considered as illustrative in all points 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 Drive roller, 39 Drive roller, 40 Timing roller, 41 Conveyance 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 image 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 (13)

An image forming apparatus having a printing function,
A photoreceptor,
A charging roller that is in contact with the photoreceptor and for charging the photoreceptor;
An exposure device for forming an electrostatic latent image corresponding to an input image on the photosensitive member charged by the charging roller;
A developing device for developing the electrostatic latent image formed on the photoreceptor;
A control device for controlling the rotation of the photoconductor,
The control device detects an intermediate density portion in which the pixel value is within a predetermined range in the input image, and the smaller the area of the intermediate density portion is, the smaller the number of rotations of the photoconductor before starting printing is. apparatus.   The image forming apparatus according to claim 1, wherein the control device does not execute rotation of the photoconductor before starting printing when an area of the intermediate density portion is smaller than a predetermined value. The rotational speed of the photoconductor before the start of printing is predetermined as a default rotational speed,
The image forming apparatus according to claim 2, wherein the control device decreases the default rotational speed as the area of the intermediate density portion is smaller.   When the control device receives print instructions for a plurality of input images, the control device detects the area of the intermediate density portion for each of the input images that can be printed when the photoconductor is temporarily rotated by the number of default rotations. The image forming apparatus according to claim 3, wherein the rotation of the photoconductor before the start of printing is not executed when all of the detected areas are smaller than the predetermined value.   When the input image in which the area of the intermediate density portion is smaller than the predetermined value is continuous from the first printed sheet, the control device is configured to print the continuous input image. 5. The image forming apparatus according to claim 3, wherein a rotation speed is calculated, and the photoconductor is rotated before printing is started by an amount obtained by subtracting the rotation speed from the default rotation speed. The developing device develops the electrostatic latent image formed on the photoreceptor as a toner image,
The controller is
Identifying an image portion corresponding to the intermediate density portion from the toner image;
Determining whether an adjacent region of a nip portion between the photosensitive member and the charging roller before starting printing hits the image portion after starting printing;
The image forming apparatus according to claim 1, wherein when it is determined that the image portion does not hit the adjacent area, the rotation of the photoconductor before starting printing is not executed.   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 puts the toner image on the photoconductor. The image forming apparatus according to claim 6, wherein the image forming apparatus is formed.   The image forming apparatus according to claim 1, wherein the control device decreases the number of rotations of the photoconductor before starting printing as the pixel value in the input image increases.   9. The control device according to claim 1, wherein the number of rotations of the photoconductor before the start of printing decreases as the time from the end of the previous printing to the start of the current printing being shorter. The image forming apparatus described in the item.   10. The image forming apparatus according to claim 1, wherein the control device decreases the number of rotations of the photoconductor before the start of printing as the number of printed sheets in the past certain period decreases. The image forming apparatus further includes a sensor for detecting the humidity inside the image forming apparatus,
11. The image forming apparatus according to claim 1, wherein the controller reduces the number of rotations of the photoconductor before starting printing as the humidity detected by the sensor is smaller. A control method of an image forming apparatus having a printing function,
The image forming apparatus includes:
A photoreceptor,
A charging roller that is in contact with the photoreceptor and for charging the photoreceptor;
An exposure device for forming an electrostatic latent image corresponding to an input image on the photosensitive member charged by the charging roller;
A developing device for developing the electrostatic latent image formed on the photoreceptor,
The control method is:
Detecting an intermediate density portion having a pixel value within a predetermined range in the input image;
And a step of decreasing the number of rotations of the photoconductor before starting printing as the area of the intermediate density portion 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 photoreceptor and for charging the photoreceptor;
An exposure device for forming an electrostatic latent image corresponding to an input image on the photosensitive member charged by the charging roller;
A developing device for developing the electrostatic latent image formed on the photoreceptor,
The control program is stored in the image forming apparatus.
Detecting an intermediate density portion having a pixel value within a predetermined range in the input image;
A control program for executing a step of reducing the number of rotations of the photosensitive member before starting printing as the area of the intermediate density portion is smaller.