JP5119643B2 - Image forming apparatus - Google Patents

Description

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

  An image forming apparatus using an electrophotographic system has a process of developing an electrostatic latent image and transferring it onto a transfer sheet. It interferes with sex. That is, in an image to be formed, the amount of printing per page in the printing width direction (main scanning direction) usually varies and is uneven, and when output requests for similar image data continue. In other words, the amount of toner consumed on the developing roll facing the image carrier of the developing unit corresponds to the variation and deviation of the image data in the main scanning direction. As a result, there is a problem that a difference occurs in the electrostatic attraction force of the toner in the area where the toner is consumed on the developing roll and the area where the toner is not consumed, resulting in a difference in image density. In particular, in a developing system having a magnetic one-component developer that rubs magnetic toner with a charging means such as a blade, the structure that eliminates the toner consumption history on the developing roll is a development system having a two-component developer. Compared to this, there are few effects of image data variation and bias.

  In Patent Document 1, an image density detecting means for detecting an image density of an image formed on an image carrier is provided before an electrostatic latent image is formed by the electrostatic latent image forming means, and detection by the image density detecting means is performed. There has been proposed a technique of forming a predetermined electrostatic latent image and forcibly consuming the developer of the developing device when it is determined that the value is lower than a desired value.

JP 2000-206744 A

An object of the present invention is to provide an image forming apparatus capable of reducing the occurrence of image quality defects such as uneven density and fog.

In order to achieve such an object, an image forming apparatus according to the present invention includes a counting unit that counts the number of lighting times of a plurality of light emitting elements arranged in the main scanning direction of the image carrier, and the plurality of light emitting elements counted by the counting unit. A first light-emitting element having a lighting count value equal to or higher than a lower threshold value of the lighting frequency of the light-emitting element and lower than an upper limit threshold value of the lighting frequency of the light-emitting element , A second light emitting element having a count value of the number of lighting times smaller than the lower limit threshold value of the number of lighting times is detected, and for the detected first light emitting element, the number of lighting times of the first light emitting element is set. A value obtained by subtracting the lower threshold from the count value is divided by a difference obtained by subtracting the lower threshold from the upper threshold to calculate a light emitting element lighting ratio. astigmatism of the by subtracting the first light emitting element Calculating a ratio, with respect to the second light emitting element, corresponding to the non-lighting percentage of the calculating means for the non-lighting percentage of 100%, and the first light emitting element and the second light emitting element Toner Forcibly discharging means for consuming toner by forming an image on a line in the sub-scanning direction of the image carrier corresponding to each of the first light emitting element and the second light emitting element ;

  According to the first aspect of the present invention, unnecessary consumption of developer can be suppressed and occurrence of image quality defects such as image density difference and density unevenness can be suppressed as compared with the case where the present configuration is not provided. Can do.

  Preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows the configuration of the image forming apparatus 1. In the present embodiment, an example in which a light emitting diode (hereinafter referred to as an LED (Light Emitting Diode)) is used as the light emitting element will be described, but the present invention is not limited to this.

  The image forming apparatus 1 includes an operation control unit 10, a lighting control unit 11, an image forming unit 20, an LED head 22, a count unit 13, a count number comparison unit 14, a patch image generation unit 15, a first memory unit 16, and a second memory. The unit 12 and the operation unit 17 are included. Note that the operation control unit 10 and the patch image generation unit 15 correspond to a forced discharge unit.

  The operation control unit 10 controls the image forming operation of the image forming unit 20. Further, image data is acquired from a scanner or another computer, and the operation of the lighting control unit 11 is controlled so that an image based on the acquired image data is formed on the photosensitive drum 21. Further, the patch data generated by the patch image generation unit 15 is acquired, and control is performed so that a patch image based on the patch data is formed on the photosensitive drum 21.

  The first memory unit 16 is a computer-readable storage medium composed of a page memory for developing image data, a CPU working RAM, a flash memory as a non-volatile memory, a magnetic storage medium, etc. Various data and programs used for the processing of the unit 10 are stored.

  The lighting control unit 11 controls lighting and extinguishing of each LED in the LED array formed on the LED head 22.

  The second memory unit 12 is configured by a random access memory, and stores control parameters and the like of each LED used when the lighting control unit 11 controls the lighting of the LED head 22. This control parameter is, for example, data such as a current value passed through each LED, and is obtained by reading light amount correction data stored in a ROM (read only memory) included in each LED head 22.

  In addition to the LED head 22, the image forming unit 20 includes a photosensitive drum 21, a developing unit 23, a transfer roll 25, and the like, and is an apparatus that forms image data on a predetermined sheet 24 as an image.

  The LED head 22 is a component of the image forming unit 20 and emits light for exposing the photosensitive drum 21 from an LED array in which LEDs are arranged in a straight line. This light is condensed by a condensing lens, and a condensing spot is formed on the surface of the photosensitive drum 21.

The developing unit 23 develops the electrostatic latent image formed by the LED head 22 with a developer to form a toner image. FIG. 2 shows the configuration of the developing unit 23. The developing unit 23 includes a developer accommodating portion including an opening 35 having a portion facing the photosensitive drum 21 opened along the rotation axis direction of the drum, and a space for accommodating a predetermined amount of the magnetic one-component developer 40. And a housing 30 formed with the housing 31. On the opening 35 side, a cylindrical developing sleeve 34 that rotates with a part of the opening 35 exposed, and a magnet roll 33 that is installed in a fixed state inside the developing sleeve 34 are provided. It has been.
Further, on the developer accommodating portion 31 side of the housing 30, a developer agitating member 32 that rotates to supply the magnetic one-component developer 40 in the developer accommodating portion 31 to the developing sleeve 34 side while agitating, A pressing blade 36 is provided that is pressed against the outer peripheral surface side of the developing sleeve 34 that is close to the developer stirring member 32.

  Returning to FIG. 1, the transfer roll 25 is a roll for transferring the toner image formed on the photosensitive drum 21 by the developing unit 23 onto a sheet. When the transfer roll 25 comes into contact with the photosensitive drum 21 and a voltage having a polarity opposite to the charging potential of the photosensitive drum 21 is applied to the transfer roll 25, the toner image formed on the photosensitive drum 21 is transferred to the transfer roll 25. And the sheet 24 passing between the photosensitive drum 21 and the photosensitive drum 21.

  The counting unit 13 counts the number of times each LED in the LED array formed on the LED head 22 is turned on. In order to count the number of times of lighting, for example, a method of analyzing image data for one page stored in a page memory included in the first memory unit 16 and counting the number of times of lighting of each LED is suitable. Since the LED head 22 is arranged in parallel to the main scanning direction of the photosensitive drum 21, the number of pixels to be exposed by each LED is counted in the sub-scanning direction of the image.

  The count comparison unit 14 sets the set time H and the threshold value T1, and compares the count number (the number of times of lighting) of the count unit 13 during the set time H with the threshold value T1.

  The patch image generation unit 15 generates a patch image for forcibly consuming toner based on the comparison result of the count number comparison unit 14 and outputs the patch image to the operation control unit 10.

The operation unit 17 includes a keyboard, a touch panel, and the like, and inputs instruction information necessary for the control operation of the image forming apparatus 1.

Note that the operation control unit 10, the lighting control unit 11, the count unit 13, the count number comparison unit 14, and the patch image generation unit 15 illustrated in FIG. 1 can be realized by software control. The configuration of the computer in this case is shown in FIG. The CPU 61 reads the program stored in the ROM 62 shown in FIG. 3 and performs operations according to this program by the CPU 61, thereby realizing the functions of the respective devices. The calculation procedure by the CPU 61 will be described later. Further, the RAM 63 functions as the first memory 16 and the second memory 12, and data of calculation results is written therein. NVRAM (Non Volatile RAM) 64 stores data that needs to be backed up when the power is turned off.
Note that the program stored in the ROM 62 may be read from a recording medium such as a CD-ROM and stored in the NVRAM 64, or the program transmitted via the network may be read via the I / O port 65. It may be received and stored in NVRAM 64.

FIG. 4A shows the relationship between the LED head 22 and the developing sleeve 34 in the main scanning direction. FIG. 4B shows an example of an actually drawn image. 4A and 4B, the width of the LED head 22 in the main scanning direction is slightly wider than the maximum width of the image, and the developing width of the developing sleeve 34 is the width of the LED head 22 in the main scanning direction. More widely configured.

FIG. 4C shows the result of counting the number of times each LED is turned on by the counting unit 13 when the image shown in FIG. 4B is formed.
The image data for one page shown in FIG. 4B is temporarily stored in the page memory of the first memory unit 16, and the count unit 13 analyzes the image data stored in the page memory, for each corresponding LED. The number of pixels is counted for each line in the sub-scanning direction (reference direction). The count value is the number of times each LED is turned on. The count result is stored in the first memory unit 16 by the count unit 13.

  When the number of pixels in the sub-scanning direction of the image shown in FIG. 4B is counted, as shown in FIG. 4C, the LED head 22 for printing a vertical frame extending in the sub-scanning direction in the image frame 50. The number of times the LED is turned on becomes extremely large compared to other LEDs. Therefore, there is a difference in toner consumption on the developing sleeve 34 between the area of the image frame 50 and other areas. For this reason, a difference occurs in the electrostatic attraction force of the toner, and a difference occurs in the image density.

To overcome negative effects of such differences in toner consumption, in the present embodiment, by detecting the area preparative toner consumption is small, forced to consume the toner in this region.
In the toner forcible consumption operation, a patch image for forcibly consuming toner by the patch image generation unit 15 when the number of lighting times counted by the counting unit 13 during the set time H does not exceed the threshold T1. This is realized by generating and outputting to the operation control unit 10.

The set time H and threshold value T1 can be changed according to the applied system, such as the characteristics of the photosensitive drum 21, the type of toner, the characteristics of the developing roll , and various parameter settings. Also, the set time H and the threshold value T1 can be changed depending on the allowable image density difference.

  Also, the timing of creating the patch image is preferably during the printing process in which it is determined whether or not the patch is formed by the count comparison unit 14 and in the inter-image portion between the images to be formed. . Furthermore, the patch image may be formed as early as possible during the printing process.

  Further, if the number of operations for forming a patch image and forcibly consuming toner increases, the operation time affects the end time of the printing process. For this reason, for example, a toner image may be forcibly consumed by forming a patch image at the start of print processing after the cumulative print count exceeds several tens or at the end of the print processing. In this case, it is preferable to set the print processing time for forming these tens of images to the set time H.

The patch shape for forcibly consuming the toner takes into account mechanical variations in the main scanning direction (paper width direction) between the image forming unit 20 and a paper transport unit (not shown) that transports the paper. It is desirable to add 2 mm (ie, 4 mm) to both ends of the maximum paper width. In this embodiment, the LED exposure width corresponding to this width is set.
In the sub-scanning direction, in order to eliminate the difference in toner consumption of the developing roll , it is desirable that the width of the developing sleeve 34 is about (L) +2 mm.

The processing procedure of the present embodiment will be described with reference to the flowchart shown in FIG.
When the printing process is started (step S1 / YES), the number of lighting of the LEDs arranged in the main scanning direction is counted by the counting unit 13 in the sub-scanning direction of the image (step S2). If the execution time of the printing process exceeds the set time (step S3 / YES), the count value of the count unit 13 and the threshold value T1 are compared by the count number comparison unit 14 (step S4). When the count value falls below the threshold value T1 (step S4 / YES), the patch image generation unit 15 forms a patch image at the inter-image portion between the images. The formed patch image is sent to the operation control unit 10. The operation control unit 10 controls the lighting control unit 11 to form an image based on the patch image before or after the start of the printing process, thereby forcibly consuming toner in a region where the toner consumption is small (step S1). S5).

A second embodiment will be described with reference to the accompanying drawings. The configuration of the present embodiment is the same as the configuration of the first embodiment described above, and thus the description of the configuration is omitted.
In order to suppress wasteful toner consumption due to forced toner consumption, it is desirable to correct variations and deviations in the toner consumption amount in the main scanning direction (many areas with low consumption and few areas with high consumption).

  As shown in FIG. 4C, the count unit 13 counts the number of times the LEDs arranged in the main scanning direction are turned on in the sub-scanning direction. Therefore, the patch image generation unit 15 performs sub-proportional to the count data. This is realized if the patch shape is generated so as to have the scanning width.

  Specifically, as shown in FIG. 4D, the ratio A (%) of the actual lighting frequency between the lower threshold value T1 and the upper threshold value T2 is obtained from the total lighting frequency of the difference between the lower threshold value T1 and the upper threshold value T2. This is realized by generating a patch by applying, for each LED dot, a width obtained by multiplying a ratio (100-A)% inversely proportional to L + 2 mm which is a patch reference width in the sub-scanning direction.

  The above-described embodiment is an example of a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.

1 is a diagram illustrating a configuration of an image forming apparatus. It is a figure which shows the structure of a developing device. It is a figure which shows the computer structure for implement | achieving software control. (A) is a figure which shows the relationship of the main scanning direction of an LED head and a developing sleeve, (B) is a figure which shows an example of the image formed, (C) is the lighting frequency for every LED element. (D) is a figure which shows the patch shape which is a sub-scanning width in inverse proportion to the count data for every LED element. 4 is a flowchart illustrating a processing procedure of the operation control unit 10.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Operation control part 11 Lighting control part 12 2nd memory 13 Count part 14 Count number comparison part 15 Patch image generation part 16 1st memory part 20 Image formation part 21 Photosensitive drum 22 LED head 23 Developing unit 24 Paper 25 Transfer roll 30 Housing 31 Developer accommodating portion 32 Developer stirring member 33 Magnet roll 34 Developing sleeve 35 Opening portion 36 Pressure contact blade 40 Magnetic one-component developer

Claims (1)

Counting means for counting the number of times of lighting of the plurality of light emitting elements arranged in the main scanning direction of the image carrier,
Using the count value of the number of times of lighting of the plurality of light emitting elements counted by the counting means, the count value of the number of lighting times is equal to or greater than a lower limit threshold value of the number of lighting times of the light emitting element, a first light emitting element is the value or less, the count value of the number of lighting times detects a smaller second light emitting element than the lower threshold of the number of lighting times, with respect to the first light emitting element detected in The light emitting element lighting ratio is calculated by dividing the value obtained by subtracting the lower threshold from the count value of the number of lighting times of the first light emitting element by the difference obtained by subtracting the lower threshold from the upper threshold. Then, the non-lighting ratio of the first light emitting element is calculated by subtracting the calculated light emitting element lighting ratio from 1 , and the non-lighting ratio is set to 100% for the second light emitting element. When,
A toner image corresponding to a non-lighting ratio between the first light emitting element and the second light emitting element is used as a sub image of the image carrier corresponding to each of the first light emitting element and the second light emitting element. Forcibly discharging means for consuming toner formed on a line in the scanning direction;
An image forming apparatus comprising:

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