JP2010060807A - Controller for image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller for an image forming apparatus that can appropriately correct density. <P>SOLUTION: The controller for the image forming apparatus includes: a density measuring means 401 for measuring density characteristics of a plurality of images for density measurement 501 formed in a predetermined area according to a plurality of kinds of input density; a storage means 403 for storing a plurality of correction density patterns Y1 to Y6 for a standard density pattern X; an arithmetic calculation means 402 for calculating deviation &Delta;D between the density characteristic measured by the density measuring means and standard density characteristic corresponding to the measured density characteristic; and a selection means 404 for selecting the optimum correction density pattern from the plurality of correction density patterns based on the deviation calculated by the arithmetic calculation means. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a control device used in an image forming apparatus such as a printer, a copying machine, and a facsimile.

  Corrects changes in the output image due to changes in the environment such as temperature and humidity, and changes in the visible image due to deterioration of consumables such as photosensitive drums and toner cartridges in the case of electrophotographic printers. In order to provide a printed image, printing apparatuses that perform density control have been proposed (Patent Documents 1 and 2).

  These printing apparatuses measure the density of a patch actually printed at a predetermined density (patch, a small area filled with a predetermined pattern in order to detect the density by a sensor; hereinafter also referred to as a density measurement image). The actual density output value is corrected based on the difference between the target density and the measured density.

JP 2000-318276 A JP 2008-116806 A

  However, since the number of patch measurement points is small, there is a problem that density measurement values vary and appropriate density correction cannot be performed.

  An object of the present invention is to provide a control device for an image forming apparatus that can appropriately correct the density.

  The control device of the image forming apparatus according to the present invention measures the density characteristic of the density measurement image formed in the predetermined area, calculates the deviation amount between the density characteristic and the standard density characteristic, and based on the deviation amount. The above problem is solved by selecting an optimal (one) correction density pattern from a plurality of correction density patterns stored in advance.

  According to the above invention, the density can be appropriately corrected even if the number of density measurement images is small.

  Hereinafter, embodiments of the invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of a double-sided color printing apparatus according to the present embodiment. The double-sided color printing apparatus 1 according to the present embodiment forms a predetermined image on the first surface 100a (for example, the back surface) of a sheet-like print medium 100 made of continuous paper continuously supplied from a sheet feeding device (not shown). A first printing device 111 for forming a predetermined image on the second surface 100b (for example, the front surface) of the sheet-like print medium 100, and the first surface 100a and the first surface of the print medium 100. And a fixing unit 240 for fixing the toner transferred to each of the two surfaces 100b.

The first printing device 111 and the second printing device 211 are formed by transferring a plurality of color toner images developed in accordance with an electrophotographic method onto the printing medium 100. The toner images are temporarily formed on the first intermediate transfer belt 114 and It is formed on each image forming surface of the second intermediate transfer belt 214. Each of the first intermediate transfer belt 114 and the second intermediate transfer belt 214 is formed of an endless synthetic resin film or the like, and circulates through paths determined by the first belt drive unit 116 and the second belt drive unit 216, respectively.

After the toner images formed on the first intermediate transfer belt 114 and the second intermediate transfer belt 214 are transferred to the front and back surfaces of the print medium 100, the print medium 100 is sent to the fixing unit 240 and heated. As a result, the toner image is fixed on the print medium 100.

  The first intermediate transfer belt 114 is configured to circulate through a circulation path that is formed by the belt driving unit 116 and extends in the up-down direction, in other words, a path that extends toward the first surface 100 a of the print medium 100. Has been. Further, image forming units 120a to 120d for forming toner images are arranged in a predetermined number of colors along at least the side extending in the vertical direction of the circulation path. In FIG. 1, details of the image forming units 120a to 120d are omitted.

FIG. 2 is a detailed view showing one of the image forming units 120a to 120d of this example, and units having the same configuration for each of the four colors of yellow (Y), magenta (M), cyan (C), and black (K). However, the present invention is not limited to this, but it is intended to obtain a color image of a color closer to the request. For example, five or more colors including a specific color may be used, or one color may be used.

  As shown in FIG. 2, the image forming unit 120 includes a photosensitive drum 1201 that is in contact with the first intermediate transfer belt 114, a primary charger 1202 that charges the surface of the photosensitive drum 1201, and a surface on the surface of the photosensitive drum 1201 by an optical unit. The image forming apparatus includes a print head 1203 for forming an electrostatic latent image and a developing device 1205 in which toner 1206 for developing the electrostatic latent image is accommodated. The toner 1206 adheres to the photosensitive drum 1201 by the developing roller 1204, and the toner image Form.

These multi-color image forming units 120a to 120d are arranged side by side on the side of the circulation path of the first intermediate transfer belt 114, and the toner images formed on the photosensitive drums 1201 of the image forming units 120a to 120d are By applying a voltage having a reverse characteristic to that of the toner image, primary transfer is sequentially performed from the photosensitive drum 1201 onto the first intermediate transfer belt 114. This color image can be formed by overlapping a plurality of color toners on the first intermediate transfer belt 114 as necessary.

  In the present embodiment, a first transfer unit 130 is provided above the circulation path of the first intermediate transfer belt 114, and a plurality of colors on the first intermediate transfer belt 114 are applied by applying a bias having a reverse characteristic to the toner image. The toner image is secondarily transferred to the first surface 100 a of the supplied print medium 100.

  On the other hand, the second intermediate transfer belt 214 circulates in a circulation path having a shape extending in the vertical direction formed by the belt driving unit 216, in other words, a path having a shape extending opposite to the second surface 100 b of the print medium 100. It is configured. In addition, image forming units 220a to 220d for forming toner images are arranged in a plurality of predetermined colors along at least the side extending in the vertical direction of the circulation path. In FIG. 1, details of the image forming units 220a to 220d are omitted.

  The image forming units 220a to 220d in this example are provided with four colors of yellow (Y), magenta (M), cyan (C), and black (K), as in the first printing apparatus 111 described above, and more demanding. Although it is supposed to obtain a color image of a close color, it is not limited to this. For example, five or more colors including a specific color may be used, or one color may be used. The configurations of these multi-color image forming units 220a to 220d are the same as those of the unit 120 of the first printing apparatus 111 shown in FIG. 2 except that they are symmetrical with respect to the second intermediate transfer belt 214.

  The image forming units 220a to 220d are arranged side by side on the side of the circulation path of the second intermediate transfer belt 214, and the toner images formed on the photosensitive drums of the image forming units 220a to 220d are the toner images. By applying a voltage having a reverse characteristic, primary transfer is sequentially performed on the second intermediate transfer belt 214 from the photosensitive drum. This color image can be formed by overlapping a plurality of color toners on the second intermediate transfer belt 214 as necessary.

  In the present embodiment, a second transfer unit 230 is provided below the circulation path of the second intermediate transfer belt 214, and a plurality of biases on the second intermediate transfer belt 214 are applied by applying a bias having a reverse characteristic to the toner image. The color toner image is secondarily transferred to the second surface 100 b of the supplied print medium 100.

  FIG. 3 is a block diagram showing a main part of the control device of the printing apparatus 1, and FIG. 5 is a flowchart showing a processing procedure of the control device. The target print data is sent from the control device (not shown) to the print head 1203, whereby a toner image corresponding to the target print image is formed on the photosensitive drum 1201.

  On the other hand, in the printing apparatus 1 of this example, a print command is output from the density measurement image formation instruction unit 301 to the print heads 1203 of the image forming units 120a to 120d and 220a to 220d, and the first intermediate transfer belt 114 and the second intermediate transfer belt 114 are output. A density measurement image 501 shown in FIG. 4 is formed in a drawing area where the toner on the intermediate transfer belt 214 can be visualized and other than the drawing area of the target print image, for example, at both ends of the belts 114 and 214. (Step S1 in FIG. 5).

  FIG. 4 is a diagram showing the density measurement image 501 of this example. In this example, for each of the four colors of yellow (Y), magenta (M), cyan (C), and black (K), the input density (density set in the print data by the user) is 0.25, 0.5, A total of 16 rectangular patterns of 0.75 and 1.0 are used as the density measurement image 501.

  Further, as shown in FIG. 1, a density measuring sensor is located on the transfer surface side of the first intermediate transfer belt 114 and at a position where a final image is formed, for example, between the first transfer unit 130 and the final image forming unit 120a. 401a is provided. The density measurement sensor 401a measures the density of each density measurement image 501 by the toner image formed on the first intermediate transfer belt 114 (that is, the print image on the first surface 100a of the print medium 100), and shifts the density. It outputs to the quantity calculating part 402 (step S2 of FIG. 5).

  Similarly, a density measurement sensor 401b is provided on the transfer surface side of the second intermediate transfer belt 214 where the final image is formed, for example, between the second transfer unit 230 and the final image forming unit 220a. Yes. The density measurement sensor 401b measures the density of each density measurement image 501 by the toner image formed on the second intermediate transfer belt 214 (that is, the print image on the second surface 100b of the print medium 100), and shifts this. It outputs to the quantity calculating part 402 (step S2 of FIG. 5).

  As the density measurement sensor 401, an optical sensor that measures the amount of specularly reflected light or irregularly reflected light can be used.

  The deviation amount calculation unit 402 and the correction density pattern selection unit 404 shown in FIG. 3 are configured by a processor such as a CPU or MPU or hardware logic, and the storage unit 403 is configured by a storage medium such as a memory.

  The deviation amount calculation unit 402 calculates the deviation amount between the density of each density measurement image 501 measured by the density measurement sensor 401 and the standard density. FIG. 6 is a graph showing the relationship of the output density to the input density, and the straight line X is an ideal relational expression in which the output density is equal to the input density. This is called the standard concentration.

  On the other hand, if the actual density measured by the density measuring sensor 401 is the four points A1, A2, A3, and A4 shown in FIG. , 0.75, and 1.0, the differences ΔD1, ΔD2, ΔD3, and ΔD4 between the measured values A1, A2, A3, and A4 and the standard concentration are calculated, and the sum is calculated (step S3 in FIG. 5). ). At this time, in the example of the figure, the measured values A1, A2 and A3 are larger than the standard concentration, and the measured value A4 is smaller than the standard concentration. Therefore, the sum S is S = ΔD1 + ΔD2 + ΔD3-ΔD4. That is, when the measured value is larger than the standard concentration, the sum is calculated with a positive value, and when the measured value is smaller, the negative value.

  The correction density pattern shown in FIG. 7 is mapped and stored in the storage unit 403 in FIG. FIG. 7 is a graph showing the relationship of the corrected output density with respect to the input density.

  The output density of the image that is actually output relative to the input density set in the print data by the user is affected by image forming parameters such as charging potential, exposure intensity, development bias potential, transfer voltage, and toner replenishment amount. In addition to this, the temperature of the developing roller 1204 of the image forming units 120 and 220 is also affected. For this reason, the temperature of the developing roller 1204 varies depending on various conditions such as the initial stage of the printing operation, the duration of the printing operation, and the like, and as a result, the actual output density varies. It has been found by the present inventors that the variation in output density is particularly remarkable in a region where the density is low.

  Therefore, such variations in output density are classified into some patterns in advance, and these are stored in the storage unit 403 as correction density patterns Y1 to Y6. In the six correction density patterns Y1 to Y6 shown in FIG. 7, the pattern Y3 is printed most darkly with respect to the standard density X, and the pattern Y6 is printed lightest with respect to the standard density X. .

  The correction density pattern selection unit 404 in FIG. 3 compares the total deviation S calculated by the deviation amount calculation unit 402 with the total deviation amount with respect to the standard density X of each correction density pattern Y1 to Y6. A close correction density pattern is selected as the optimum pattern (step S4 in FIG. 5). In the example shown in FIG. 7, since the sum of the deviation amounts of the correction density pattern Y1 and the standard density X is equal to the sum S of deviation amounts calculated by the deviation amount calculation unit 402, the correction density pattern Y1 is the optimum pattern. Select as.

  Note that the method of selecting the optimum pattern is not limited to the comparison of the sum of the shift amounts, and a pattern having the closest average value of the shift amounts can also be selected. Further, considering the fact that the output density fluctuation is remarkable in the area where the density is small (thin) as described above, the four measurement points (0.25, 0.5, 0.75, 1.0) It is also possible to compare only the amount of deviation at a specific measurement point such as 0.25 or 0.25 and 0.5.

  When the optimum pattern Y1 is selected by the correction density pattern selection unit 404, the print data is corrected so as to be printed at a correction density corresponding to the correction density pattern Y1. In place of the print data correction process, image forming parameters such as charging potential, exposure intensity, developing bias potential, transfer voltage, and toner replenishment amount can be corrected. More specifically, when the correction density pattern Y1 shown in FIG. 7 is selected, a pattern Y1 ′ obtained by symmetrically moving the pattern with respect to the standard density X as shown in FIG. Print control is executed using the output density as an output density pattern for the input density (step S5 in FIG. 5). The above density correction processing can be executed independently for each of the image forming units 120a to 120d of the first printing apparatus 111 and each of the image forming units 220a to 220d of the second printing apparatus 211.

  As described above, according to the control device of the printing apparatus 1 of the present example, an appropriate correction density pattern can be selected only by performing a simple deviation amount calculation even if there are as few as four density measurement points. it can. Therefore, even if there are few measurement points on the density measurement image 501, it is possible to print at an appropriately corrected density.

It is a schematic block diagram which shows the double-sided color printing apparatus which concerns on embodiment of invention. FIG. 2 is a detailed view showing one of the image forming units in FIG. 1. It is a block diagram which shows the principal part of the control apparatus used for the printing apparatus of FIG. FIG. 4 is a diagram illustrating an example of a density measurement image formed by a density measurement image formation instruction unit in FIG. 3. It is a flowchart which shows the process sequence in the control apparatus of FIG. FIG. 4 is a graph showing a relationship of output density with respect to input density for explaining processing of a deviation amount calculation unit in FIG. 3. It is a graph which shows the relationship of the correction output density with respect to the input density memorize | stored in the memory | storage part of FIG. 6 is a graph showing a relationship of corrected output density with respect to input density output to a printing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Double-sided color printing apparatus 111 ... 1st printing apparatus 114 ... 1st intermediate transfer belt 116 ... 1st belt drive unit 120a-120d ... 1st image formation unit 130 ... 1st transfer unit 211 ... 2nd printing apparatus 214 ... 2nd 2 intermediate transfer belt 216 second belt drive units 220a to 220d second image forming unit 230 second transfer unit 240 fixing unit 100 printing medium 100a first surface 100b second surface 120 image forming unit 1201 ... Photosensitive drum 1202 ... Primary charger 1203 ... Print head 1204 ... Developing roller 1205 ... Developer 1206 ... Toner 301 ... Density measurement image formation instruction unit 401 (401a, 401b) ... Density measurement sensor 402 ... Deviation amount calculation unit 403 ... Storage unit 404... Correction density pattern selection unit 501... Density measurement For images

Claims (7)

Density measuring means for measuring density characteristics of a plurality of density measuring images formed in a predetermined area;
Storage means for storing a plurality of correction density patterns with respect to the standard density pattern;
A computing means for computing a deviation amount between the density characteristic measured by the density measuring means and a standard density characteristic corresponding to the measured density characteristic;
A control unit for an image forming apparatus, comprising: a selection unit that selects an optimum correction density pattern from the plurality of correction density patterns based on a shift amount calculated by the calculation unit. The control apparatus for an image forming apparatus according to claim 1.
The selection unit selects a correction density pattern having a smallest difference between a sum of deviation amounts calculated by the calculation unit and a sum of deviation amounts of the plurality of correction density patterns and the standard density pattern. A control device for the image forming apparatus. The control apparatus for an image forming apparatus according to claim 1.
The selection unit selects a correction density pattern in which a difference between an average value of the deviation amounts calculated by the calculation unit and an average value of deviation amounts of the plurality of correction density patterns and the standard density pattern is the smallest. A control apparatus for an image forming apparatus. The control apparatus for an image forming apparatus according to claim 1.
The density measurement image is formed by a plurality of input densities,
The selection unit has a smallest difference between a deviation amount calculated by the calculation unit and a deviation amount between the plurality of correction density patterns and the standard density pattern at a specific input density among the plurality of input densities. A control apparatus for an image forming apparatus, wherein a correction density pattern is selected. The control apparatus for an image forming apparatus according to claim 4.
The selection unit corrects the difference between the sum of the shift amounts calculated by the calculation unit and the sum of the shift amounts of the plurality of correction density patterns and the standard density pattern at a plurality of specific input densities. A control apparatus for an image forming apparatus, wherein a density pattern is selected. The control device according to any one of claims 1 to 5,
In an image forming apparatus having a plurality of image forming means having different image colors,
The image forming apparatus, wherein the control device selects an optimum correction density pattern for each image color. The control device according to any one of claims 1 to 5,
In an image forming apparatus having a plurality of image forming means for forming images on the front and back of an image forming medium,
The image forming apparatus, wherein the control device selects an optimal correction density pattern for each of the front and back sides of the image forming medium.

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