JP2017138368A - Image forming system and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration of toner to stably form a high-quality image.SOLUTION: An image forming system 10 comprises a control part 110 that determines the degree of deterioration of a toner inside a developing unit 152 from the consumption of the toner, and controls an image forming part 150 according to the degree of deterioration to form a watermark image W for discharging the toner inside the developing unit 152 in an image forming area on a sheet for forming an image based on a print job.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an image forming system and an image forming method.

  In image forming systems such as copying machines and printers using electrophotography, the electrostatic latent image formed on the photoreceptor is developed by a developing device to form a toner image, which is transferred onto paper and heated. By fixing, an image is formed on the paper surface.

  When the toner is consumed from the developing unit, the toner corresponding to the consumed amount is supplied into the developing unit. Inside the developing device, the replenished toner is mixed with a carrier and stirred in the developing device to give a predetermined charge amount.

  If the consumption amount of the toner is a certain level or more, the toner in the developing device is consumed by the consumption / replenishment cycle, the old toner is consumed, and new toner is replenished. However, when the toner consumption is extremely small, the toner stays in the developing device for a long time, so that the external additive added to the toner surface may be buried in the toner surface due to stress caused by long-time stirring. Due to the separation from the toner surface, the charge of the toner is lowered or the charge distribution becomes broad. With such deteriorated toner, image quality deterioration and toner scattering occur.

  For such problems, as an index for judging the deterioration degree of the toner in the developing device, the image coverage (printing rate) is monitored within a predetermined period, and if the low coverage printing continues, the developing device It is determined that the toner inside is deteriorated. A technique is known in which when a toner deteriorates, a patch image (hereinafter also referred to as “abandoned patch”) is formed and the toner in the developing device is forcibly consumed and replaced with new toner.

  For example, in the image forming apparatus disclosed in Patent Document 1, a toner discharge band image extending in the sheet conveyance direction is formed on both sides of a continuous sheet so that the toner discharge amount is a predetermined amount or more. Yes.

Japanese Patent Laying-Open No. 2015-55673

  However, the image forming apparatus disclosed in Patent Document 1 cannot form an image in an area where band images on both sides are formed, and the entire continuous sheet cannot be used effectively. In addition, it is necessary to cut and discard the band image in a post process, and an extra post process is required.

  Further, in the conventional technology for forming a discard patch, when forming an image on continuous paper, it is necessary to form a discard patch in the middle, and it is necessary to interrupt the print job while the discard patch is formed. And productivity deteriorates. In addition, when continuous paper is cut in a subsequent process, when images are continuously formed at equal intervals, the intervals become discontinuous by discarding patches in the middle, and the same intervals are assumed. Post-processing is affected.

  There is a similar problem with cut paper. For example, when forming continuous images, if discard patches are formed between sheets, patches for image stabilization monitoring are formed between sheets, or if the gap between sheets is smaller than the size of the discard patches In this case, the discard patch cannot be formed at a normal sheet interval. In that case, it is necessary to increase the sheet interval more than usual, and the productivity deteriorates.

  The present invention has been made in view of the above circumstances, and effectively uses the entire surface of a sheet, suppresses toner deterioration without affecting productivity, and stably forms a high-quality image. An object of the present invention is to provide an image forming system and an image forming method that can be used.

  The above object of the present invention is achieved by the following means.

(1) an image forming unit that includes a developing unit that develops, with toner, an electrostatic latent image formed on a photoconductor based on a print job, and forms an image on the sheet by transferring the developed toner to the sheet;
A toner replenishing section for replenishing toner to the developing device;
The degree of deterioration of the toner in the developing device is determined based on the amount of toner consumed, and the image forming unit is controlled according to the degree of deterioration to display a watermark image for discharging the toner in the developing device on a sheet. A control unit that forms an image based on the print job in an image forming area;
An image forming system.

(2) The watermark image has a uniform density over the entire surface, and the control unit determines a discharge amount of toner according to the degree of deterioration, and determines a size of the watermark image according to the discharge amount.
The image forming system according to (1) above.

(3) There are a plurality of the developing units, and each developing unit stores different color toners,
The image forming system according to (1) or (2), wherein the control unit sets a density of the watermark image for each toner color.

(4) Provided with an input unit that accepts user settings,
The image forming system according to any one of (1) to (3), wherein the control unit changes a density of the watermark image based on a density setting received by the input unit.

(5) The control unit determines the degree of deterioration of the toner and determines the discharge amount each time the image formation length reaches a predetermined length as a processing section or each time the developing unit reaches a predetermined operation amount. Run
If the amount of toner discharged when the watermark image is formed in the entire next processing section does not reach the determined amount of discharge, the control unit forms a solid image band to form a toner image. Perform the discharge,
The image forming system according to any one of (1) to (4) above.

(6) When the second image area for forming an effective image is set in a part of the area of the first image area that is an area where image formation is possible on the paper,
The image forming system according to any one of (1) to (5), wherein the control unit forms the watermark image in the first image area excluding the second image area.

(7) When executing the print job, the control unit uniformly distributes the watermark image at the density on the entire image forming area of the paper corresponding to the print job based on the set density of the watermark image. The degree of deterioration of the toner in the developing device is determined when
When forming an image based on the print job, when the control unit determines that the degree of deterioration is equal to or less than a predetermined value, the control unit forms the uniform watermark image at the density on the entire surface of the image forming area of the paper. The image forming system according to 4).

(8) When executing the print job, the control unit determines the degree of deterioration of the toner in the developing device based on the image data of the print job,
When forming an image based on the print job, the control unit causes the uniform watermark image to be formed on the entire surface of the image forming area of the paper according to the determination, and any one of (1) to (6) above The image forming system according to claim 1.

(9) an image forming unit that includes a developing unit that develops the electrostatic latent image formed on the photoreceptor based on the print job with toner, and that forms an image on the sheet by transferring the developed toner to the sheet; An image forming method in an image forming system comprising: a toner replenishing unit that replenishes toner to a developing device;
Determining the degree of deterioration of the toner in the developing device according to the amount of toner consumed;
Controlling the image forming unit in accordance with the degree of deterioration to form a watermark image for discharging the toner in the developing device in an image forming area for forming an image based on the print job on a sheet; ,
An image forming method comprising:

  According to the present invention, the degree of deterioration of the toner in the developing unit is determined, and when the degree of deterioration is equal to or greater than a predetermined value, a watermark image for discharging the toner in the developing unit by controlling the image forming unit is displayed on the sheet. In this way, it is possible to stably form a high-quality image while effectively using the entire surface of the paper and suppressing the deterioration of the toner without affecting the productivity.

1 is a schematic diagram illustrating an overall configuration of an image forming system according to an embodiment of the present invention. 1 is a block diagram illustrating a hardware configuration of an image forming apparatus It is a figure which shows the cut paper on which the image was formed. It is a figure which shows the cut paper on which the image was formed. FIG. 4 is a diagram illustrating a state in which a plurality of print images are printed side by side on a continuous paper, and a watermark image using K toner and Y toner is superimposed on a part of the print images. 3 is a flowchart illustrating an image forming method executed by a control unit. This is a subroutine of step S108 in FIG. It is a figure which shows the arrangement | positioning state of the watermark image on a continuous paper. 5 is a flowchart illustrating an image forming method in a full color mode executed by a control unit. It is a figure which shows the arrangement | positioning state of the watermark image on a continuous paper. It is a figure which shows the arrangement | positioning state of the watermark image on a continuous paper. FIG. 12A is a diagram showing an image forming area excluding margins at both ends of the continuous paper S as a first image forming area, and FIG. 12B is a diagram showing a second image forming area. FIG. 12C shows a watermark image in the second embodiment, and FIG. 12D shows a state in which FIGS. 12A to 12C are superimposed on the continuous paper S. FIG. 10 is a flowchart illustrating an image forming method according to a third embodiment executed by a control unit. It is a figure which shows the state which formed the watermark image on the whole surface of continuous paper.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

  FIG. 1 is a schematic diagram showing a configuration of an image forming system 10 according to a first embodiment to which the present invention is applied. The image forming system 10 includes an image forming apparatus 100, a paper feeding device 200, a paper feeding adjusting device 300, a paper discharging adjusting device 400, and a winding device 500.

  The paper feeding device 200 stores and holds the roll R0 that is the original winding of the continuous paper, and sends the continuous paper S downstream in the paper transport direction.

  The paper feed adjusting device 300 has a buffer function for absorbing a minute paper transport speed difference between the paper feed device 200 and the image forming apparatus 100 and a paper shift.

  The image forming apparatus 100 includes in its main body an image forming unit 150 that forms an image by a known electrophotographic process using toner. The image forming unit 150 includes a photosensitive drum 151, a developing device 152, an intermediate transfer belt 153, a fixing unit 154, and an exposure unit 155 (see FIG. 2). A plurality of photosensitive drums 151 and developing units 152 (reference numerals are only partially described) are provided, and the respective colors Y (yellow), M (magenta), C (cyan), and K (black) are sequentially arranged from the top. It corresponds.

  In each of the developing devices 152, a two-component developer obtained by mixing each color toner and carrier is stored. The electrostatic latent image formed on the surface of the photosensitive drum 151 by the exposure unit 155 is developed by the developing device 152, and a toner image is formed on the surface of the photosensitive drum 151. The toner images formed on the respective photoconductive drums 151 are superimposed on the intermediate transfer belt 153, transferred to the surface of the continuous paper S, and then heated by the fixing unit 154. As a result, a full-color image is formed on the surface of the continuous paper S.

  The toner supply unit 190 stores and conveys toner corresponding to each color. When the toner is consumed in the developing device 152, the toner corresponding to the consumed amount is replenished into the developing device 152 by the toner replenishing unit 190 so as to maintain the toner concentration of the two-component developer composed of carrier and toner. The The replenished toner is charged with a predetermined charge amount by being mixed with the carrier and stirred by the stirring screw inside the developing device 152.

  Similarly to the paper feed adjusting device 300, the paper discharge adjusting device 400 also has a buffer function for absorbing a minute paper transport speed difference between the image forming apparatus 100 and the winding device 500 and a paper shift. The paper discharge adjusting device 400 includes a cutter 401 that cuts the continuous paper S, and can cut the continuous paper S along a width direction orthogonal to the transport direction at a desired position.

  The continuous paper S that has passed through the paper discharge adjusting device 400 reaches the winding device 500 and is wound and held on a roll R1. The continuous paper S may be a label paper in which a label obtained by applying an adhesive to the paper is bonded to a release paper. When label paper is used, the label may be cut out in a size corresponding to the image by the cutter 401. The roll R1 is loaded into the cutting machine in a post-processing step, and the continuous paper S is pulled out from the roll R1 while pulling the continuous paper S. For example, it may be cut out.

  In the example illustrated in FIG. 1, the image forming system 10 that forms an image on the long continuous paper S is illustrated. However, the paper feeding device 200, the paper feeding adjusting device 300, the paper discharging adjusting device 400, and the winding device are illustrated. A configuration including only the image forming apparatus 100 in which 500 is omitted may be used as the image forming system 10. In this case, cut sheets are conveyed to the image forming unit 150 one by one from a paper feed tray provided in the lower part of the image forming apparatus 100 or a large capacity paper feed apparatus connected to the upstream side to form an image.

  FIG. 2 is a block diagram illustrating a hardware configuration of the image forming apparatus 100. The image forming apparatus 100 includes a control unit 110, a print controller unit 120, an operation display unit 130, a scanner 140, an image forming unit 150, and an external device control unit 160. The external device control unit 160 controls the paper feed device 200, the paper feed adjustment device 300, the paper discharge adjustment device 400, and the winding device 500 described above.

  The control unit 110 includes an image control CPU 111, a DRAM control IC 112, a non-volatile memory 113, an image memory 114, an RTC 115, a compression / decompression IC 116, a reading processing unit 117, a writing processing unit 118, and the like.

  The image control CPU 111 develops various programs stored in the non-volatile memory 113 or the HDD (not shown) in the non-volatile memory 113, and controls the overall operation of the image forming system 10 in cooperation with the developed programs. Control. An RTC (Real-Time Clock) 115 functions as a date / time data generator that outputs the current time.

  The reading processing unit 117 performs various processes such as an analog process, an A / D conversion process, and a shading process on the analog image signal output from the CCD of the scanner 140 to generate digital image data. The generated digital image data is output to the compression / decompression IC 116 by the DRAM control IC 112. The compression / decompression IC 116 performs compression processing on the digital image data and decompression processing on the digital image data after the compression processing based on the control of the DRAM control IC 112. The DRAM control IC 112 performs input / output control of the image memory 114 for the compressed / decompressed digital image data.

  The image memory 114 is composed of a DRAM (Dynamic RAM), and includes a compression memory area and a page memory area therein, and temporarily stores compressed image data, decompressed image data, and the like. When image data such as a label image, which will be described later, is repeatedly output, the image data temporarily stored in the image memory is developed in each memory reading module inside the DRMA control IC 112. The memory read module has a repeat function. The repeat function is a function for reading an image developed in such an image memory 114 to a memory module, placing it in an arbitrary position in the main scanning direction (width direction of the continuous paper S), and repeatedly outputting it in the sub-scanning direction. is there. Note that the maximum value of the output in the sub-scanning direction is the upper limit of the counter value (clk number) of the memory module so as to correspond to the feed length (4 to 6 km) of the maximum diameter roll R0 usable in the image forming system 10. A value is set.

  The writing processing unit 118 outputs the decompressed digital image data to the exposure unit 155 of the image forming unit 150.

  The print controller unit 120 includes a controller control unit 121, a DRAM control IC 122, an image memory 123, a communication I / F 124, and the like. The controller control unit 121 comprehensively controls the operation of each unit of the print controller unit 120. Further, the controller control unit 121 receives a print job from a PC or the like via the communication I / F 124. The received print job includes a job ticket in which print settings such as the type of paper to be used are described, and image data (mainly PDL format) that is the basis of the print image. The print controller unit 120 performs rasterization processing for converting image data into bitmap data in units of pages based on print settings. The data after rasterization processing (hereinafter also referred to as “raster image”) temporarily stored in the image memory 123 is compressed and controlled under the control of the DRAM control IC 122 of the print controller unit 120 and the DRAM control IC 112 of the control unit 110. The data is temporarily stored in the compressed memory area in the image memory 114 via the decompression IC 116. During normal printing, the raster image stored in the compression memory area is decompressed by the compression / decompression IC 116 and sent to the image forming unit 150 via the write processing unit 118 to be printed.

  The operation display unit 130 includes an LCD (Liquid Crystal Display) and a touch panel provided with a touch sensor. The operation display unit 130 displays various setting screens and accepts various operations by the user. When receiving an operation from the user, the operation unit control unit generates an operation signal and outputs the generated operation signal to the image control CPU 111.

(Watermark image)
Hereinafter, the watermark image in the present embodiment will be described with reference to FIGS. 3 and 4 are diagrams showing cut sheets formed with the image forming system 10 shown in FIG. 1 and the like. FIG. 3A is an example of a full-color print image G1 formed based on image data included in a print job, and FIG. 3B is an image formation of cut paper using a watermark image W of 5% density K toner. FIG. 3C illustrates an example in which the images in FIGS. 3A and 3B are superimposed (synthesized). 4A is formed by superimposing a watermark image Wk made of K toner having a density of 1% on the print image G1, and FIG. 4B is made by superimposing a watermark image Wy made of Y toner having a density of 5% on the print image G1. FIG. 4C shows an example in which the same image as FIG. 4B is formed on yellow cut paper. Note that white cut paper is used except for FIG. In the figure, for the sake of explanation, the watermark image is shown conspicuously, but in reality, it is difficult for most users to recognize it visually. The watermark image is formed on the entire surface of the image forming area. Here, the “image forming area” is also referred to as a printable area, and excludes edges (for example, 1 mm width outer margin) in the width direction and the front-rear direction of paper (continuous paper and cut paper) due to restrictions on the apparatus side. It is an area.

  FIG. 5 shows a state in which a plurality of print images G2 are printed side by side on the continuous paper S, and a watermark image Wk made of K toner and a watermark image Wy made of Y toner are superimposed on a part of the print images G2. FIG. In the figure, label paper is used as the continuous paper S, and the print image G2 is a label image. The density of the watermark image is 5%.

  In this embodiment, the “watermark image” is a low density that does not affect the visual recognition of an original image (hereinafter also referred to as “print image” or “product image”) formed based on image data of a print job. Thus, the original image is formed so as to be seen through. The maximum density of the watermark image within a range that is not noticeable differs depending on the color difference between the toner color and the paper color and the shape of the watermark image. In general, an image that is uniform over the entire surface of the paper and formed on the basis of the same density signal (gradation signal) for all pixels is most difficult to recognize. In this embodiment, unless otherwise specified, a watermark image is used that is developed with toner on an electrostatic latent image that is uniform over the entire surface of the image forming area of the paper and is formed with a density signal having the same predetermined value for all pixels. .

  In the present embodiment, a preset value is used as this density signal. For example, the density is in the range of 1 to 5% as the set value, and the density signal is in the range of 2/255 (1%) to 13/255 (5%) if it has an 8-bit gradation.

  In general, when the brightness difference from the color of the paper is large, it is easy to visually recognize. Therefore, when normal white paper is used, the same density signal is easily recognized in the order of K, M, C, and Y. For this reason, the density signal of the watermark image may be set to a different density signal for each color, for example, the K density signal is set to a smaller value than the density signals of the other colors. The watermark image density may be set by the user, and the density signal may be changed in accordance with the set density setting. This setting can be performed through the operation display unit 130. For example, when a yellow sheet is used (FIG. 4C), it is difficult to recognize a watermark image with Y toner, so that the Y density signal can be set high. Setting the density signal to a low value makes it difficult for the user to recognize the watermark image, but on the other hand, the toner discharge effect by forming the watermark image described below is reduced.

(Purpose and effect of forming watermark images)
As described above, if the amount of toner consumed from the developing device 152 is equal to or greater than a certain level, new toner is replenished, so that the toner in the developing device 152 can maintain a desired performance. In the present embodiment, in the control (image forming method) described later, the control unit 110 determines the degree of toner deterioration from the amount of toner consumed, specifically, the image coverage of the image data (average coverage within the section). Yes. When the image coverage is equal to or less than the threshold value and the toner consumption amount does not reach the target value, control is performed so that the insufficient amount of toner is consumed by the watermark image. As a result, the deterioration of the toner in the developing device 152 can be suppressed, the toner performance can be maintained above a certain level, and the image quality can be stabilized. Further, in the present embodiment, the toner consumption shortage is not executed by the solid image band formed between both ends of continuous paper or between continuous sheets of cut paper as in the prior art, but on the paper. The watermark image formed in the image forming area is used. By doing so, the entire surface of the continuous paper can be used as an image forming area, and if it is a cut paper, there is no need to widen the paper. Even if an image for discharging the toner is formed in the image forming area on the paper, the image is a watermark image, so that it is difficult for the user to recognize it, and the image quality is not affected.

(Image forming method)
Hereinafter, the image forming method according to the present embodiment will be described with reference to FIGS. 6 and 7 are flowcharts illustrating an image forming method executed by the control unit 110, and FIG. 8 is a diagram illustrating an arrangement state of the watermark image W on the continuous paper S. FIG.

  In FIG. 6, when a print job is started in accordance with a user instruction, it is determined in the first step S101 whether the processing section x (processing period) has elapsed (S101). In this embodiment, a processing section is used as a processing unit for determining the degree of deterioration of toner in the developing device 152. The processing section is a predetermined transport distance (1 m in the example described later) of the continuous paper S during operation of the developing device 152 (during image formation).

  If the processing section x has elapsed (S101: YES), the image coverage Cx in the processing section x is calculated (S102), and the calculated image coverage Cx is compared with the image coverage threshold Ct to form the watermark image W. Is determined (S103).

  If the image coverage Cx is equal to or less than the image coverage threshold Ct (S103: YES), it is determined that a watermark image is to be formed, and then the size of the watermark image is determined (S104). In the next step S105, it is determined whether or not this watermark image can be formed. Specifically, it is determined whether or not the watermark length Lw representing the size of the watermark image W necessary for discharging the toner calculated in step S104 falls within the next processing section x + 1.

  When it is determined that the watermark length Lw is equal to or less than the watermark length threshold Lwt and can be formed in the area of the next processing section x + 1 (S105: YES), the watermark image W is set at a predetermined position in the processing section x + 1, for example, the front end. The reference image is arranged so as to overlap the print image G (S106).

  On the other hand, if it is determined in step S105 that the watermark length Lw is longer than the watermark length threshold Lwt and the watermark image W does not fit in the next processing section x + 1 (S105: NO), in step S108. Create a discard patch. The discarded patch is a band of a solid image (high density close to 100% density).

  FIG. 7 is a diagram showing a subroutine of S108, where FIG. 7A shows processing when an image is formed on continuous paper S, and FIG. 7B shows processing when a cut paper is formed.

  In the case of continuous paper, the discarded patch is formed on the surface of the continuous paper S. In step S201, a band width Wdx, which is the length of the discarded patch in the conveyance direction, is calculated. If the discarded patch is formed at a density of 100%, the above-described short length Lsh can be applied as it is.

  Then, after the job being printed is interrupted, the discarded patch is formed with the band width Wdx (= Lsh) without being superimposed on the normal print image G2, and after the formation, the interrupted print job is resumed ( S202 to S204), the process returns to the process of FIG.

  The same applies to the cut sheet of FIG. The band width Wdx is calculated. If the band width Wdx does not fit within the continuous sheet interval, the sheet interval is increased according to the band width Wdx, and then a discarded patch is formed between the sheets (S301 to S304). Returning to the process of FIG.

  If it is determined that the formation of the watermark image W is unnecessary (S103: NO), or if a watermark image or a discard patch for toner discharge is formed as necessary (S106, S108), a step is performed if the print job continues. The processing from S101 onward is repeated, and when the print job ends, the processing ends (S107, end).

(Specific example of image forming method)
Hereinafter, a specific example will be described. FIG. 8 is a diagram illustrating a state in which a plurality of print images G2 are arranged on the continuous paper S in the same manner as FIG. Note that the size and size of the print image shown in FIG. 8 (the same applies to FIG. 10 and subsequent figures) are displayed for explanation, and do not directly correspond to the numerical value of the image coverage Cx.

Here, each condition in the following specific example is shown.
Image mode: K mono-color printing section distance Lc: 1 m
Image coverage threshold Ct: 5%
Watermark density setting Dws: 2%
Watermark length threshold Lwt: 1m
The section distance Lc, the image coverage threshold value Ct, the watermark density setting Dws, and the watermark length threshold value Lwt are stored in advance in the nonvolatile memory 113. Among these, the watermark density setting Dws can be set by the user. Other settings are predetermined based on the characteristics of the toner. Note that the image coverage threshold Ct is the minimum toner consumption that can maintain a certain level of quality when a continuous image is formed with the image coverage of this threshold. This causes image defects. The image coverage threshold Ct is an index for determining the degree of toner degradation, and may be a different value for each color or may be set to the same value according to the toner characteristics. The watermark length threshold Lwt is set to the same length as the section distance Lc, but may be set shorter than the section distance Lc.

  In FIG. 8, the lengths of the processing sections x to x + n are all set to the same section distance Lc. The control unit 110 calculates the image coverage Cx during one processing section, for example, the processing section x. Then, a watermark image is formed in the next processing section x + 1 according to the determination result of the processing section x. Thereafter, similarly, a watermark image is sequentially formed in the next processing section according to the determination result of the previous processing section.

Here, image coverage Cx = print area in process section x / paper area in process section x, and print area = print pixel area × gradation. For example, when the width of the continuous paper S is 30.2 cm and a margin of 0.1 cm is provided at both ends, the area of the image forming region in the processing section x (100 cm) excluding this is 30 × 100 = 3000 cm ^2. . When an image having a uniform density on the entire surface is formed in this entire image forming area with a gradation of 10/255, the printing area is 117.6 cm ² . Since the sheet area in the processing section x is 30.2 × 100 = 3020 cm ² , the image coverage Cx is about 4%.

(Processing section x)
Image coverage Cx in processing section x = 4%
When the image coverage Cx of the processing section x is 4%, it is determined that the watermark image W is necessary because the image coverage Cx (4%) ≦ the image coverage threshold Ct (5%) (S103: YES). Then, the length Lw of the watermark image is determined from the image coverage Cx (S104).

  When the insufficient toner consumption is defined as insufficient image coverage Csh, insufficient image coverage Csh = image coverage threshold Ct−image coverage Cx = 1%.

  Therefore, the short length Lsh = Lx × Csh = 0.01 m. For example, if a discharge image is formed by a band extending in the width direction of a solid image having a density of 100%, the width is 0.01 m.

  Therefore, the watermark length Lw = Lsh / WDs = 0.01 m / 2% = 0.5 m necessary for discharging the toner. The above is the processing corresponding to steps S102 to S104.

  Next, it is determined whether or not the necessary watermark image W falls within the processing section x + 1. Here, since the watermark length Lw is 0.5 m, which is shorter than 1 m of the watermark length threshold Lwt, a watermark image can be formed in the next processing section x + 1 (S105: YES).

  In response to this determination, a watermark image W is formed in the next processing section x + 1 with a watermark length Lw of 0.5 m (see “processing section x + 1” in FIG. 8).

(Processing section x + 1)
Image coverage Cx in processing section x + 1: 10%
When the image coverage Cx in the processing section x + 1 is 10%, it is determined that the watermark image W is unnecessary because the image coverage Cx (10%)> the image coverage threshold Ct (5%) (S103: NO). Therefore, the watermark image W is not formed in the next processing section x + 2 (see “processing section x + 2” in FIG. 8). Note that only the image data of the print image is used for calculating the image coverage Cx in the processing section x + 1, and the image data of the watermark image W is excluded.

(Processing section x + 2)
Image coverage Cx in processing section x + 2: 1%
When the image coverage Cx of the processing section x + 2 is 1%, it is determined that the watermark image W is necessary because the image coverage Cx (1%) ≦ the image coverage threshold Ct (5%) (S103: YES). Then, the length Lw of the watermark image is determined from the image coverage Cx (S104).

  Insufficient image coverage Csh = image coverage threshold Ct−image coverage Cx = 4%.

  Therefore, the short length Lsh = Lx × Csh = 0.04 m. The watermark length Lw = Lsh / WDs = 0.04 m / 2% = 2.0 m required for the toner discharge determined from this (S102 to S104).

  Since the watermark length Lw is 2.0 m and is longer than 1 m of the watermark length threshold Lwt, it is impossible to form all the watermark images W in the area of the next processing section x + 1 (S105: NO). In response to this determination, the print job is interrupted, and a strip-shaped solid image extending in the width direction of the continuous paper S is formed as a patch b discarded during the interruption period (see “interruption period” in FIG. 8). Here, the length in the vertical direction (paper width direction) of the discarded patch b is the same as the entire image forming area of the continuous paper S, and the width of the discarded patch b (paper traveling direction) is a solid image having a density of 100%. The shortage length Lsh is 0.04 m. After the discard patch b is formed (see “interruption section” in FIG. 8), the next print job that has been immediately interrupted is resumed.

  In the present embodiment, the set watermark density setting Dws (2%) is used, and the watermark image is formed in a part of the area of the processing section with the watermark density setting Dws. However, the present invention is not limited to this. If the necessary toner discharge amount can be ensured, for example, it is assumed that it falls within the area of the processing section, and it may be formed below the watermark density setting Dws, for example, half the density and double the size. Good.

  Also, determination processing (S102 to S105) related to the formation of the watermark image W in the next processing section x + 1 is performed according to the image coverage Cx of the previous processing section x. Instead, if the determination process of the processing section x is in time before the start of the processing section x, the watermark image W of the processing section x may be formed based on the determination processing result of the processing section x. Good.

(Apply to full color mode)
The image forming method in the full color mode according to the present embodiment will be described below with reference to FIGS. FIG. 9 is a flowchart illustrating an image forming method executed by the control unit 110, and FIGS. 10 and 11 are diagrams illustrating an arrangement state of the watermark image W on the continuous paper S.

  The deterioration of the toner is determined based on the image coverage calculated from the image data of each color, and the size of the watermark image is determined according to the determination. Here, the watermark image is set to a low density that cannot be visually recognized by the user, but the visibility changes when the watermark images of a plurality of colors are overlapped. Except for a few exceptions, when a color corresponding to the toner overlay color, for example, a blue color paper, is used, the color over which the M and C toners are superimposed melts into the paper color, making it difficult to see. Thus, when a plurality of colors are superimposed, the watermark image is easily recognized by the user.

  In this embodiment, when it is determined that toner consumption by the watermark image W is necessary simultaneously for a plurality of developing devices, the watermark images are arranged side by side so as not to overlap the surface of the continuous paper S.

  FIG. 9 is a process executed subsequent to step S104 in FIG. 6. In step S121, determination is made for each color in steps S102 to S104, and it is determined whether there are a plurality of calculated watermark images W. If there is one (S121: NO), the processing from step S105 onward in FIG. 6 is performed, and if there are more than one, whether or not these watermark images can be formed is determined. Specifically, it is determined whether or not the total of the plurality of watermark lengths Lw calculated in step S104 falls within the area of the next processing section x + 1.

When it is determined that the sum of the watermark lengths Lw is equal to or less than the watermark length threshold Lwt and can be formed in the area of the next processing section x + 1 (S122: YES), a plurality of watermark images W are overlapped with the print image G2. In addition, the watermark images W are arranged in order so as not to overlap each other at a predetermined position in the processing section x + 1, for example, at the leading end reference (S123).
On the other hand, when it is determined in step S122 that the sum of the watermark lengths Lw ≦ the watermark length threshold value Lwt is not satisfied and all the watermark images W do not fit in the area of the next processing section x + 1 (S122: NO). Thereafter, the process of step S108 in FIG. 7 is executed to create a discard patch.

(Specific example of image forming method)
Hereinafter, a specific example will be described. FIG. 10 is a diagram illustrating a state in which a plurality of print images G2 are arranged on the continuous paper S in the same manner as FIG. In order to facilitate understanding, in the following, in the full color mode (Y, M, C, K) using the four developing units 152 corresponding to the four color toners, image formation of Y and K is performed. A description of the other M and C image formation will be omitted.

Here, each condition in the following specific example is shown. In the following description, the same conditions as those described in FIG. 8 are applied unless otherwise specified.
Image mode: Full color printing section distance Lc: 1 m
Image coverage threshold Ct (common to Y and K colors): 5%
K watermark density setting Dwsk: 1%
Y watermark density setting Dwsy: 5%
Watermark length threshold Lwt: 1m
(Processing section x)
K image coverage Cxk in processing section x: 4%
Y image coverage Cxy in processing section x: 10%
When the K image coverage Cxk of the processing section x is 4%, the image coverage Cxk ≦ the image coverage threshold Ct, and it is determined that the K watermark image Wk is necessary.

  K insufficient image coverage Cshk = image coverage threshold Ct−image coverage Cxk = 1%. Therefore, the short length Lshk = Lx × Cshk = 0.01 m.

  Therefore, the watermark length Lwk = Lshk / WDsk = 0.01 m / 1% = 1.0 m necessary for discharging the K toner.

  On the other hand, when the image coverage Cxy of Y in the processing section x is 10%, it is determined that the Y watermark image Wy is unnecessary since the image coverage Cxy (10%)> the image coverage threshold Ct (5%) (S103: NO) ).

  Next, it is determined whether or not the necessary watermark image W falls within the processing section x + 1. Here, there is one watermark image W (S121: NO), and since the length Lwk is 1.0 m, it is shorter than the watermark length threshold Lwt of 1 m, so that a watermark image can be formed in the next processing section x + 1. (S105: YES).

  In response to this determination, a K watermark image Wk is formed in the next processing section x + 1 with a watermark length Lwk of 1.0 m (see “processing section x + 1” in FIG. 10).

(Processing section x + 1)
K image coverage Cxk in processing section x + 1: 4.5%
Y image coverage Cxy in the processing section x + 1: 3%
When the image coverage Cxk of K in the processing section x + 1 is 4.5%, it is determined that the image coverage Cxk ≦ the image coverage threshold Ct, and the K watermark image Wk is necessary.

  K insufficient image coverage Cshk = image coverage threshold Ct−image coverage Cxk = 0.5%. Therefore, the short length Lshk = Lx × Cshk = 0.005 m.

  Therefore, the watermark length Lwk = Lshk / WDsk = 0.005 m / 1% = 0.5 m necessary for discharging the K toner.

  When the Y image coverage Cxy in the processing section x + 1 is 3%, it is determined that the image coverage Cxy ≦ the image coverage threshold Ct, and the Y watermark image Wy is also necessary.

  Y insufficient image coverage Cshy = image coverage threshold Ct−image coverage Cxy = 2%. Therefore, the short length Lshy = Lx × Cshy = 0.02 m.

  Therefore, the watermark length Lwy = Lsy / WDsy = 0.02 m / 5% = 0.4 m required for discharging Y toner.

  Next, it is determined whether the necessary watermark image W falls within the processing section x + 2. Here, there are two watermark images W (S121: YES), and the lengths Lwk and Lwy are 0.5 m and 0.4 m, respectively, so the total is 0.9 m. This is shorter than 1 m of the watermark length threshold Lwt. Therefore, a watermark image can be formed in the next processing section x + 2 (S122: YES).

  In response to this determination, a K watermark image Wk is formed with a watermark length Lwk of 0.5 m in the next processing section x + 2, and immediately after that, a Y watermark image Wy with a watermark length Lwy of 0.4 m is formed. They are formed side by side (see “Processing Section x + 2” in FIG. 10).

(Processing section x + 2)
K image coverage Cxk in processing section x + 1: 3%
Y image coverage Cxy in the processing section x + 1: 4%
When the K image coverage Cxk in the processing section x + 1 is 3%, it is determined that the image coverage Cxk ≦ the image coverage threshold Ct, and the K watermark image Wk is necessary.

  K insufficient image coverage Cshk = image coverage threshold Ct−image coverage Cxk = 2.0%. Therefore, the short length Lshk = Lx × Cshk = 0.02 m.

  Therefore, the watermark length Lwk = Lshk / WDsk = 0.02 m / 1% = 2.0 m necessary for discharging the K toner.

  When the Y image coverage Cxy of the processing section x + 1 is 4%, it is determined that the image coverage Cxy ≦ the image coverage threshold Ct, and the Y watermark image Wy is also necessary.

  Y insufficient image coverage Csy = image coverage threshold Ct−image coverage Cxy = 1%. Therefore, the short length Lshy = Lxy × Cshy = 0.01 m.

  Therefore, the watermark length Lwy = Lsy / WDsy = 0.01 m / 5% = 0.2 m required for discharging Y toner.

  Next, it is determined whether the necessary watermark image W falls within the processing section x + 2. Here, there are two watermark images W (S121: YES), and the lengths Lwk and Lwy are 2.0 m and 0.2 m, respectively, so the total is 2.2 m. Since this is longer than 1 m of the watermark length threshold Lwt, it is impossible to form a watermark image in the next processing section x + 2 (S122: NO).

  In response to this determination, the print job is interrupted, and a strip-like solid image extending in the width direction of the continuous paper S is formed as the patches bk and by during the interruption period (see “interruption period” in FIG. 10). Here, the length in the vertical direction (paper width direction) of the discard patches bk and by is the same as the entire image forming area of the continuous paper S, and the width of the discard patches bk and by (paper conveyance direction) is solid with a density of 100%. In the case of an image, the short lengths Lshk and Lshy are 0.02 m and 0.01 m, respectively. After forming the abandoned patches bk and by (see “interruption section” in FIG. 10), the next print job that has been interrupted immediately is resumed.

FIG. 11 is a diagram for explaining an arrangement state of a plurality of watermark images. FIG. 11A corresponds to the processing section x + 2 in FIG. 10, and after forming all the K watermark images Wk, the Y watermark images Wy are arranged side by side. FIG. 11B shows an arrangement in the modification. In FIG. 11B, the watermark images Wk and Wy are divided into a plurality of parts, and the divided watermark images Wk and Wy are alternately arranged. In this way, the watermark images W of the respective colors may be formed together, or may be divided and formed. This is the same when forming one watermark image W.
(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, the image forming method is executed when a second image area for forming an effective image is set in a part of the image forming area (first image area) of the continuous paper S. is there.

  FIG. 12A shows an image forming area excluding margins at both ends of the continuous paper S as a first image forming area, and FIG. 12B shows a second image forming area. 12 (c) shows the watermark image W2 formed in the “first image area excluding the second image area”, and FIG. 12 (d) shows continuous paper in FIGS. 12 (a) to 12 (c). The state superimposed on S is shown.

  Here, the “second image region” is a portion effective as a product, for example, a region where a label image is formed. This label image is an image that is used after being separated from the mount in the subsequent post-processing. The label image is an area used as a product. On the other hand, the “first image area excluding the second image area” other than the label is not used as a product, and is discarded after the label is used. It is an area.

  In the second embodiment, the watermark image W2 is formed only in the “first image area excluding the second image area”. In this way, it is not necessary to set the density of the watermark image to an excessively low density in consideration of safety, and the watermark density setting can be set to a relatively high value. As a result, a large amount of toner can be discharged (consumed) from the developing device 152 as a watermark image W at an early stage. Even if the watermark density setting is increased and the watermark image W2 can be visually recognized by the user, it is valuable as a product. Since no watermark image is formed in this image area, the quality of the product is maintained.

  Note that when the continuous paper type is label paper, the control unit 110 determines the input image data region to be printed as the second image region. Instead of this, the user may set the range of the second image area when using continuous paper or cut paper.

(Third embodiment)
The third embodiment will be described with reference to FIGS. 13 and 14. In the third embodiment, a uniform watermark image W3 is formed with the density set by the watermark density over the entire surface of one print job, that is, the entire image formation area of the continuous paper S corresponding to the print job.

  FIG. 13 is a flowchart illustrating an image forming method executed by the control unit 110, and FIG. 14 is a diagram illustrating a state in which a watermark image W3 is formed on the entire surface of the continuous sheet S.

  When a print job is started in response to a user instruction, the control unit 110 determines whether or not to form the watermark image W3 in the entire image forming area corresponding to the print job based on whether or not the degree of deterioration is a predetermined value or less. (S401). Specifically, the determination is made based on whether or not the condition of watermark density setting DWs ≧ image coverage threshold Ct is satisfied.

  The watermark density setting DWs can be set by the user, and if it is set to 5% density, the condition of step S401 is satisfied (S401: YES), so the density (5) of the watermark density setting DWs for the print job. %), A watermark image W3 is formed (S402), and this is executed on the entire surface of the print job until the print job is completed (S403).

  When the watermark image W3 is formed on the entire surface of the image forming area of the paper (cut sheet, continuous paper) corresponding to the print job, the boundary of the watermark image W3 does not exist inside the image forming area. It becomes more difficult to visually recognize the image W3. The third embodiment is preferably applied in mono color, but the image forming area is divided into a plurality of band-like areas extending along the conveyance direction of the continuous paper S, and each color is divided into each band area. An area for arranging the watermark image may be assigned.

(Modification of the third embodiment)
As a modification, a uniform watermark image W3 may be formed on the entire surface of continuous paper (or cut paper) corresponding to a print job by performing the following processing.

  Specifically, in the example of FIG. 8 and the like, the section distance Lc is set to 1 m, but this is set to the same length as the entire length of the print job. Then, before starting the print job, the entire image coverage is calculated based on all image data of one print job. Then, it is determined whether or not a watermark image can be formed by the processing in steps S103 to S105 in FIG. 6, and if it is determined that a watermark image can be formed, the necessary amount of toner is discharged at a uniform density on the entire surface of the print job. The process is executed using the formed watermark image W3. Specifically, a watermark image W3 having a length Lc (full length) is formed at the density (%) of the insufficient image coverage Csh. In such a modification, the same effect as that of the third embodiment can be obtained.

(Other variations)
In the first and second embodiments, an example of 1 m is shown as the section distance Lc of the processing section. However, distances longer than this may be set, for example, 10 m and 100 m. Further, the processing section having the length of the continuous paper S in the conveyance direction as a unit has been described as a unit of processing. When an image is formed on a cut sheet, a predetermined number of sheets may be used as a processing unit.

  In the present embodiment, the degree of toner deterioration is determined based on the toner consumption amount, and the image coverage in the processing section is used as an index of the toner consumption amount. However, instead of the image coverage, the toner supply from the toner supply unit 190 is performed. An amount may be used. The toner replenishment amount can be obtained from the driving time of the toner conveying member of the toner replenishing unit 190.

  In addition, the present invention is construed as being limited only by the scope of the claims, and is not construed as being limited to the above-described apparatus configuration example, assumed example, or the like of the present embodiment.

DESCRIPTION OF SYMBOLS 10 Image forming system 100 Image forming apparatus 110 Control part 111 Image control CPU
112 DRAM control IC
113 Nonvolatile memory 114 Image memory 115 RTC
116 Compression / decompression IC
117 Read processing unit 118 Write processing unit 120 Print controller unit 121 Controller control unit 122 DRAM control IC
123 Image memory 124 Communication I / F
130 Operation Display Unit 140 Scanner 150 Image Forming Unit 151 Photosensitive Drum 152 Developer 153 Intermediate Transfer Belt 154 Fixing Unit 160 External Device Control Unit 190 Toner Replenishment Unit 200 Paper Feed Device 300 Paper Feed Adjustment Device 400 Paper Discharge Adjustment Device 500 Winding Device 160 External device control unit W, Wk, Wy, W2, W3 Watermark image Cx, Cxk, Cxy Image coverage Csh, Cshk, Csy Insufficient image coverage Dws, Dwsk, Dwsy Watermark density setting Lc Section distance Lwt Watermark length threshold Lw, Lwk, Lwy Watermark length Lsh, Lshk, Lshy Insufficient length Wdx Discard patch band width S Continuous paper

Claims (9)

An image forming unit for developing an electrostatic latent image formed on a photoconductor based on a print job with toner, and forming the image on the paper by transferring the developed toner to the paper;
A toner replenishing section for replenishing toner to the developing device;
The degree of deterioration of the toner in the developing device is determined based on the amount of toner consumed, and the image forming unit is controlled according to the degree of deterioration to display a watermark image for discharging the toner in the developing device on a sheet. A control unit that forms an image based on the print job in an image forming area;
An image forming system. The watermark image has a uniform density over the entire surface, and the control unit determines a discharge amount of toner according to the degree of deterioration, and determines a size of the watermark image according to the discharge amount.
The image forming system according to claim 1. There are a plurality of the developing units, and each developing unit stores different color toners,
The image forming system according to claim 1, wherein the control unit sets a density of the watermark image for each toner color. It has an input unit that accepts user settings,
The image forming system according to claim 1, wherein the control unit changes the density of the watermark image based on a density setting received by the input unit. The control unit executes the determination of the degree of deterioration of the toner and the determination of the discharge amount every time the image formation length reaches a predetermined length as a processing section or each time the developing unit reaches a predetermined operation amount. ,
If the amount of toner discharged when the watermark image is formed in the entire next processing section does not reach the determined amount of discharge, the control unit forms a solid image band to form a toner image. Perform the discharge,
The image forming system according to any one of claims 1 to 4. When the second image area for forming an effective image is set in a part of the area of the first image area, which is an area where image formation is possible on the paper,
The image forming system according to claim 1, wherein the control unit forms the watermark image in the first image area excluding the second image area. When executing the print job, the control unit uniformly forms a watermark image with the density on the entire image forming area of the paper corresponding to the print job based on the set density of the watermark image. Determining the deterioration degree of the toner in the developing device in the case,
2. When forming an image based on the print job, the control unit forms the uniform watermark image at the density on the entire surface of an image forming area of a sheet when the degree of deterioration is determined to be a predetermined value or less. 5. The image forming system according to 4. The control unit determines the degree of deterioration of the toner in the developing device based on image data of the print job when executing the print job,
7. The image forming apparatus according to claim 1, wherein when forming an image based on the print job, the control unit forms the uniform watermark image on the entire surface of the image forming area of the paper according to the determination. The image forming system described in 1. A developing unit that develops the electrostatic latent image formed on the photosensitive member based on a print job with toner; and an image forming unit that forms an image on the sheet by transferring the developed toner to the sheet; and the developing unit An image forming method in an image forming system comprising: a toner replenishing unit that replenishes toner;
Determining the degree of deterioration of the toner in the developing device according to the amount of toner consumed;
By controlling the image forming unit according to the degree of deterioration, a watermark image for discharging the toner in the developing device is formed in an image forming area for forming an image based on the print job on a sheet. Steps,
An image forming method comprising: