JP4661546B2 - Printing device - Google Patents

Description

  The present invention relates to a printing apparatus that includes a plurality of print engines and that prints one print job by distributing the print jobs to the plurality of print engines.

  As printing apparatuses incorporating a plurality of print engines, there are those shown in Patent Document 1 and Patent Document 2. Further, Patent Document 3 discloses a configuration in which print engines are arranged in a tandem configuration in order to obtain high speed and various paper conveyance properties.

  As described above, in a printing apparatus provided with a plurality of print engines, one print job is often distributed to the plurality of print engines for printing. In such a case, the printed results of the sorted pages may be collected and discharged on one discharge tray.

  In such a printing apparatus, if the image quality characteristics such as the darkness (in the case of monochrome printing) and the hue (in the case of a color printer) of the printing result differ for each print engine, the printing quality of one printing apparatus is poor. I must say. However, in electrophotographic print engines, characteristics such as toner chargeability change depending on the amount of toner in the developing unit or toner cartridge, which leads to a change in print quality. If the pages are simply sorted, there is a possibility that the print quality may differ between print engines.

  Japanese Patent Application Laid-Open No. 2004-228561 discloses a mechanism for automatically selecting a printer having an ink amount necessary for printing a job or a page and performing printing in a printing system in which a plurality of printers are connected. This mechanism is effective in ensuring that the job or page can be printed reliably, but it is not effective in making the print quality uniform between printers.

U.S. Pat. No. 4,427,285 JP-A-2-215623 JP-A-9-127739 JP 2002-096485 A

  According to the present invention, the amount of toner (or ink) of a plurality of print engines provided in a printing apparatus is made as uniform as possible, and the difference in print image quality of each engine is reduced.

  The present invention is a printing apparatus that includes a plurality of print engines connected to a common paper transport unit that extends from a paper feed unit to a paper discharge unit, and distributes an input print job to each print engine for printing. For each predetermined printing unit comprising consumption calculation means for calculating the predicted consumption of marking material used to print each sheet based on the print data of each sheet to be printed, and a group of sheets to be printed continuously In addition, based on the predicted consumption of the marking material for each sheet calculated by the consumption calculation means, the print output unit so that the total of the predicted consumption of the marking material for each print engine in the print unit is uniformized Distribution control means for distributing and printing the respective sheets to the respective print engines.

  Here, “sheet” refers to one sheet of paper, one sheet for one-sided printing and one sheet for two front and back pages for double-sided printing. “Marking material” refers to toner or ink used for printing (marking). The “consumption calculation means” prints the number of pixels of an image to be printed on one sheet (in the case of a binary image) and the number of pixels in consideration of the print density (in the case of a multi-valued image) such as a pixel counter. It is a means to obtain from data. The “predetermined printing unit composed of continuously printed sheet groups” may be, for example, a print job, or a continuous sheet group of a predetermined number of sheets.

  In a preferred aspect of the present invention, the distribution control means divides the printing unit into sets of N sheets, where N is the number of print engines provided in the printing apparatus, and each sheet belonging to the set is assigned to each set. Under the condition that each print engine is distributed one by one, the sheet distribution is determined so that the total estimated consumption of the marking material for each print engine in the printing unit becomes uniform.

In the reference example , the printing apparatus includes a plurality of print engines connected to a common paper transport unit extending from the paper feed unit to the paper discharge unit, and distributes an input print job to each print engine for printing. Consumption amount for calculating the estimated consumption amount of the marking material used for printing each sheet based on the remaining amount monitoring means for monitoring the remaining amount of the marking material of each print engine and the print data of each sheet to be printed A remaining amount of marking material of each print engine indicated by the remaining amount monitoring unit at a printing start time of the printing unit for each predetermined printing unit composed of one or more sheets that are continuously printed; Based on the estimated consumption of marking material for each sheet calculated by the consumption calculation means, the marking material of each print engine at the end of printing of the printing unit As the remaining amount becomes uniform, to provide a distribution control means for printing sorting them each sheet to each of the print engine, the printing apparatus comprising a.

Here, the remaining amount monitoring means may be a sensor that measures the remaining amount of the marking material, or may obtain the remaining amount by sequentially subtracting the pixel count value of each sheet from the capacity of the marking material container. . It is also clear that the remaining amount of marking material and the total consumption amount are equal to the capacity of the marking material container when added together, so it is possible to monitor the total consumption amount instead of monitoring the remaining amount. also by the same process is Ru can be realized.

  The best mode for carrying out the present invention (hereinafter referred to as “embodiment”) will be described below with reference to the drawings.

  FIG. 1 is a diagram illustrating a schematic configuration of an example of a printing apparatus to which the present invention is applied.

  The printing apparatus includes one paper feeding unit 100, two printing units 200 and 300, and one paper discharge unit 400.

  The paper feed unit 100 includes a plurality of paper feed trays (three are illustrated in the figure) 101, 102, and 103. The paper fed from each of the paper feed trays 101 to 103 is supplied to the printing unit 200 connected to the subsequent stage of the paper feed unit 100 through the paper feed conveyance path 105.

  The two printing units 200 and 300 include electrophotographic print engines 201 and 301 for full-color printing, respectively.

  In this example, the print engines 201 and 301 have a configuration in which four color developing units 203 and 303 of Y (yellow), M (magenta), C (cyan), and K (black) are arranged in tandem (columns). Yes. Each of these four-color developing sections 203 and 303 forms a toner image of each color by electrophotography, and these four-color toner images are transferred onto the intermediate transfer belts 205 and 305, respectively. A full-color toner image is formed. The full-color toner images on the intermediate transfer belts 205 and 305 are transferred to the paper by the transfer units 207 and 307. The sheet on which the toner image is transferred is sent to the fixing units 209 and 309, where the toner image is fixed on the sheet. In the case of performing double-sided printing, after fixing the front surface, the fixed paper is once sent to the switchback paths 214 and 314, and then conveyed in the reverse direction to carry the reverse conveying paths 216 and 316. The paper is reversed by introducing the paper to the transfer unit 207, 307 and the back side is printed.

  The two printing units 200 and 300 are connected in tandem. That is, the printing unit 200 receives paper from the paper supply unit 100, and the printing unit 300 receives paper discharged from the printing unit 200. Then, the paper discharged from the printing unit 300 is introduced into the paper discharge unit 400 and discharged to the paper discharge stacker 401 through the paper discharge transport path 405. Hereinafter, for identification, the upstream printing unit 200 in the tandem arrangement as viewed from the paper feeding unit side is referred to as A unit, and the downstream printing unit 300 is referred to as B unit.

  The configuration of both the A and B units (200 and 300) will be described in detail as follows.

  That is, the A unit accepts a sheet supplied from the sheet feeding conveyance path 105 of the sheet feeding unit 100, and when printing on the sheet by the A unit, the sheet 210 conveys the sheet conveyance path by the print engine 201. To the transport path 212 toward As a result, the sheet is introduced into the print engine 201, the toner image is transferred by the transfer unit 207, and the toner image is fixed by the fixing unit 209. When performing double-sided printing on the paper, the paper for double-sided printing is transported as described above, and the back side is printed. In this way, the paper on which printing has been completed is sent to the B unit through the paper discharge transport path 217. The above is the case where the A unit performs printing on the paper supplied from the paper feeding unit 100. However, when printing is not performed on the paper using the A unit, the paper passes by switching the gate 210. Is sent to the transport path 215, and further to the B unit through the transport path 217 for paper discharge.

  Although the operation of the A unit has been described above, the operation of the B unit is the same. That is, when printing is performed on the paper supplied from the A unit by the B unit, the paper is sent to the transport path 312 toward the print engine 301 by switching the gate 310, and after the image is printed, the paper discharge unit. It is discharged to 400. Further, when printing is not performed in the B unit, the sheet is similarly discharged by the switching of the gate 310 to the paper discharge unit 400 through the transport path 315 for passage.

  Depending on the configuration of the printing apparatus, a post-processing unit that performs post-processing such as stapling and punching may be provided. In such a case, the post-processing unit can be provided at the rear stage of the paper discharge unit 400. .

  The A unit control unit 220 and the B unit control unit 320 are responsible for the control of paper conveyance and printing in both the A and B units as described above. The control units 220 and 320 and the control units (not shown) of the paper supply unit 100 and the paper discharge unit 400 are respectively configured according to instructions from a printer controller 500 (see FIG. 2 and the like) that controls the entire printing apparatus. By controlling each part in the unit, integrated operation control is realized as the entire printing apparatus.

  The printing apparatus described above can be regarded as a configuration in which the print engines 201 and 301 are connected to a series of paper conveyance paths including the conveyance paths 105, 215, 315, and 405, that is, the conveyance paths 105 and 215. , 315, and 405 are a common sheet conveyance path for the two print engines 201 and 301.

  The printing apparatus of FIG. 1 has two printing units 200 (A unit) and 300 (B unit), so that a high-speed printing operation is possible.

  That is, in this printing apparatus, printing is performed by alternately supplying sheets supplied from the sheet feeding unit 100 to the A unit and the B unit for each sheet. That is, the individual sheets are printed only in one of the units A and B, and the other unit passes through the passing conveyance path 215 or 315 (that is, passes through that unit without printing). In the sheet conveyance paths 105 and 405 common to both units (all sheets pass through this path), the sheet conveyance paths 212, 214, 216, 312, 314, and 316 in the individual print engines 201 and 301 are doubled. Convey paper at a speed of. As a result, the entire printing apparatus can perform printing at twice the printing speed of the individual print engines 201 and 301. Similarly, the paper may be transported at the double speed (or higher speed) in the passing transport paths 215 and 315.

  In the following, the control for equalizing the toner consumption of both the A and B units in such a printing apparatus will be described.

  FIG. 2 shows a functional configuration of the printing apparatus. In FIG. 2, the same reference numerals are given to the components corresponding to the components shown in FIG. In FIG. 2, the paper supply unit 100 and the paper discharge unit 400 are not shown.

  In FIG. 2, a printer controller 500 is a control unit that controls a printing unit 200 (A unit) or 300 (B unit) to perform a printing operation. The printer controller 500 receives PDL (page description language) data 1000 of a print job via a network or the like, creates raster image data of each page from the PDL data 1000, and stores the raster image data of the page as A units 200 and B. The units 300 are distributed and supplied, and printing is performed respectively.

  Among the functional modules in the print controller 500, the PDL interpretation unit 502 interprets the PDL data 1000 and converts it into data in a predetermined intermediate code format (the intermediate code format may be well known). Here, the color of the image indicated by the intermediate code data is a value in the color space of the computer on the PDL data creation side, for example, RGB format, but the color space conversion unit 504 is the color space of the printing units 200 and 300. Convert to CMYK format. The rasterization unit 506 generates raster image data from the intermediate code data after color space conversion. The above-described PDL interpretation unit 502, color space conversion unit 504, and rasterization unit 506 exist conventionally, and such a conventional one can be used.

  The pixel counter 510 is a means for counting the number of pixels (that is, pixels) of each page to be printed indicated by the PDL data 100. For example, the pixel counter 510 counts the number of on pixels (that is, pixels on which printing is performed) in the raster image generated by the rasterization unit 506. In the case of a full-color printing apparatus, the number of ON pixels is counted for each color of C, M, Y, and K. If the raster image generated by the rasterization unit 506 is a binary image, the count value, that is, the pixel count, can be regarded as a value indicating the amount of toner consumption. Further, when the pixel count is obtained from the image data, the image data has not yet been printed, so the pixel count can be regarded as a predicted value of toner consumption.

  When the raster image generated by the rasterization unit 506 is not a binary image but a multi-value image (in the case of a full-color image, a multi-value image for each color of C, M, Y, and K), the pixel counter 510 The value corresponding to the toner consumption amount is obtained by counting the value according to the gradation value (that is, the print density) of the on pixel, not the number of on pixels itself.

  Note that the pixel count can be estimated at the stage of PDL interpretation by the PDL interpretation unit 502 as well as counting raster images. Such a pixel counter is conventionally used for estimating the toner consumption for print density control, toner replenishment control, and the like. The pixel counter 510 in the present embodiment is also such a conventional one. Can be used.

  In the present embodiment, the pixel counter 510 calculates a pixel count for each page of print image data indicated by the PDL data 1000 and supplies this to the distribution unit 508 and the cumulative value holding unit 512.

  The accumulated value holding unit 512 accumulates the pixel count for each page supplied from the pixel counter 510 and holds the accumulated value. The accumulated value held in the accumulated value holding unit 512 is updated every time the pixel count of each page is supplied from the pixel counter 510. In a full-color printing apparatus, a cumulative pixel count is held for each color of C, M, Y, and K. The accumulated value held by the accumulated value holding unit 512 is reset, for example, when the toner cartridge is replaced.

  The distribution unit 508 performs control for distributing the raster image data generated by the rasterization unit 506 to the A unit 200 and the B unit 300 for each page. In one preferable aspect, the distribution unit 508 controls distribution based on the pixel count for each page supplied from the pixel counter 510 so that the toner consumption of the A unit 200 and the B unit 300 is made uniform. In another preferred embodiment, the distribution unit 508 further uses the cumulative value information held by the cumulative value holding unit 512 to perform distribution so that toner consumption between both units is uniform. Details of this sort control will be described later.

  In the A unit 200 and the B unit 300 that have received the raster image data of the page from the distribution unit 508, the halftone processing units 222 and 322 digitally process the raster image data of the C, M, Y, and K color plates of the page. By applying the halftone screen for the color plate by halftone processing, binary page image data is generated.

The print engines 201 and 301 control the ROS (raster output scanner) based on the binary page image data supplied from the halftone processing units 222 and 322 to expose the photosensitive drum, and the exposed latent image is displayed. Printing is executed by developing with toner and transferring it to paper.

  As is well known, the result of dividing the pixel count by the total number of pixels on the page instead of the pixel count itself (in the case of a multi-valued image, divided by the pixel count when all the pixels have the highest density). The area coverage (also called the printing rate), which is the result, may be used for the estimation of toner consumption. If the page size is uniform, the pixel count per page and the area coverage have the same meaning. Therefore, even if the area coverage is obtained by the pixel counter 510 and the distribution unit 508 controls the distribution based on the area coverage instead of the pixel count, there is no problem in the case of printing a print job including only pages of the same size. .

  Next, details of distribution control by the distribution unit 508 will be described. As shown in FIG. 3, the distribution control of the present embodiment has two types of distribution modes: “normal distribution” (S16) and “toner consumption leveling (uniformization) distribution” (S18). The normal distribution is a mode in which image data of pages of a print job is distributed in order to each print engine according to the page order. In an apparatus having two printing units 200 and 300 as shown in FIGS. 1 and 2, pages of a print job are alternately allocated to both units in this mode. On the other hand, in the toner consumption leveling distribution, the distribution destination of each page is adjusted so that the toner consumption of each print engine is approximately the same.

  Note that the sorting in units of “pages” in the previous stage is an example of single-sided printing. In the case of double-sided printing, the unit assigned to each print engine is not a single page of image data, but a pair of image data on the front and back sides of one sheet of paper. Therefore, when generalizing in consideration of both single-sided and double-sided printing, the sorting unit is image data to be printed on one sheet of paper (one page for single-sided, two pages for front and back for double-sided). The term “sheet” in the sense of “one sheet of paper” will be referred to as “sheet” and will be described below using the concept of “sheet”. In this case, the pixel count (or area coverage) is also calculated for each sheet.

  In the basic control operation shown in FIG. 3, the distribution unit 508 first determines whether or not the print job (PDL data 1000) is a job for a plurality of sheets (S10). The “multiple sheet object” is a job in which a document (PDL data 1000) includes a plurality of pages (single side) or a plurality of sheets (double side). Conversely, there may be a case where a large number of originals including only one page or one pair of front and back sides are printed. In this case, the determination result in S10 is negative (N). Whether or not the print job is a multi-page object can be determined by analyzing the PDL data 1000.

  If the determination result in S10 is negative (N), this is a case where a document including only one page or one pair of front and back sides is printed. Even if multiple copies are printed, there is a gap between printed sheets. There is no difference in pixel count (and area coverage and toner consumption). If there is no difference in pixel count between sheets in this way, there is no difference in toner consumption between print engines simply by distributing each sheet to each print engine (printing unit) according to the sheet order. Mode distribution is executed (S16).

  If the determination result in S10 is affirmative (Y), the distribution unit 508 acquires the pixel count of all sheets in the print job (ie, the original) from the pixel counter 510 (S12), and calculates the difference in pixel count between the sheets. The brute force is examined, and it is determined whether or not the difference between the sheets exceeds a predetermined allowable value (S14). If all the differences in the combination of sheets in the job are less than the allowable value, it is considered that there is almost no difference in toner consumption between the print engines no matter how they are distributed. Sort by mode. The “allowable value” that is the criterion for the determination in S14 is obtained in advance by experiments or the like and registered in the printer controller 500.

  If it is determined in S14 that the difference between any of the sheets exceeds the allowable value, the process proceeds to toner consumption leveling distribution mode processing (S18).

  Note that the basic concept of the processing procedure of FIG. 3 is that normal distribution (S16) is adopted if the variation in pixel count between sheets in the print job is small, and toner consumption leveling distribution (S18) is adopted if large. Therefore, the process of S14 that compares the difference between the sheets with the allowable value is merely an example of one method for determining the magnitude of variation. Therefore, another determination process may be used instead of the determination process of S14.

  Next, details of the toner consumption leveling distribution (S18) will be described with reference to FIG.

  In this process, first, each sheet of the print job is temporarily allocated according to the distribution method in the normal distribution mode (S20). This temporary distribution is for calculation processing, and at this stage, the image data of each sheet is not actually distributed to the print engine.

  In this embodiment, on the basis of the provisional distribution state, a simulation is performed by changing the distribution (that is, the correspondence between the sheet and the print engine that prints it), and for each case where the distribution is changed. In this case, the pixel counts of sheets printed by each print engine are summed for each print engine (S22). Then, a case where the difference (variation) between the total values of each print engine is minimized is adopted, and each sheet is distributed to each print engine according to the distribution pattern indicated by the case (S24). In the case where the difference between the total values is the smallest, find all possible distribution destination change cases as brute force, and find the difference in the total area coverage between the engines for each case. You can choose the one that gives the minimum value.

  According to the distribution process as described above, the difference in toner consumption between the print engines at the time when the print job is completed can be minimized.

  Further, in the distribution change simulation of S22, if the change of distribution is limited to a set of N sheets (N is the number of print engines included in the printing apparatus) from the beginning of the job, a plurality of prints can be obtained. The distribution can be optimized from the viewpoint of uniform toner consumption without losing the advantage of high speed by parallel printing in the engine (printing unit).

  That is, for example, in the case of a printing apparatus having two print engines as shown in FIGS. 1 and 2, printing is performed by the effect of parallel processing in which one of two continuous sheets is printed by the A unit 200 and the other is printed by the B unit 300. The printing speed is almost double that of a single engine. Therefore, if the distribution destination is changed between each pair of two sheets from the beginning of the job, the printing speed does not decrease from about twice that of a single engine. Therefore, if a distribution destination change simulation is performed under this constraint condition, It is possible to achieve both uniform toner consumption and high printing speed.

  For example, consider a case where an 8-sheet print job is processed by a printing apparatus having two print engines. In this case, it is assumed that the result of the temporary distribution in the normal distribution mode is as shown in FIG. In the table shown in the figure, “# 1” and “# 2” are print engine identification numbers. For example, print engine # 1 corresponds to A unit 200 and # 2 corresponds to B unit 300. Each row of the table indicates two pairs from the beginning of the job. In the case of temporary allocation, odd-numbered sheets are allocated to engine # 1, and even-numbered sheets are allocated to engine # 2. Numerical values such as “30” and “70” shown in each cell of the table are area coverage values (percentage values) of the corresponding sheets. In the example of (a), the total area coverage of the entire print job is greatly different from 100 for engine # 1 and 300 for engine # 2. If the change simulation is performed under the condition that the distribution change is allowed only in the pair of 2 sheets, as shown in (b), if the distribution destination of the 5th-6th pair is replaced, both engines In both cases, the total area coverage is 200, and it can be seen that the toner consumption in the job is made uniform. Of course, this is not limited to the case of complete equalization, but according to the processing of FIG. 4, the difference in toner consumption when processing the job of each print engine can be made as small as possible.

  In the above example, a distribution pattern that minimizes the difference between the total pixel counts between the print engines is obtained in S24. However, if the number of sheets of the job increases, the calculation amount increases and the processing takes time. Is concerned. Therefore, in S24, it is determined whether or not the difference between the total pixel counts between the print engines is within a predetermined allowable value (this is registered in the printer controller 500 in advance). It is also preferable to discontinue the change simulation (S22) and adopt the case of the difference within the allowable value as the actual distribution pattern.

  In the above, a printing apparatus having two print engines has been exemplified. However, it is obvious that the same toner consumption leveling distribution can be performed by a printing apparatus having three or more print engines. The only difference from the two units is that the number of distribution destinations increases. In general, in the case of an apparatus with N print engines (N is an integer of 2 or more), jobs are divided into groups of N sheets from the top, and sorting is performed under the condition that only the group can be changed. By making the previous change, the toner consumption between the print engines can be made uniform.

  In FIG. 5, for the sake of simplicity, a monochrome print engine using a single toner is taken as an example. However, a color print engine using a plurality of color toners such as C, M, Y, K, etc. Even in this case, the above method is applicable. In the case of color, the change from monochrome is that it is necessary to determine the replacement so as to uniformize the overall difference in consumption of toner of a plurality of colors. For this purpose, for example, a distribution pattern in which the sum of squares or the mean square of the difference between the engines of the total pixel count for each color of C, M, Y, and K is minimum (or less than a predetermined allowable value) is obtained. That's fine.

  FIG. 6 shows an example of sorting in the case of color. In this example, at the time of temporary allocation, as shown in (a), the difference in area coverage between engines was 60, 20, 20, and 60 for Y, M, C, and K, respectively. Thus, as shown in (b), the toner consumption of each color in the job can be made uniform by changing the distribution destination of the pair of the third and fourth sheets.

  In the above example, control is performed so that the toner consumption of each engine is made uniform for each print job. However, since it is not possible to distribute until the pixel count of all pages of the job is obtained, the number of pages is reduced. Many jobs take time to start printing. One method for improving this is a method in which the toner consumption leveling process is performed in units defined by the number of sheets such as 10 sheets or 100 sheets instead of jobs. In this method, the unit of processing in steps S22 and S24 in the procedure of FIG. 4 is changed to a predetermined number instead of a job, and the processing content itself does not need to be changed.

  In the above embodiments, the difference in toner consumption between print engines can be reduced in units of jobs and sheets, but it is difficult to completely reduce the difference to zero. For this reason, as the unit of the number of jobs and sheets is executed several times or several tens of times, there is a possibility that a small difference will become a large difference intentionally. In addition, since the number of print sheets in a job is not necessarily an integral multiple of the number of print engines, the remainder that cannot be divided by the number of engines can be divided into engines that cannot be distributed and the difference in toner consumption. Will come out. As a technique for reducing such a cumulative difference, there is a processing procedure as shown in FIG. In FIG. 7, the same steps as those in the procedure of FIG.

  In the processing procedure of FIG. 7, information on the cumulative value held in the cumulative value holding unit 512 is used. In other words, the distribution unit 508 acquires the cumulative value of the pixel count at that time of each print engine from the cumulative value holding unit 512 at the start of the job (S21). The accumulated value acquired at this time is a value immediately before the start of the print job, and the pixel count of the sheet of the job is not added. In S22a, for each case (that is, the distribution change pattern) obtained by the distribution change simulation, the total pixel count of each print engine in the case (this is a predicted value of toner consumption in the job). The pixel count cumulative estimated value at the end time of each print engine job is obtained by adding to the pixel count cumulative value immediately before the start of the job of the print engine (obtained in S21, which is the cumulative total of past toner consumption). Ask. Then, the case where the difference in the pixel count cumulative prediction value of each engine is minimized is adopted as the actual distribution pattern (S24a).

  In this way, by performing leveling in consideration of information on the total amount of toner consumption up to the start of the job, the toner consumption of each print engine can be made more uniform.

  Note that the procedure of FIG. 7 can also be executed in other units such as the number of sheets instead of the job.

  Further, as another method for reducing the cumulative difference in toner consumption, a process as shown in FIG. 8 is also suitable.

  In the process of FIG. 8, a mode called a leveling priority mode is provided in the printing apparatus so that the user can select this mode. The leveling priority mode is a mode that prioritizes leveling of toner consumption over printing speed. When this mode is selected by the user (the determination result in S30 is Y), the distribution unit 508 acquires the pixel count cumulative value of each print engine at the job start time from the cumulative value holding unit 512 (S32), When the difference between the accumulated values of the engines is obtained and the difference exceeds a predetermined allowable value (also registered in the printer controller 500 in advance) (the determination result in S34 is Y), the accumulated value is small. The sheet is distributed to the other print engine (S36). The distribution to the print engine in S36 may be one sheet at a time, a plurality of sheets (the number of sheets is determined in advance), or a job unit. Then, when the distribution in S36 is completed, the process returns to S32 again to acquire the pixel count cumulative value of each engine at that time, and the same processing is repeated.

  When the leveling priority mode is not selected, or when the difference between the cumulative values between the engines is less than or equal to the allowable value (or when it becomes less than the allowable value in the distribution in S36), the basic control operation shown in FIG. (S38).

  When there is a large difference in the pixel count cumulative value between engines, the sheet is preferentially allocated to the engine with a small cumulative value in this way, but the printing speed is slowed down, but the difference in toner consumption between the engines is quick. Can be resolved.

  The example of FIG. 8 is an example when there are two print engines. However, when there are three or more print engines, for example, the difference in cumulative values with the engine with the largest pixel count cumulative value is greater than or equal to the allowable value. The sheets may be distributed among the print engines.

  Some printing apparatuses include a toner remaining amount sensor that measures the remaining amount of toner in the toner cartridge. The remaining amount obtained from the remaining toner amount sensor has a certain relationship with the cumulative pixel count value. It is in. That is, in principle, when the toner amount corresponding to the cumulative pixel count is subtracted from the capacity of the toner cartridge, it becomes equal to the remaining amount. Therefore, as shown in FIG. 9, if the remaining amount information output from the toner remaining amount sensors 224 and 324 provided in the respective printing units 200 and 300 is given to the distributing unit 508, the distributing unit 508 outputs this information to the pixels. The same processing as shown in FIGS. 7 and 8 can be executed by using instead of the accumulated count value. That is, in the above-described example, the control is performed so that the toner consumption amount is made uniform between the engines, but this is substantially equivalent to making the remaining amount of toner uniform.

  There are also sensors that measure the amount of toner consumed in the toner cartridge instead of the remaining amount of toner, but it will be apparent that such a consumption sensor can also be used in the same manner as the above-mentioned remaining amount sensor.

  In addition, the printing apparatus includes means for obtaining the total amount of toner consumption (total pixel count) and the remaining amount of toner as needed (that is, a pair of the pixel counter 510 and the cumulative value holding unit 512 or the remaining toner amount sensors 224 and 324). In this case, leveling processing as shown in FIG. 10 is also possible.

  In the process of FIG. 10, the toner consumption between the engines is leveled not in units of print jobs but in units of N (the number of print engines in the printing apparatus) from the top of the print job. That is, when trying to sort N consecutive sheets, the remaining toner amount of each engine at that time is acquired from the remaining toner sensor (S40). Or in S40, you may acquire the pixel count cumulative value of each engine at that time (however, when N pixel counts to be distributed are not reflected). Then, the pixel count of each of the N sheets to be distributed is acquired from the pixel counter 510 (S42). Then, the distribution is determined so that the sheet with the larger pixel count is assigned to the print engine with the larger amount of remaining toner (that is, the smaller pixel count cumulative value) (S44). The processes of S40 to S44 are repeated until the end of the print job (S46). By such processing, the difference between the engines in the total toner consumption (and the toner remaining amount) can be reduced for every N sheets printed in parallel by N print engines.

  According to the apparatus of the embodiment and the modification described above, the toner consumption of each print engine can be made uniform, so that the characteristics such as the chargeability of the toner of each print engine can be made uniform. Can be suppressed. Further, since the toner consumption of each print engine can be made uniform, the replacement timing of consumables such as a toner cartridge and a photosensitive drum can be made uniform among the print engines.

  Note that the distribution unit 508 in the above embodiments and modifications can be typically realized by causing a processor to execute a control program describing the processing of the distribution unit 508 described above.

It is a figure which shows an example of the printing apparatus with which this invention is applied. FIG. 3 is a diagram illustrating an example of a functional configuration of a printing apparatus according to the present invention. It is a flowchart which shows the procedure of the basic control operation | movement of a distribution part. 6 is a flowchart illustrating a procedure for distributing toner consumption leveling. FIG. 10 is a diagram illustrating a specific example (in the case of monochrome printing) of toner consumption leveling distribution. FIG. 10 is a diagram illustrating a specific example (in the case of full color printing) of toner consumption leveling distribution. It is a flowchart which shows the process sequence of a modification. It is a flowchart which shows the process sequence of another modification. FIG. 9 is a diagram illustrating a functional configuration of a modified example using a toner remaining amount sensor. It is a flowchart which shows the process sequence of another modification.

Explanation of symbols

  100 paper feeding unit, 200, 300 printing unit, 201, 301 print engine, 400 paper discharge unit, 500 print controller, 502 PDL interpretation unit, 504 color space conversion unit, 506 rasterization unit, 508 sorting unit, 510 pixel counter, 512 Cumulative value holding unit.

Claims (7)

A printing apparatus that includes a plurality of print engines connected to a common paper transport unit that extends from a paper feed unit to a paper discharge unit, and that sorts and prints input print jobs to the print engines.
Consumption calculation means for calculating the predicted consumption of the marking material used to print each sheet based on the print data of each sheet to be printed;
Based on the predicted consumption of marking material for each sheet calculated by the consumption amount calculation unit for each predetermined printing unit consisting of a group of continuously printed sheets, the marking material for each print engine in that printing unit A distribution control unit that distributes and prints the sheets in the print output unit to the print engines so that the total predicted consumption is uniform;
A printing apparatus comprising:   The distribution control unit divides the printing unit into groups of N sheets, where N is the number of print engines included in the printing apparatus, and distributes each sheet belonging to the group to each print engine. 2. The printing apparatus according to claim 1, wherein the sheet distribution is determined so that the total estimated consumption of the marking material for each print engine in the printing unit is uniform under the condition: Each of the print engines performs color printing using a plurality of color marking materials,
The consumption calculation means calculates the predicted consumption for each color marking material for each sheet,
The distribution control unit is configured to reduce the difference between the print engines in the total estimated consumption of marking materials for each color in the printing unit based on the estimated consumption of marking materials for each color for each sheet. The printing apparatus according to claim 1, wherein the sorting of the sheet is determined. A total consumption monitoring means for monitoring the total consumption of the marking material for each print engine;
The distribution control unit includes a total consumption amount of the marking material of each print engine obtained by the total consumption amount calculation unit at a printing start time of the printing unit, and each of the printing units calculated by the consumption amount calculation unit. Based on the estimated consumption of the marking material for each sheet, the sheet distribution is performed so that the estimated total consumption of the marking material of each print engine after printing of the printing unit is uniform among the print engines. The printing apparatus according to claim 1, wherein the printer is determined.   When the distribution control means detects that the difference in the total consumption of marking materials of the print engines determined by the total consumption monitoring means exceeds a predetermined allowable range, the distribution control means 3. The printing apparatus according to claim 1, wherein only a part of the print engines is selected from the one having a smaller total consumption of the marking material, and the selected print engine is caused to print a sheet of the print job. Said allocation control means, when provided with a simple distribution function for distributing sheet in order for the respective print engine in the order of the sheet, processing the print job to print multiple copies of the document 1 sheet, said consumption calculating means calculated in place of the sorting processing based on the predicted consumed amount of marking material for each sheet, the printing apparatus according to any one of claims 1 to 5, characterized in that the sorting by the simple distribution function. Said allocation control means comprises a simple distribution function for distributing sheet in order for the respective print engine in the order of the sheets, the difference between the marking material forecast consumption between each sheet of the print job is within the predetermined tolerance If, instead of the sorting processing based on the predicted consumed amount of marking material for each sheet the consumption calculation means has calculated, it claims 1-6, characterized in that performing the sorting by the simple distribution function 1 The printing apparatus according to item.

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