JP2013195868A - Image forming apparatus and image processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of reducing processing time for image formation, while suppressing a decrease in image quality.SOLUTION: An image processing apparatus 40 comprises: an image data creation unit 401; a color conversion unit 402; an image analysis unit 403; and a job information creation unit 404; and reads a plurality of documents to create job information and image information. An image formation control unit 50 of an image forming apparatus 1 comprises: a half-tone processing unit 501; a processing control unit 502; an alignment color registration control unit 503; a job information processing unit 504; and controls an image forming unit 100 including a laser exposing unit 13, a charger 12, a developing unit 14, a transfer unit 20/30, and a fixing unit 60.

Description

  The present invention relates to an image forming apparatus and an image processing apparatus.

  As the prior art described in the publication, when the number of image outputs is set and image formation is started, the input image data is read and the image ratio is calculated. Next, when one image is output and the image ratio is equal to or less than a predetermined value, a latent image is formed and developed in the entire axial direction of the photosensitive drum so as to consume a predetermined amount of toner, Replenish. If the number of output images has not reached the designated number, the above process is repeated, and if it has reached the designated number, there is an image forming apparatus that terminates image formation (see Patent Document 1).

  Further, as a conventional technique described in other publications, an image carrier, a developing device that develops an electrostatic image formed on the image carrier with toner, and a replenishing unit that replenishes toner to the developing device are provided. The image forming apparatus having a discharge port through which the toner in the developing device is discharged in accordance with the toner replenishing operation from the replenishing unit has an amount of toner commensurate with the amount of toner consumed by the developing operation of the developing device. The ratio of the first replenishment mode in which the replenishing means replenishes the developing device and the toner replenishment amount from the replenishing means to the toner consumption accompanying the developing operation of the developing device is greater than the ratio in the first replenishment mode. In addition, there is an image forming apparatus configured to have a second supply mode in which toner is supplied from the supply unit to the developing device (see Patent Document 2).

  As another prior art described in the publication, the control unit divides the dot count representing the toner consumption calculated from the image data that is the basis of the latent image formation by the latent image forming unit by the operating time of the developing device. When the value is less than B, it is determined whether the density recovery mode is set to on or off. If it is determined that it is set to on, the density recovery mode is executed to form a solid black image, and the deteriorated toner is discharged out of the copier. When it is determined to be off, a display indicating that the density recovery mode should be set is displayed on the display panel. There is an image forming apparatus that receives the display and designates the density recovery mode by the user to form the black solid image by executing the density recovery mode and discharge the deteriorated toner outside the copying machine (Patent Document 3). reference).

JP 09-034243 A JP 2006-343647 A JP 2010-085859 A

  An object of the present invention is to provide an image forming apparatus and the like that can reduce the processing time of image formation while suppressing deterioration in image quality.

According to the first aspect of the present invention, the electrostatic latent image formed on the image carrier is developed with a developer and transferred to a recording material to form an image, and the image formation is performed collectively. Requirement information that defines requirements for image formation for a plurality of documents in one unit of work and image information that defines an image for each document of the plurality of documents are input to the requirement information. An image forming unit including: an image forming control unit configured to determine whether or not to change a condition for adjusting an image quality of an image formed in the image forming unit from a predetermined condition based on the condition; Device.
According to a second aspect of the present invention, the requirement information includes an image density that is a ratio of an area occupied by the developer to the recording material in each of the plurality of documents, and adjusts the image quality. The condition is a condition for supplying the developer, and the image formation control unit determines a predetermined number of documents having an image density equal to or lower than a predetermined image density based on the image density in the requirement information. 2. The image forming apparatus according to claim 1, wherein when it is determined to be continuous, the image forming apparatus is changed to a condition different from a condition for supplying a predetermined developer corresponding to the image density.
According to a third aspect of the present invention, the requirement information includes a division of the work division or a division having different requirements for image formation on the plurality of documents, and the condition for adjusting the image quality is for adjusting the image quality. At the scheduled timing, the image formation control unit determines that the number of documents to be processed with the image quality adjusted at the timing based on the separation in the requirement information is equal to or less than a predetermined number. In this case, the image forming apparatus according to claim 1, wherein the image quality is not adjusted at the timing.
The invention according to claim 4 reads a plurality of documents in one unit of work for collectively performing image formation, extracts requirement information that defines requirements for image formation on the plurality of documents, An image processing apparatus includes: a requirement information generation unit that outputs; and an image information generation unit that extracts and outputs image information that defines an image of each of the plurality of documents.
According to a fifth aspect of the present invention, the requirement information includes an image density that is a ratio of an area occupied by a developer to a recording material on which an image is formed in each of the plurality of documents. The image processing apparatus according to claim 4.
6. The image processing apparatus according to claim 4, wherein the requirement information includes a division of the work or a division having different requirements for image formation on the plurality of documents. It is.

According to the first aspect of the present invention, it is possible to shorten the processing time for image formation while suppressing deterioration in image quality as compared with the case where requirement information is not used.
According to the second aspect of the present invention, it is possible to suppress frequent image quality adjustment as compared with the case where the present configuration is not provided.
According to the third aspect of the present invention, it is possible to suppress fluctuations in image quality in one unit of work as compared with a case where this configuration is not provided.
According to the fourth aspect of the present invention, compared with the case where the requirement information is not output, the image forming apparatus can suppress the deterioration of the image quality and can shorten the image forming processing time.
According to the invention of claim 5, frequent image quality adjustment can be suppressed as compared with the case where this configuration is not provided.
According to the sixth aspect of the present invention, it is possible to suppress fluctuations in image quality in one unit of work as compared with a case where this configuration is not provided.

FIG. 2 is a diagram illustrating a schematic configuration of an image forming apparatus to which the exemplary embodiment is applied and a relationship between the image forming apparatus and the image processing apparatus. It is a figure explaining the relationship between an image forming apparatus and an image processing apparatus by a functional block. 10 is a flowchart for explaining a method by which the image forming control unit controls the image forming unit based on the number of documents as job information. FIG. 6 is a diagram illustrating a case where an image formation control unit controls an image formation unit based on the number of documents as job information. It is a figure explaining the case where image quality adjustment is performed at a predetermined image quality adjustment interval. FIG. 6 is a diagram illustrating a case where the temperature of the fixing unit is controlled so as to reduce a change in image quality before and after image quality adjustment, and a case where the temperature is not controlled. 10 is a flowchart for explaining a method of controlling image quality adjustment timing corresponding to a case where papers of different paper quality (coated paper and uncoated paper) coexist. It is a figure explaining the image quality adjustment timing control corresponding to the case where paper of different paper quality (coated paper and non-coated paper) coexists. 6 is a flowchart illustrating a method for controlling parameters of an image forming unit based on image density information. It is a figure explaining the case where the parameter of an image formation part is controlled based on image density information. FIG. 6 is a diagram illustrating a case where the amount of toner supply is not increased beyond the amount necessary for image formation.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary. Also, the drawings used are used to describe the present embodiment, and do not represent the actual size.

[Image forming apparatus 1 and image processing apparatus 40]
FIG. 1 is a diagram illustrating an example of the configuration of the image forming apparatus 1 to which the exemplary embodiment is applied and the relationship between the image forming apparatus 1 and the image processing apparatus 40. The image forming apparatus 1 shown here will be described by taking an intermediate transfer method generally called a tandem type as an example.
The image forming apparatus 1 illustrated in FIG. 1 includes a plurality of image forming units 10Y, 10M, 10C, and 10K that form toner images of respective color components by an electrophotographic method as a toner image forming unit. Next, as a transfer unit, a primary transfer unit 20 that sequentially transfers (primary transfer) each color component toner image formed by each of the image forming units 10Y, 10M, 10C, and 10K to an intermediate transfer belt (image holding member) 15; There is a secondary transfer unit 30 that collectively transfers (secondary transfer) the superimposed toner image transferred onto the transfer belt 15 onto a sheet of recording material (recording sheet). Further, the image forming apparatus includes a fixing unit 60 that fixes the second-transferred image on a sheet as a fixing unit. The image forming control unit 50 controls the operation of each device (each unit).

As shown in FIG. 1, each of the image forming units 10Y, 10M, 10C, and 10K includes a photosensitive drum 11 that rotates in the direction of arrow A, a charger 12 that charges the photosensitive drum 11, and a photosensitive drum 11. A laser exposure device 13 for writing an electrostatic latent image (in FIG. 1, an exposure beam is indicated by a symbol Bm) and each color component toner is accommodated, and the electrostatic latent image on the photosensitive drum 11 is visualized with toner. A developing unit 14 and a potential sensor 18 that detects the charge amount of the photosensitive drum 11 are included.
Further, a primary transfer roll 16 that transfers each color component toner image formed on the photosensitive drum 11 to the intermediate transfer belt 15 by the primary transfer unit 20, a drum cleaner 17 that removes residual toner on the photosensitive drum 11, and Have These image forming units 10Y, 10M, 10C, and 10K are linearly arranged in the order of yellow (Y), magenta (M), cyan (C), and black (K) from the upstream side of the intermediate transfer belt 15. Yes.

  The developing device 14 contains a two-component developer (hereinafter referred to as a developer) containing a nonmagnetic toner (nonmagnetic toner) and a magnetic carrier (magnetic carrier). In the developing device 14, the developer is agitated, the toner and the carrier are mixed, and a charge is imparted to the toner by rubbing and rubbing. Then, in the developing unit 14, the toner is replaced in the process where the consumed toner is replenished and stirred.

  The intermediate transfer belt 15 is circulated and driven in the direction of arrow B shown in FIG. As various rolls, a drive roll 31 that circulates and drives the intermediate transfer belt 15, a support roll 32 that supports the intermediate transfer belt 15, a tension roll 33 that applies tension to the intermediate transfer belt 15 to prevent meandering, and a secondary transfer unit. 30 and a cleaning backup roll 34 provided in a cleaning section that scrapes off residual toner on the intermediate transfer belt 15.

  The primary transfer unit 20 includes a primary transfer roll 16 that faces the photosensitive drum 11 with the intermediate transfer belt 15 interposed therebetween. A voltage (primary transfer bias) having a polarity opposite to the charging polarity (minus polarity) of the toner is applied to the primary transfer roll 16, and the toner images on the photosensitive drums 11 are sequentially electrostatically attracted to the intermediate transfer belt 15, A superimposed toner image is formed on the transfer belt 15.

  The secondary transfer unit 30 includes a secondary transfer roll 22 disposed on the toner image holding surface side of the intermediate transfer belt 15 and a backup roll 25 disposed on the back surface side of the intermediate transfer belt 15 as a counter electrode of the secondary transfer roll 22. And a metal power supply roll 26 that is disposed in contact with the backup roll 25 and applies a secondary transfer bias.

  An intermediate transfer belt cleaner 35 for removing residual toner and paper dust on the intermediate transfer belt 15 after the secondary transfer is provided on the downstream side of the secondary transfer portion 30 of the intermediate transfer belt 15 so as to be contactable and separable. A reference sensor (home position sensor) 42 that generates a reference signal for taking an image forming timing in each of the image forming units 10Y, 10M, 10C, and 10K is disposed upstream of the yellow image forming unit 10Y. Further, an image density sensor 43 for adjusting image quality is disposed on the downstream side of the black image forming unit 10K. The reference sensor 42 recognizes a mark provided on the back side of the intermediate transfer belt 15 and generates a reference signal. In response to an instruction from the image formation control unit 50 based on the recognition of the reference signal, each image forming unit 10Y, 10M, 10C and 10K start image formation. Further, the image density sensor 43 irradiates the image density evaluation toner image formed on the intermediate transfer belt 15 with light, and receives the reflected light with a light receiving element. Evaluate the concentration.

In the present embodiment, as a recording paper transport system, a paper storage unit 70 that stores paper, a pick-up roll 51 that picks up and transports paper in the paper storage unit 70, a transport roll 52 that transports paper, and paper A transport path 53 that feeds the secondary transfer unit 30, a transport belt 55 that transports the paper secondarily transferred by the secondary transfer roll 22 to the fixing unit 60, and a fixing inlet guide 56 that guides the paper to the fixing unit 60. Have.
An image detection sensor 44 that detects an image formed on the sheet is provided on the exit side of the fixing unit 60.

The image detection sensor 44 uses, for example, 928 kinds of test images (color patches) including halftones (halftones) of Y, M, C, and K as colors of CIEL ^* a ^* b ^* color system. Evaluate by etc. Thereby, the color stability in the image forming apparatus 1, that is, the color difference ΔE can be obtained to evaluate the color stability.
Hereinafter, as a specific example, the maximum value, average value, and / or 95% tile value of the color difference ΔE from the value (initial value) at the time of color calibration (calibration) in 928 types of color patches are shown. Yes.

  The fixing unit 60 includes a fixing belt 61 heated by a lamp or the like, and a pressure roll 62 provided to face the fixing belt 61 and provided to press the fixing belt 61. As the paper passes between the fixing belt 61 and the pressure roll 62 (nip portion) each heated to a predetermined temperature, the toner is fixed (fixed) to the paper by heat and pressure. . The pressure roll 62 may not be heated.

  On the other hand, the image processing device 40 is connected to, for example, a personal computer (PC) 2 or an image reading device (scanner) 3, and performs predetermined processing on image data received from these, and stores image information and requirement information. It is processed into job information as an example and transmitted to the image forming control unit 50 of the image forming apparatus 1. Here, a plurality of PCs 2 and image reading apparatuses 3 may be connected to the image processing apparatus 40. Further, there may be a plurality of image forming apparatuses 1 to which the image processing apparatus 40 transmits image information and job information. That is, the image processing device 40 may operate as a print server, receives image data from a plurality of PCs 2 and image reading devices 3, generates image information and job information based on the image data, The data is transmitted to a plurality of image forming apparatuses 1.

Next, a basic image forming process by the image forming apparatus 1 and the image processing apparatus 40 will be described.
Image data output from the PC 2 or the image reading device 3 is input to the image processing device 40. The image processing device 40 generates job information and image information based on the image data. Then, the image processing apparatus 40 transmits job information and image information to the image formation control unit 50 of the image forming apparatus 1. The generation of job information and image information from the image data by the image processing apparatus 40 will be described later.

  The image formation control unit 50 controls the laser exposure device 13, the charger 12, the developing device 14, the primary transfer unit 20, the secondary transfer unit 30, and the fixing unit 60 based on the received job information and image information. Hereinafter, operations of the laser exposure device 13, the charger 12, the developing device 14, the primary transfer unit 20, the secondary transfer unit 30, and the fixing unit 60 controlled by the image forming control unit 50 will be described.

  The laser exposure device 13 irradiates, for example, an exposure beam Bm emitted from a semiconductor laser to the respective photosensitive drums 11 of the image forming units 10Y, 10M, 10C, and 10K according to the input color material gradation data. After the surfaces of the photosensitive drums 11 of the image forming units 10Y, 10M, 10C, and 10K are charged by the charger 12, the surfaces are scanned and exposed by the laser exposure unit 13 to form an electrostatic latent image. The formed electrostatic latent image is developed as a toner image of each color of Y, M, C, and K by the developing device 14 in each of the image forming units 10Y, 10M, 10C, and 10K.

  Next, the toner image formed on the photoconductive drum 11 is applied to the base material of the intermediate transfer belt 15 by the primary transfer roll 16 in the primary transfer unit 20 where the photoconductive drums 11 and the intermediate transfer belt 15 are in contact with each other. Then, a voltage (primary transfer bias) having a polarity opposite to the charging polarity (minus polarity) of the toner is applied, and the toner image is sequentially superimposed on the surface of the intermediate transfer belt 15 to perform primary transfer.

  After the toner images are sequentially primary transferred onto the surface of the intermediate transfer belt 15, the intermediate transfer belt 15 moves and conveys the toner image to the secondary transfer unit 30. The recording paper conveyance system rotates the pickup roll 51 in accordance with the timing of conveying the toner image to the secondary transfer unit 30 and supplies the paper from the paper storage unit 70. The paper supplied by the pickup roll 51 is conveyed by the conveyance roll 52 and reaches the secondary transfer unit 30 via the conveyance path 53. Before reaching the secondary transfer unit 30, the sheet is temporarily stopped, and a registration roll (not shown) is rotated in accordance with the movement timing of the intermediate transfer belt 15 holding the toner image. Align with the position of.

  In the secondary transfer unit 30, the secondary transfer roll 22 is pressed against the backup roll 25 via the intermediate transfer belt 15, and the unfixed toner image held on the intermediate transfer belt 15 is transferred to the intermediate transfer belt 15 and the secondary transfer belt 15. The electrostatic transfer is collectively performed on the paper sandwiched between the rolls 22.

Thereafter, the sheet on which the toner image has been electrostatically transferred is peeled off from the intermediate transfer belt 15 by the secondary transfer roll 22 and conveyed as it is, and is conveyed to a conveyance belt 55 provided downstream of the secondary transfer roll 22 in the recording sheet conveyance direction. To do. The conveyance belt 55 conveys the sheet to the fixing unit 60. The fixing unit 60 processes the unfixed toner image on the paper with heat and pressure and fixes it on the paper. The sheet on which the fixed image has been formed is conveyed to a discharge unit of the image forming apparatus.
After the transfer to the paper is completed, the residual toner remaining on the intermediate transfer belt 15 is conveyed to the cleaning unit as the intermediate transfer belt 15 is circulated, and the intermediate transfer is performed by the cleaning backup roll 34 and the intermediate transfer belt cleaner 35. Remove from the belt 15.

  FIG. 2 is a diagram illustrating the relationship between the image forming apparatus 1 and the image processing apparatus 40 using functional blocks. In FIG. 2, the image forming apparatus 1 is divided into an image forming control unit 50 and an image forming unit 100. Here, the image forming unit 100 is the same as the image forming apparatus 1 shown in FIG. 1 except for the image forming control unit 50, and includes a charger 12, a laser exposure unit 13, a developing unit 14, and a primary transfer unit 20. The secondary transfer unit 30, the fixing unit 60, and the like. The primary transfer unit 20 and the secondary transfer unit 30 are shown as transfer units 20/30.

  The image forming control unit 50 of the image forming apparatus 1 includes a halftone processing unit 501, a process control unit 502, an alignment / color registration control unit 503, and a job information processing unit 504, and controls the image forming unit 100. The functions of the halftone processing unit 501, the process control unit 502, the alignment / color registration control unit 503, and the job information processing unit 504 will be described later.

  On the other hand, the image processing apparatus 40 includes an image data generation unit 401, a color conversion unit 402, an image analysis unit 403, and a job information generation unit 404. Here, the image data generation unit 401 and the color conversion unit 402 are examples of an image information generation unit, and the image analysis unit 403 and the job information generation unit 404 are examples of a requirement information generation unit.

Now, operations of the image processing device 40 and the image formation control unit 50 will be described.
First, the operation (processing) of the image processing apparatus 40 will be described.
A document is input to the image data generation unit 401 and the job information generation unit 404 of the image processing device 40 from the PC 2, the image reading device 3, or the like. In the present embodiment, the image processing apparatus 40 can input and store a plurality of originals. As an example, it is assumed that the A3 size is 127 sheets (indicated as N (an integer of 1 or more) in FIG. 2).

Then, the image data generation unit 401 converts (rasterizes) a coded document such as a page description language (PDL: page description language) into raster image data, and transmits the raster image data to the color conversion unit 402.
A color conversion unit 402 performs color conversion of raster image data. For example, image data expressed in the RGB color system is first converted into the CIEL ^* a ^* b ^* color system. Next, the CIEL ^* a ^* b ^* color system is converted to the YMCK color system. Thus, image information that can be processed by each of the image forming units 10Y, 10M, 10C, and 10K is obtained.
In addition, the color conversion unit 402 may perform gradation correction (gradation correction). Then, the image information of the YMCK color system is transmitted to the halftone processing unit 501 of the image formation control unit 50.
Here, since the information (image data) transmitted from the color conversion unit 402 to the halftone processing unit 501 is data corresponding to each image of the document, it is expressed as image information.

  Note that the image analysis unit 403 calculates the ratio (image density) of the area occupied by the image (toner) on the paper from the raster image data when the image data generation unit 401 converts the document into raster data. The image density is also called area coverage.

On the other hand, the job information generation unit 404 acquires job information from the input document.
As described above, in the present embodiment, a plurality of documents are input. Therefore, the job information generation unit 404 extracts requirements for image formation such as the number of originals for each job (work), the number of copies, the printing surface (front and back), color mode / monochrome mode, and the like. In other words, these requirements make it possible to know where the job ends and where the number of copies ends (group break). In addition, paper type information which is a requirement for image formation such as the type of paper on which an image is formed (separated from coated paper / non-coated paper, basis weight, thickness) and the like is extracted.
Then, the document / job information generation unit 404 combines the information such as the number of documents for each job and the paper type information with the above-described information regarding the image density (image density information) as job information, and outputs the image in the image forming apparatus 1. The information is transmitted to the job information processing unit 504 of the formation control unit 50.

Next, the operation (processing) of the image formation control unit 50 in the image forming apparatus 1 will be described.
The halftone processing unit 501 of the image formation control unit 50 receives the YMCK color system image information transmitted from the color conversion unit 402 of the image processing apparatus 40 and generates halftone processing, that is, a screen pattern. Along with this, the definition is corrected so that the definition is not impaired.

  The job information processing unit 504 uses the above job information (information such as the number of documents, paper type information, and image density information) as information that can be used by the image formation control unit 50 to control the image forming unit 100. Process to process. For example, the information is processed into information specifying the last page of the job, the last page of each part, the front page of the paper, and the back page.

  Further, the process control unit 502 of the image formation control unit 50 is based on the information about the job from the job information processing unit 504 and the information about the image from the halftone processing unit 501, and the charger 12 and the developing unit 14. The potential applied to the is controlled. In addition, the alignment / color registration control unit 503 corrects an image position shift (alignment) and a position shift of each color in the color image.

  As described above, in the present embodiment, the flow of image information transmitted to the image formation control unit 50 of the image forming apparatus 1 through the image data generation unit 401 and the color conversion unit 402 in the image processing apparatus 40, There is a flow of job information transmitted to the image formation control unit 50 of the image forming apparatus 1 via the job information generation unit 404 in the image processing apparatus 40.

In the present embodiment, the image processing apparatus 40 can store a plurality of originals, for example, 127 sheets. Therefore, job information (number of originals, number of copies, printing surface (front and back), information on color mode / monochrome mode, paper type information, image density information) for each job up to 127 sheets ahead is known. Therefore, the image processing apparatus 40 can transmit job information to the image formation control unit 50 before the image formation control unit 50 starts image formation. As a result, the image forming control unit 50 can set each parameter for controlling the image forming unit 100 corresponding to the image forming to be performed from now on.
That is, in the present embodiment, so-called advance control (feed forward control) is made possible by prefetching a plurality of documents and acquiring job information. Thus, the image formation control unit 50 controls the parameters of the image forming unit 100 in response to the image formation to be performed in the future, thereby suppressing the image forming process time and suppressing the image formation processing time. ing.
Details will be described below.

(Image quality adjustment in the image forming apparatus 1)
Here, the image adjustment in the image forming apparatus 1 will be described.
The image forming apparatus 1 counts the image density value (cumulative image density value) obtained by accumulating the image density every time the original image is formed, and is consumed when the accumulated image density value exceeds a predetermined value. Toner is replenished to suppress fluctuations in image density.

However, if the toner stays in the developing device 14 for a long time, the external additive externally added to the toner is embedded in or released from the toner by agitation, and developability and transferability deteriorate ( Toner deterioration).
Therefore, in the image forming apparatus 1, when the number of processed images reaches a predetermined number, the job is interrupted, toner refresh to replace the deteriorated toner, image density fluctuation, shift between colors, image formation, and the like. The image quality adjustment for adjusting the image quality, such as the shift of the position (registration), is performed.
The image quality adjustment is performed, for example, at a timing when 3600 images have been formed on A4 paper. Therefore, it is called an image quality adjustment cycle.

Further, when a document having an extremely low image density is continuously formed (processed), the amount of toner consumption is small and the replacement with new toner is small. For this reason, when the charge amount of the toner is increased by the stirring in the developing unit 14 or the external additive externally added to the toner is embedded in or released from the toner, the adhesion force of the toner is increased. As the charge amount increases, the image density decreases. Further, when the adhesion force of the toner is increased, graininess appears in the image in the transfer process, and printing unevenness (motor) occurs. Therefore, the control of the bias potential applied to the developing device 14 is combined to suppress the deterioration of the image quality even when the charge amount increases.
Further, by adding a dummy toner image (toner band) to the gap (inter-image portion) between the toner image on the intermediate transfer belt 15 and consuming the toner, the amount of toner supply can be increased. Has been done. However, toner consumption by the toner band is limited.
Therefore, the image formation control unit 50 monitors the formed image and adds an image quality adjustment such as interrupting the job and replacing the toner when an abnormality is found.

  Further, when the temperature in the image forming apparatus 1 changes by 5 ° C., the intermediate transfer belt 15 expands and contracts, and a positional shift occurs between the colors. Even when such a temperature change is detected, image quality adjustment is performed to adjust the position (registration).

  During these image quality adjustment periods, the sheet does not pass through the fixing unit 60, so that the pressing of the nip formed by the fixing belt 61 and the pressure roll 62 is released. As a result, the temperature of the heated fixing belt 61 rapidly increases. This is because the paper continuously passes through the fixing unit 60 when the job is continued. In this state, the fixing unit 60 is controlled such that the nip portion formed by the fixing belt 61 and the pressure roll 62 pressed against the fixing belt 61 is maintained at a predetermined temperature. However, when the image quality adjustment is performed, the sheet does not pass through the fixing unit 60, and heat is not taken away by the sheet, so that the temperature of the nip portion increases. The temperature of the nip portion is highest immediately after the job is resumed. For this reason, a sheet that has passed through the fixing unit 60 immediately after the job is resumed restarts image formation due to a difference in temperature of the nip portion in the fixing unit 60 with respect to a sheet that has passed through the fixing unit 60 immediately before the job is interrupted. Immediately after, the density of the formed image is increased. For this reason, the image quality fluctuates before and after the image quality adjustment.

Furthermore, if image quality adjustment is performed during job execution, the job is interrupted. For this reason, the time required for the job becomes longer than when the image quality adjustment is not executed.
On the other hand, if the image quality adjustment is not performed, the image quality deteriorates due to the deterioration of developability and transferability and the increase in the charge amount.

  That is, in order to shorten the time required for a job, it is preferable not to perform image quality adjustment during execution of the job. Therefore, in the image forming apparatus 1 according to the present embodiment, the image processing apparatus 40 acquires job information obtained by pre-reading a plurality of originals, and suppresses the execution of image quality adjustment during execution of the job or the image quality. Suppresses fluctuations in image quality before and after adjustment.

(Control of image quality adjustment timing based on the number of documents)
A case where the image forming unit 100 is controlled based on job information, for example, the number of originals will be described.
As described above, the image quality adjustment is executed when the number of processed images reaches the predetermined number. However, the image quality adjustment does not necessarily have to be performed when the predetermined number of images is reached.
For example, even if the image quality adjustment is not executed at the scheduled timing, the difference between the image quality in the image formation (processing) immediately before the scheduled timing and the image quality in the immediately subsequent image formation (processing) is small. Therefore, when the number of originals to be imaged (processed) after image quality adjustment is smaller than the number of originals to be imaged (processed) during image quality adjustment before and after, all originals are imaged (processed). Even if the image quality adjustment is performed after that, it is considered that the degradation of the image quality in the original image formed (processed) after the scheduled image quality adjustment timing is small and within an allowable range.
Therefore, in the present embodiment, the image formation control unit 50 calculates the number of originals to be imaged (processed) after the image quality adjustment is scheduled from the job information transmitted by the image processing apparatus 40 in advance. If it is equal to or less than the predetermined threshold value Tc, the image formation (processing) of the document is performed first without performing image quality adjustment at the scheduled timing.
Accordingly, since the image quality adjustment is not executed during the job, the time required for the job can be shortened. In addition, the continuity of image quality is maintained.

FIG. 3 is a flowchart for explaining a method in which the image forming control unit 50 controls the image forming unit 100 based on the number of documents as job information. Here, the operation of the image formation control unit 50 will be described.
The image formation control unit 50 receives job information from the image processing apparatus 40 (step 1). Next, from the job information, the number of documents Pc to be subjected to image formation (processing) after the scheduled image quality adjustment (scheduled timing) is calculated (step 2). Then, it is determined whether or not the number of documents Pc is equal to or less than a predetermined threshold value Tc (step 3). If an affirmative (Yes) determination is made in step 3, image formation (processing) of the document is performed without performing image quality adjustment at the scheduled timing (step 4). Then, after image formation (job) is completed for the original, image quality adjustment is executed (step 5).

  On the other hand, if a negative (No) determination is made in step 3, image quality adjustment is performed at the scheduled timing (step 6). Then, image formation is performed on the remaining document (step 7).

FIG. 4 is a diagram illustrating a case where the image forming control unit 50 controls the image forming unit 100 based on the number of originals as job information. 4A shows the timing of image quality adjustment, FIG. 4B shows the change in image density, and FIG. 4C shows a specific example of the change in color difference ΔE.
Assume that the timing advances from timing T1 to timing T4 (see FIG. 4A).

As shown in FIG. 4A, the timing from the timing T1 to the timing T2 is a predetermined image quality adjustment interval (image quality adjustment interval). In the example shown before, there are 3600 sheets in the A4 document size.
Then, it is assumed that the job is started at timing T2. At this time, the previous image quality adjustment is performed at timing T1. The next image quality adjustment is scheduled to be performed at timing T3. That is, the timing T3 becomes the scheduled timing (scheduled timing T3).

Now, it is assumed that the number of documents is 1043, and the remaining number of documents Pc is 100 at the scheduled timing T3. That is, the scheduled timing T3 is the time when the image formation (processing) of the 943rd original is performed.
In the present embodiment, the image processing apparatus 40 constantly prefetches 127 originals and transmits job information to the image formation control unit 50. Therefore, the image processing apparatus 40 transmits to the image formation control unit 50 that the number of originals Pc to be image-formed (processed) after the timing T3 is 100 at the time of reading the last original of this job. Here, the threshold value Tc is 110 sheets, which is smaller than 127 sheets of the pre-read document. The 110 sheets with the threshold value Tc are fewer than the 3600 sheets on which image formation (processing) is performed during image quality adjustment.
The reason why the threshold value Tc is set to be smaller than the number of documents to be pre-read is to acquire the number of images to be formed (processed) after timing T3 when the last document is read. If the threshold value Tc is larger than the number of documents to be pre-read, it can be considered that the image formation control unit 50 has already executed image quality adjustment when the image processing apparatus 40 has read the last document. is there.

  Accordingly, the image formation control unit 50 determines that the number of originals Pc to be imaged (processed) after the timing T3 is 100 and is equal to or less than the threshold value Tc, and performs image quality adjustment at the timing T3. However, image formation is continued for the original as it is. Then, image quality adjustment is performed at timing T4 when the job ends. In this case, the job is not interrupted during execution. Therefore, the time required for the job is shorter than that required for image quality adjustment.

As shown in FIG. 4B, the image density gradually decreases from the timing T1 when the image quality adjustment has been performed before the next image quality adjustment. When the image quality adjustment is not performed at the timing T3, the image density is decreased after the timing T3 as compared with the case where the image quality adjustment is performed at the timing T3.
However, as described above, the number of documents to be imaged (processed) after the timing T3 is smaller than the number of documents to be imaged (processed) during the preceding and following image quality adjustments. The decrease of the is small and acceptable.

  And as shown in FIG.4 (c), color difference (DELTA) E does not show a big difference before and after timing T3 also about a maximum value, a 95% tile value, and an average value.

  As described above, by not performing the image quality adjustment at the timing T3 where the image quality adjustment is scheduled, the time required for the job can be shortened and the continuity of the image density and the color difference ΔE can be maintained.

  FIG. 5 is a diagram illustrating a case where image quality adjustment is executed at a predetermined image quality adjustment interval. Similar to FIG. 4, FIG. 5A shows the timing of image quality adjustment, FIG. 5B shows the change in image density, and FIG. 5C shows a specific example of the change in color difference ΔE. .

In FIG. 5A, as in FIG. 4, the previous image quality adjustment is at timing T1, and the next image quality adjustment is at timing T3.
It is assumed that the job is started at the timing T2. This job is assumed to have 100 remaining documents at timing T3.
However, since the image quality adjustment is performed at a predetermined image quality adjustment interval, the next image quality adjustment is performed at timing T3. For this reason, the time required to complete the image formation (processing) of the remaining 100 sheets is delayed by the time required for image quality adjustment. That is, since the job is interrupted during execution of the job, the time required for the job becomes long.

  As shown in FIG. 5B, at the timing T3 when the image quality adjustment is performed, the image density rapidly changes from the light side to the dark side.

  Similarly, as shown in FIG. 5C, the color difference ΔE shows a large difference between the maximum value, the 95% tile value, and the average value before and after the timing T3, that is, between the 943rd sheet and the 944th sheet. . That is, before and after the timing T3, the maximum color difference ΔE increases from 2.8 to 6.2, the 95% tile value from 2 to 4.6, and the average value from 1 to 2.

  As described above, when image quality adjustment is performed at the timing T3 during execution of a job, the required time of the job becomes long and productivity decreases, and the continuity of the image density and color difference ΔE of the formed image is lost. End up.

In the present embodiment, the image processing apparatus 40 prefetches a document and continuously transmits job information to the image formation control unit 50. Therefore, if the number of documents to be imaged (processed) after the scheduled image quality adjustment timing is less than the threshold value Tc, the image formation control unit 50 may set the image quality adjustment timing to be extended after the job is completed. it can.
By doing so, the time required for the job is shortened and the continuity of the image density and the color difference ΔE can be maintained.

The threshold value Tc may be set in consideration of image quality such as image density and color difference ΔE. That is, when the deterioration in image quality is large, the threshold value Tc may be set small.
Note that the user may be able to select whether to continue the job beyond the scheduled timing of image quality adjustment.

(Image quality adjustment based on the number of originals)
In the image quality adjustment timing control based on the above-described job information, in particular, the number of documents, image quality adjustment is executed when the number of documents Pc to be imaged (processed) after the scheduled image quality adjustment timing is equal to or less than the threshold value Tc. The image formation was continued.
On the other hand, when the job continues before and after the scheduled image quality adjustment timing, the image formation control unit 50 forms the image so that the change in the image quality (color difference ΔE) is small even if the scheduled image quality adjustment is executed. The parameters of the unit 100 may be controlled.
This method can also be applied to the case where the number of originals Pc on which an image is formed after the image quality adjustment timing is equal to or less than a threshold value Tc.

In the above description, it has been described that when the image quality adjustment is performed, the temperature of the fixing unit 60 increases and the image quality varies. Then, the temperature of the fixing unit 60 becomes the highest when the job is resumed, and thereafter, the temperature of the nip portion of the fixing unit 60 decreases as the sheet passes. And the image quality (color difference ΔE) also becomes smaller.
That is, the color difference ΔE becomes the largest when the job is resumed and then becomes smaller.

Therefore, in the present embodiment, the image forming control unit 50 uses the job information from the image processing device 40 in the fixing unit 60 immediately after the image quality adjustment when the document continues before and after the scheduled image quality adjustment timing. The temperature of the nip part is set to a low value and is controlled so as to return to the original value upon restart.
As a result, even if the scheduled image quality adjustment is performed, the change in image quality before and after the image quality adjustment can be reduced.

FIG. 6 is a diagram for explaining the case where the temperature of the fixing unit 60 is controlled to reduce the change in image quality before and after the image quality adjustment, and the case where the temperature is not controlled. 6A shows the change of the color difference ΔE when the temperature of the fixing unit 60 is controlled after the timing of image quality adjustment, and FIG. 6B shows the color difference ΔE when the temperature of the fixing unit 60 is not controlled. It is the figure which showed the change of each with the specific example.
4 and 5, the image quality adjustment is performed immediately after the 943rd image is formed (processed).

  FIG. 6A shows a case where control is performed so that the temperature of the fixing unit 60 after image quality adjustment is lowered. Since the image quality adjustment is performed, there is a difference in the color difference ΔE (95% tile value) before and after the image quality adjustment, that is, between the 943rd sheet and the 944th sheet. However, the color difference ΔE (95% tile value) is 0.8 between the 944th sheet immediately after the image quality adjustment and the 950th sheet in which the variation of the color difference ΔE has subsided.

  On the other hand, FIG. 6B shows a case where the temperature of the fixing unit 60 after image quality adjustment is not controlled. In this case, compared with FIG. 6A, the variation of the color difference ΔE (95% tile value) immediately after the image quality adjustment is large. The color difference ΔE (95% tile value) between the 944th sheet and the 950th sheet in which the variation of the color difference ΔE has settled is 2.04. FIG. 6B is an enlarged view of the 940th sheet to the 955th sheet in FIG. 5C.

  As described above, when the temperature of the nip portion in the fixing unit 60 is controlled to be low when the job is resumed, the color difference ΔE (95% tile value) immediately after the image quality adjustment is not controlled to be low. .04 to 0.8. That is, control can be performed so as not to impair the continuity of image quality.

  As can be seen from FIG. 6B, the variation in the color difference ΔE immediately after the image quality adjustment is seen in the image formation (processing) of the 944th sheet to the 949th sheet, and the variation is small from the 950th sheet. It has become. Accordingly, the temperature of the fixing belt 61 may be controlled during this period (corresponding to the image formation (processing) of six sheets).

  Although the temperature of the nip portion of the fixing unit 60 is controlled here, the exposure amount control in the laser exposure unit 13, the charging potential in the charging unit 12, the development potential in the developing unit 14, the primary transfer unit 20 or the secondary transfer unit. Other parameters in the image forming unit 100 such as a transfer potential in the unit 30 may be controlled.

(Control of image quality adjustment timing based on paper type information)
An example in which the image forming control unit 50 controls the image forming unit 100 when different types of paper are mixed based on the paper type information in the job information will be described.
Paper quality includes the presence or absence of surface treatment (coated paper, uncoated paper), weight per unit area (basis weight), thickness, and the like. Coated paper is a paper that smoothens the surface by applying special chemicals to the surface of high-quality paper or medium-quality paper, and can obtain better print quality than uncoated paper (high-quality paper or medium-quality paper). That is.

  In image formation in the image forming apparatus 1, for example, when creating a booklet, different paper quality sheets may be used for the front cover / back cover and the main body. When switching to a paper of a different paper quality, the image formation control unit 50 suppresses fluctuations in image quality by adjusting the image quality such as adjusting the amount of developer supplied. For example, as described above, the smoothness of the surface differs between coated paper and uncoated paper. Therefore, when the same developer is supplied, the image density of the coated paper becomes higher than that of the non-coated paper. Therefore, image quality adjustment for changing the supply amount of developer is performed at the timing of switching from uncoated paper to coated paper.

  For this reason, when using different paper quality for the front cover / back cover and the main body, if images of the front cover, main body, back cover, etc. are continuously formed, the timing of switching between the front cover and the main body and the timing between the main body and the back cover Image quality adjustment is performed at the timing of switching. In an extreme case, when the paper quality is different for each sheet, the image quality adjustment is performed for each sheet. Further, if the front cover / back cover and the main body are separately formed (printed), bookbinding becomes complicated.

  In the present embodiment, the execution of image quality adjustment is suppressed when different paper quality paper is set based on paper type information acquired by pre-reading a plurality of documents. This will be described below.

FIG. 7 is a flowchart for explaining a method of controlling the image quality adjustment timing corresponding to the case where papers of different paper quality (coated paper and non-coated paper) coexist. Here again, the operation of the image forming control unit 50 will be described.
The image formation control unit 50 receives the paper type information from the image processing apparatus 40 (step 11). Then, when papers having different paper qualities are designated, it is determined whether or not the papers having different paper qualities are arranged in the order of paper quality 1, paper quality 2, and paper quality 1 (step 12). That is, it is determined whether one paper quality (paper quality 2) is sandwiched between the other paper quality (paper quality 1).
Hereinafter, a case where an affirmative (Yes) determination is made in Step 12 will be described, and a case where a negative (No) determination is made will be described later.

If the determination in step 12 is affirmative (Yes), the number of originals Pp of paper quality 2 is calculated from the paper type information of the job information. Then, it is determined whether or not the number of documents Pp is equal to or less than a predetermined threshold value Tp (step 14). If the determination in step 14 is affirmative (Yes), document image formation (processing) is performed without adjusting image quality at the timing when the paper quality changes.
On the other hand, if a negative (No) determination is made in step 14, image quality adjustment is performed at the timing when the paper quality changes, and image formation (processing) of the document is performed.

  Even when a negative (No) determination is made in step 12, image quality adjustment is performed at the timing when the paper quality changes, and image formation (processing) of the document is performed.

As described above, in the present embodiment, the image processing apparatus 40 prefetches a document and transmits sheet type information to the image formation control unit 50. Therefore, when the number of images to be formed on different paper qualities is less than the predetermined threshold value Tp, the image formation control unit 50 shortens the job processing time by not adjusting the image quality at the timing when the paper quality changes. it can.
The threshold value Tp may be set in consideration of a change in image quality due to different paper quality.

FIG. 8 is a diagram for explaining image quality adjustment timing control corresponding to a case where papers of different paper quality (coated paper and non-coated paper) coexist. FIGS. 8A1 and 8A2 illustrate image quality adjustment timing control in the present embodiment, and FIGS. 8B1 and 8B2 illustrate a case where image quality adjustment is performed at a timing when the paper quality is changed. .
Assume that the timing advances from timing T5 to timing T8 (see FIG. 8A1).

In FIG. 8A1, the paper quality 1 (uncoated paper) started at the timing T5 is followed by the paper quality 2 (coated paper) at the timing T6, and then the original paper quality 1 (uncoated) at the timing T7. Paper). The number of originals Pp for forming an image on a paper of quality 2 (coated paper) sandwiched between paper of quality 1 (uncoated paper) and paper of quality 1 (uncoated paper) is determined in advance. It is below the threshold value Tp (here, <127).
The reason why the threshold value Tp is set smaller than 127, which is the number of documents to be pre-read, is the same as in the case of the threshold value Tc.

In the present embodiment, since the image processing apparatus 40 pre-reads 127 documents, the fact that the number Pp of paper quality 2 (coated paper) is equal to or less than the threshold value Tp is used as the paper type information in the job information. To the image formation control unit 50. Therefore, the image formation control unit 50 performs both image quality adjustment for handling paper quality 2 (coated paper) at timing T6 and image quality adjustment for handling paper quality 1 (uncoated paper) at timing T7. Instead, control is performed so that image formation is performed on paper quality 2 (coated paper) using parameters corresponding to paper quality 1 (non-coated paper).
Thus, in this embodiment, time required for image quality adjustment does not enter. Therefore, the job processing time can be shortened compared to the case of adjusting the image quality.

  As shown in FIG. 8A2, when the number Pp of paper quality 2 (coated paper) exceeds the threshold value Tp from the job information, the image formation control unit 50 adjusts the image quality at timing T6. Control is performed (step 16 in FIG. 7). At this time, the job is interrupted.

On the other hand, as shown in FIG. 8B1, when the document is not prefetched, the timing T6 when the paper quality 1 (uncoated paper) is transferred to the paper quality 2 (coated paper) and the paper quality 2 (coated paper) are transferred. At the timing T7 when the paper is transferred to the paper quality 1 (uncoated paper), the image quality adjustment to the parameter corresponding to the paper quality 2 (coated paper) and the image quality to the parameter corresponding to the paper quality 1 (uncoated paper) are performed. Perform adjustments.
For this reason, since the job is interrupted at the timings T6 and T7, the processing time of the job becomes longer than when the job is not interrupted.

  FIG. 8B2 shows a case where the paper of quality 2 (coated paper) is continuous for a long time. This case is the same as FIG.

  As described above, in the present embodiment, the image formation control unit 50 prefetches a document from the image processing apparatus 40 to acquire the paper type information that is job information, and the number Pp of different paper qualities sandwiched between them. When the value is smaller than the threshold value Tp, the image formation (processing) of the document is continued without adjusting the image quality even when the paper quality is switched. This shortens the job processing time.

  Here, the non-coated paper and the coated paper having different surface smoothness have been described. However, the same applies when other specifications are different, such as when the basis weight, which is the weight of the paper per unit area, is different. And when applied when the at least one specification is the same, such as when the basis weight is the same and the surface smoothness is different, or when the smoothness is the same and the basis weight is different, the deterioration of the image quality can be further suppressed.

(Parameter control based on image density information)
As described above, when images with extremely low image density are continuously formed (processed), the amount of toner consumed is small and the replacement with new toner is small. For this reason, the toner in the developing device 14 is abnormally charged due to friction and friction due to stirring in the developing device 14. Further, when an external additive externally added to the toner is embedded in or released from the toner, the adhesion force of the toner increases. So-called toner deteriorates.
For this reason, even in the middle of a job, image adjustment including toner refresh that interrupts the job at regular intervals, consumes toner, and replenishes toner is performed. In this image adjustment, the image formation control unit 50 measures an image density cumulative value obtained by accumulating the image density of a document on which image formation has been performed, so that a document with extremely low image density is continuously formed (processed). This is performed when it is determined that the toner is charged or when the charge amount of the toner becomes higher than a predetermined value.

Even when a toner band is provided in the inter-image portion on the intermediate transfer belt 15, when an image having a very low image density is continuously formed (processed), the job is interrupted and toner refresh is performed. It will be necessary.
As described above, when image adjustment including toner refresh is performed, the job is interrupted, the time required for the job becomes longer, and the image quality (color difference ΔE and the like) varies.

  In addition, since toner consumption occurs abruptly when an extremely low-density original is continuously imaged (processed) and then a high-density original is imaged (processed), development to the developing device 14 is performed. The agent is supplied rapidly. This also causes a large variation in the color difference ΔE.

  As described above, the color difference ΔE varies when the toner consumption is low and when the toner consumption changes abruptly. Therefore, it is preferable to reduce a fluctuation in toner consumption by suppressing a state where toner consumption is low.

In the present embodiment, the image processing apparatus 40 prefetches, for example, 127 originals and transmits image density information for 127 sheets to the image formation control unit 50. Therefore, the image formation control unit 50 can know that a document having an extremely low image density is continuously formed (processed) before image formation.
Therefore, the image formation control unit 50 sets the toner supply amount so that toner refresh is not required even when an image having a very low image density is continuously formed (processed). That is, when images with extremely low image density are continuously formed (processed), a larger amount of toner than that required for image formation is supplied. By doing so, it is possible to prevent the toner from being abnormally charged due to the low consumption of the toner.

  As described above, when a document having an extremely low image density is continuously formed (processed), toner refresh may be required even if a toner band is provided in the inter image portion. Therefore, setting is made so that more toner is consumed than the amount of toner consumed by the toner band. This is because if the toner consumption is equal to or less than that in the case where the toner band is provided in the inter image portion, the toner refresh is performed in the middle of the job as in the case where the toner band is provided in the inter image portion.

FIG. 9 is a flowchart illustrating a method for controlling the parameters of the image forming unit 100 based on the image density information. Here, the operation of the image forming control unit 50 will be described.
The image formation control unit 50 receives image density information from the image processing apparatus 40 (step 21). Then, when documents having an image density lower than a predetermined image density are consecutive, the number of consecutive documents Pd is calculated (step 22). Then, it is determined whether or not the number of documents Pd is equal to or greater than a predetermined threshold value Td (step 23). If the determination in step 23 is affirmative (Yes), the developing device 14 of the image forming unit 100 is controlled so as to supply the toner supply amount to be larger than a predetermined amount (step 24).
On the other hand, if a negative (No) determination is made in step 23, image formation (processing) is continued with the previous toner supply amount.

  As described above, in the present embodiment, the image processing apparatus 40 prefetches a document and transmits image density information to the image formation control unit 50. Therefore, the image formation control unit 50 increases the supply amount of toner when a document having an extremely low image density is continuously formed (processed) in a number greater than a predetermined threshold value Td. Control so that toner refresh does not occur. Thus, the job is not interrupted for toner refresh, and the job processing time can be shortened. In addition, as will be described later, it is possible to suppress deterioration in image quality.

FIG. 10 is a diagram illustrating a case where the parameters of the image forming unit 100 are controlled based on the image density information. The parameter here is a supply amount of toner in the developing device 14. FIG. 10A is a diagram showing changes in the color difference ΔE (95% tile value), where the vertical axis represents the color difference ΔE (95% tile value) and the horizontal axis represents the number of processed documents (sheets). FIG. 10B shows changes in the potential difference Vdev between the surface potential of the photosensitive drum 11 measured by the potential sensor 18 and the bias potential applied to the developing unit 14 in each of the image forming units 10Y, 10M, 10C, and 10K. The vertical axis represents potential difference Vdev, and the horizontal axis represents time (seconds). In addition, Y, M, C, and K are written so as to correspond to the image forming units 10Y, 10M, 10C, and 10K, respectively.
As shown in FIG. 10A, the image density is extremely low at 1.5% from 0 to 4000 sheets, and the image density is as high as 40% when 4000 sheets are exceeded.
Further, as shown in FIG. 10B, image formation (processing) is interrupted when 2300 seconds have elapsed, and then restarted.

In this embodiment, even when the image density is low from 0 to 4000, the amount of toner supplied is increased from the amount necessary for image formation. As a result, when the toner supply amount described later is not larger than the amount necessary for image formation (see FIG. 11 described later), the 1500th sheet timing T10 and the 3000th sheet timing when image quality adjustment (toner refresh) is performed. It is not necessary to perform image quality adjustment (toner refresh) at T11 (for this reason, it is expressed as image quality adjustment (toner refresh) scheduled timing T10 and image quality adjustment (toner refresh) scheduled timing T11). Therefore, as shown in FIG. 10A, even when the image density is low from 0 to 4000, the variation in the color difference ΔE (95% tile value) is small.
Further, although the image density is increased from 4000 sheets, the change of the color difference ΔE (95% tile value) at the boundary between the low image density and the high image density is 1.2, and the toner supply amount described later is changed to the image formation. It is small compared with the case where it is not increased more than the amount required for.

  Further, as shown in FIG. 10B, the potential difference Vdev increases with time, but its change is small. Even before and after the image quality adjustment (toner refresh) scheduled timing T10 in 1900 seconds, the fluctuation of the potential difference Vdev is small compared to the case where the amount of toner supply described later is not increased beyond the amount necessary for image formation.

  When resuming after the interruption, the potential difference Vdev is the same as before the interruption, and there is no change.

FIG. 11 is a diagram illustrating a case where the amount of toner supply is not increased beyond the amount necessary for image formation. FIG. 11A is a diagram showing a change in the color difference ΔE (95% tile value) as in FIG. 10A, where the vertical axis represents the color difference ΔE (95% tile value) and the horizontal axis represents the processing. This is the number of sheets. FIG. 11B shows a change in the potential difference Vdev between the surface potential of the photosensitive drum 11 and the bias potential applied to the developing unit 14 in each of the image forming units 10Y, 10M, 10C, and 10K, as in FIG. The vertical axis represents potential difference Vdev, and the horizontal axis represents time (seconds). In addition, Y, M, C, and K are written so as to correspond to the image forming units 10Y, 10M, 10C, and 10K, respectively.
As shown in FIG. 11A, as in FIG. 10A, the image density is extremely low at 1.5% from 0 to 4000 sheets, and the image density is as high as 40% when 4000 sheets are exceeded. ing.

Here, even when the image density is low from 0 to 4000, the toner supply amount is set to an amount necessary for image formation. Therefore, the image formation control unit 50 sets the image quality adjustment (toner refresh) timing T10 when the 1500th image is formed (processed) according to the accumulated image density, and the image quality when the 3000th image is formed (processed). Adjustment (toner refresh) timing T11 is provided. For this reason, as shown in FIG. 11A, the image quality adjustment (toner refresh) timing T10 and the image quality adjustment (toner refresh) timing T11 have large fluctuations such that the color difference ΔE (95% tile value) becomes 8 or more. Has occurred.
Furthermore, although the image density shifts from 4000 sheets to a high image density, there is a large variation in which the color difference ΔE (95% tile value) is 8 or more.

As shown in FIG. 11B, the potential difference Vdev increases with time, but the image quality adjustment (toner refresh) timing T10 (corresponding to 1900 seconds) and the image quality adjustment (toner refresh) timing T11 (corresponding to 3800 seconds). ), The toner is refreshed and descends.
The fluctuation of the potential difference Vdev between toner refreshes is larger than that in the case of controlling the parameters of the image forming unit 100 based on the image density information described with reference to FIG.

As described above with reference to FIGS. 10 and 11, the image formation control unit 50 is based on image density information obtained by pre-reading a document even when a low image density document is continuously flowed. However, by setting the toner supply amount to the developing device 14 high, it is possible to prevent the toner from being abnormally charged and to prevent toner refresh. Thus, by suppressing execution of image quality adjustment (toner refresh) during job execution, job processing time can be shortened, and continuity of image quality (color difference ΔE, etc.) in the job can be maintained.
Further, even when a document having a high image density is flowed after a document having an extremely low image density is continuously flowed, fluctuations in image quality (color difference ΔE) can be reduced.

Note that the threshold value Td indicates that the image formation control unit 50 performs toner refresh based on the accumulated image density value and the potential of the photosensitive drum 11 when continuously forming (processing) images with low image density. What is necessary is just to be able to suppress entering into the mode to perform.
Further, by setting the toner supply amount high, the image density increases. This can be dealt with by detecting and adjusting the potential difference Vdev between the surface potential of the photosensitive drum 11 and the bias potential applied to the developing device 14.
If the increase in toner charge amount cannot be suppressed even if the toner supply amount is set high, image quality adjustment (toner refresh) may be executed after the job is completed.

As described above, in the present embodiment, the image processing apparatus 40 acquires job information (information such as the number of documents, paper type information, and image density information) by prefetching a plurality of documents. The image formation control unit 50 receives these pieces of information and sets parameters for controlling the image formation unit 100. That is, feedforward control is performed. This cancels or avoids image quality adjustment (toner refresh, parameter change, etc.) that occurs during job execution, suppresses image quality fluctuations, and shortens the time required for the job.
On the other hand, when a plurality of documents are not prefetched, it is not possible to determine whether to stop or avoid image quality adjustment. In the case of not pre-reading a plurality of documents, in so-called feedback control, parameters for image formation (processing) of the next document can only be set according to the image quality of the formed image.

In this embodiment, the image processing apparatus 40 fetches job information (information such as the number of documents, paper identification information, and image density information) by pre-reading the document. Other information used to control the forming unit 100 may be extracted.
In this embodiment, the number of documents to be pre-read is 127. However, it may be set arbitrarily according to the performance of the image processing apparatus 40 and the image formation control unit 50.
Further, in the present embodiment, the image density is extracted from the raster image data of the original image data, but may be calculated from a preview image formed by thinning out the resolution of the original.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... PC, 3 ... Image reading apparatus, 10Y, 10M, 10C, 10K ... Image forming unit, 11 ... Photosensitive drum, 12 ... Charger, 13 ... Laser exposure device, 14 ... Developing device, DESCRIPTION OF SYMBOLS 15 ... Intermediate transfer belt, 18 ... Potential sensor, 20 ... Primary transfer part, 30 ... Secondary transfer part, 40 ... Image processing apparatus, 43 ... Image density sensor, 44 ... Image detection sensor, 50 ... Image formation control part, 60 ... Fixing unit, 100 ... Image forming unit, 401 ... Image data generating unit, 402 ... Color converting unit, 403 ... Image analyzing unit, 404 ... Job information generating unit, 501 ... Halftone processing unit, 502 ... Process control unit, 503 ... Color registration control unit, 504 ... Job information processing unit

Claims (6)

An image forming unit that develops the electrostatic latent image formed on the image carrier with a developer and transfers the image to a recording material to form an image;
Requirement information that defines requirements for image formation for a plurality of documents in one unit of work for collectively forming images, and image information that defines images for each document of the plurality of documents. Image formation for controlling the image forming unit by determining whether or not to change a condition for adjusting the image quality of the image formed in the image forming unit from a predetermined condition based on the requirement information An image forming apparatus comprising a control unit. The requirement information includes an image density that is a ratio of an area occupied by the developer to the recording material in each of the plurality of documents.
The condition for adjusting the image quality is a condition for supplying the developer,
When the image formation control unit determines that a document having an image density equal to or lower than a predetermined image density is to be continued more than a predetermined number based on the image density in the requirement information, the image density The image forming apparatus according to claim 1, wherein the image forming apparatus is changed to a condition different from a condition for supplying a predetermined developer corresponding to. The requirement information includes a separation between the work divisions or divisions having different requirements for image formation in the plurality of documents.
The condition for adjusting the image quality is a timing scheduled for adjusting the image quality,
When the image formation control unit determines that the number of documents to be processed with the image quality adjusted at the timing based on the separation in the requirement information is equal to or less than a predetermined number, the image formation control unit determines the image quality at the timing. The image forming apparatus according to claim 1, wherein the image forming apparatus is not adjusted. A requirement information generation unit that reads a plurality of documents in one unit of work for performing image formation collectively, extracts requirement information that defines requirements for image formation on the plurality of documents, and outputs the requirements information;
An image processing apparatus comprising: an image information generation unit that extracts and outputs image information that defines an image for each of the plurality of documents.   5. The image according to claim 4, wherein the requirement information includes an image density that is a ratio of an area occupied by a developer to a recording material on which an image is formed in each of the plurality of documents. Processing equipment.   The image processing apparatus according to claim 4, wherein the requirement information includes a division of the work or a division having different image formation requirements for the plurality of documents.

Images