JP2019159035A - Image forming apparatus - Google Patents

Abstract

To solve the problem in which: conventionally, even through a change in magnification in the conveyance direction of an image formed on a sheet is different for every job, adjustment of the magnification in the conveyance direction depending on a job cannot be performed, and the size of the image formed on the sheet may be different from an intended one.SOLUTION: A coverage acquisition unit included in an image forming apparatus acquires the coverage of an image transferred to a sheet by a transfer unit. A control unit determines an adjustment value of the magnification in a conveyance direction used for adjusting the magnification in the conveyance direction of an image changing in the conveyance direction on the basis of the coverage, and adjusts the magnification in the conveyance direction of an image formed by an image forming unit.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus.

  In general, a fixing device provided in an electrophotographic image forming apparatus fixes an image on a sheet by applying heat and pressure to a sheet on which an image of toner is formed. In this fixing device, the sheet on which the image is formed is fixed by being sandwiched between a pair of fixing rollers including a heating roller and a pressure roller.

  When the sheet is heated and pressurized by the fixing device and the image transferred on the surface of the sheet is fixed, the sheet temporarily expands. Then, after the image is transferred to the back surface of the expanded paper, the image is fixed on the paper, and then the paper is discharged, the paper cools with time. When the paper cools, the paper shrinks, and the size of the image fixed at the same position on the front and back surfaces changes. In order to prevent a change in an image fixed on a sheet, techniques disclosed in Patent Documents 1 and 2 below have been provided.

  Patent Document 1 discloses a technique for predicting the elongation of the intermediate transfer belt according to the paper type, adjusting the belt tension roller pressure, and adjusting the vertical magnification of the image formed on the paper.

  Patent Document 2 discloses a technique for controlling the vertical separation of the image by controlling the pressure separation timing of the front and rear rollers so as not to slip even at a transfer portion having a small conveying force.

JP 2007-3714 A JP 2013-151353 A

  Incidentally, the magnification of an image transferred onto a sheet by the transfer unit may change in the conveyance direction in which the sheet is conveyed by the conveyance unit in the image forming apparatus. Such a magnification in the conveyance direction of the image is referred to as “conveyance direction magnification”. The magnification in the conveyance direction varies depending on the coverage of the image formed on the paper. However, in the conventional technique, the influence of coverage is not considered when adjusting the magnification in the conveyance direction.

  For example, in the control of the elongation of the intermediate transfer belt disclosed in Patent Document 1 and the swing control of the registration roller pair disclosed in Patent Document 2, which are performed for the purpose of dealing with only a specific condition, the influence of coverage is affected. The magnification in the conveyance direction of the image that changes due to the above could not be adjusted sufficiently.

  SUMMARY An advantage of some aspects of the invention is that it adjusts a change in magnification in a conveyance direction of an image formed on a sheet.

  In order to achieve the above-described object, an image forming apparatus reflecting one aspect of the present invention includes a conveyance unit that conveys a sheet, an image formation unit that forms an image, and a conveyance unit that conveys the sheet. A transfer unit that is provided downstream of the image forming unit and transfers the image formed by the image forming unit to a sheet; a fixing unit that is provided downstream of the transfer unit and fixes the image transferred to the sheet; A coverage acquisition unit that acquires the coverage of the image transferred to the paper by the unit, and, based on the coverage, determines an adjustment value of the conveyance direction magnification used to adjust the conveyance direction magnification of the image that changes in the conveyance direction; A control unit that adjusts a magnification in a conveyance direction of an image formed by the image forming unit.

According to the present invention, since the change in the magnification in the conveyance direction of the image formed on the sheet is suppressed based on the coverage of the job executed this time, the print quality is improved.
Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

1 is a schematic configuration diagram illustrating a configuration example of an image forming apparatus according to a first embodiment of the present invention. 1 is a hardware configuration diagram illustrating a configuration example of a main part of an image forming apparatus according to a first embodiment of the present invention. It is a block diagram which shows the example of an internal structure of the control part which concerns on the 1st Embodiment of this invention. 6 is a graph showing a conveyance direction magnification ratio of a conveyance direction magnification of a sheet on which a blue solid image is fixed with respect to a conveyance direction magnification of a sheet on which only a line drawing image is fixed according to the first embodiment of the present invention. It is a graph which shows the relationship between the coverage which concerns on the 1st Embodiment of this invention, and the adjustment value of a conveyance direction magnification. It is explanatory drawing which shows the structural example of two types of tables contained in the corresponding | compatible table which concerns on the 1st Embodiment of this invention. 4 is a flowchart illustrating an example of processing for adjusting a magnification in a conveyance direction for each page performed in the image forming apparatus according to the first exemplary embodiment of the present invention. It is a block diagram which shows the schematic structural example of the image forming system which concerns on the 2nd Embodiment of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same function or configuration are denoted by the same reference numerals, and redundant description is omitted.

[First Embodiment]
<Example of Hardware Configuration of Image Forming Apparatus>
FIG. 1 is a schematic configuration diagram showing a configuration example of an image forming apparatus 1 according to the first embodiment of the present invention. In this block diagram, only elements considered necessary for explaining the present invention or related elements are described, and the image forming apparatus is not limited to this example.

  An example of the image forming apparatus 1 is an electrophotographic image forming apparatus such as a copying machine. The image forming apparatus 1 shown in FIG. 1 is also referred to as a so-called tandem color image forming apparatus, and forms a full-color image by arranging a plurality of photoconductors facing one intermediate transfer belt in the vertical direction. Is possible.

The image forming apparatus 1 includes an automatic document feeder 20 (ADF: Auto Document Feeder), an image forming unit 40, a paper conveying unit 50, and a fixing unit 60.
The automatic document feeder 20 scans and exposes an image of a document with an optical system of a scanning exposure device, and reads the reflected light with a line image sensor to obtain an image signal.

  The image forming unit 40 forms an image transferred onto the paper S by the secondary transfer unit 48. The image forming unit 40 includes an image forming unit 40Y that forms a yellow (Y) image, an image forming unit 40M that forms a magenta (M) image, an image forming unit 40C that forms a cyan (C) image, and a black ( The image forming unit 40K for forming the image of K) is provided.

  The image forming unit 40Y includes a photosensitive drum Y, a charging unit 42Y disposed around the photosensitive drum Y, an optical writing unit 43Y having a laser diode 41Y, a developing device 44Y, and a drum cleaner 45Y. Similarly, the image forming units 40M, 41C, and 41K are optical writing units that include the photosensitive drums M, C, and K, and charging units 42M, 42C, and 42K disposed around the photosensitive drums M, C, and K, and laser diodes 41M, 41C, and 41K. 43M, 43C, 43K, developing devices 44M, 44C, 44K and drum cleaners 45M, 45C, 45K.

  The surface of the photosensitive drum Y is uniformly charged by the charging unit 42Y, and a latent image is formed on the photosensitive drum Y by scanning exposure from the laser diode 41Y of the optical writing unit 43Y. Further, the developing device 44Y develops the latent image on the photosensitive drum Y by developing with toner. As a result, an image of a predetermined color corresponding to yellow is formed on the photosensitive drum Y.

  Similarly, the surface of the photosensitive drum M is uniformly charged by the charging unit 42M, and a latent image is formed on the photosensitive drum M by scanning exposure from the laser diode 41M of the optical writing unit 43M. The Further, the developing device 44M develops the latent image on the photosensitive drum M by developing with toner. As a result, an image of a predetermined color corresponding to magenta is formed on the photosensitive drum M.

  The surface of the photosensitive drum C is uniformly charged by the charging unit 42C, and a latent image is formed on the photosensitive drum C by scanning exposure from the laser diode 41C of the optical writing unit 43C. Further, the developing device 44C develops the latent image on the photosensitive drum C by developing with toner. As a result, an image of a predetermined color corresponding to cyan is formed on the photosensitive drum C.

  The surface of the photosensitive drum K is uniformly charged by the charging unit 42K, and a latent image is formed on the photosensitive drum K by scanning exposure from the laser diode 41K of the optical writing unit 43K. Further, the developing device 44K develops the latent image on the photosensitive drum K by developing with toner. As a result, an image of a predetermined color corresponding to black is formed on the photosensitive drum K.

  Images formed on the photoconductive drums Y, M, C, and K are sequentially transferred to predetermined positions on the intermediate transfer belt 46 that is a belt-shaped intermediate transfer body by primary transfer rollers 47Y, 47M, 47C, and 47K. Transcribed.

  The secondary transfer section 48 is provided downstream of the image forming section 40 along the transport direction in which the paper transport section 50 transports the paper S, and transfers the image formed by the image forming section 40 onto the paper S. At this time, the image composed of each color transferred onto the intermediate transfer belt 46 is transferred by the secondary transfer unit 48 to the paper S conveyed by the paper conveyance unit 50 at a predetermined timing.

  The paper transport unit 50 includes a plurality of paper feeding devices 51 in which the paper S is stored, a paper feeding unit 51 a that feeds and feeds the paper S stored in the paper feeding device 51, and a transport path of the paper S. And provided with various rollers. The paper transport unit 50 is fed from the paper feeding device 51 and branches from the main transport path 53 on the downstream side of the main transport path 53 and the fixing unit 60 where the fed paper S is transported. Are provided with a reverse conveyance path 54 for reversing the paper and a paper discharge tray 55 for discharging the paper S.

  The paper transport unit 50 includes a switching gate 53a provided at a branch point between the reverse transport path 54 and the main transport path 53, and transports the paper S in a certain transport direction. In the image forming apparatus 1, the sheet S is conveyed along the main conveyance path 53, the skew of the sheet S is corrected by the registration roller pair 57, and passes through the secondary transfer unit 48 and the fixing unit 60, so The image transferred to the upper surface (front surface) is fixed on the paper S. When images are formed on both sides of the sheet S, the sheet S on which the image is formed on the side facing upward is conveyed from the main conveyance path 53 to the reverse conveyance path 54. Then, the sheet S is reversed in the sheet reversal conveyance path 56 provided in the reversal conveyance path 54, so that the image forming surface (front surface) of the sheet S faces downward. Thereafter, the sheet S is transported to the main transport path 53. As a result, the paper S is turned upside down, and an image is formed on the other image forming surface (back surface) facing the upper side of the paper S.

  The fixing unit 60 is provided downstream of the secondary transfer unit 48 and fixes the image transferred by the secondary transfer unit 48 onto the paper S. For this reason, the fixing unit 60 conveys the sheet S by the pair of the upper pressure roller 61 and the lower pressure roller 62 that are in pressure contact with each other, and performs a fixing process for fixing the image to the sheet S on which the image is transferred. Do. Both the upper pressure roller 61 and the lower pressure roller 62 are used as fixing members. A heater H is provided inside the heating roller 64. The heater H heats the heating roller 64 to heat the fixing belt 63 so that heat is transmitted to the sheet S passing through the fixing nip N between the fixing belt 63 and the lower pressure roller 62. The heated fixing belt 63 rotates to transmit heat to the upper pressure roller 61 and to transfer heat to the sheet S passing through the fixing nip N. When the sheet S is heated, the image on the sheet S is melted and the image is fixed on the sheet S. Therefore, the fixing belt 63 is also used as a fixing member that fixes the image on the paper S. In this way, the image formed by the image forming unit 40 is transferred to the paper S by the secondary transfer unit 48 and fixed by the fixing unit 60, thereby completing the printing.

  The reading unit 58 is disposed downstream of the secondary transfer unit 48 and upstream of the fixing unit 60, that is, between the secondary transfer unit 48 and the fixing unit 60. The reading unit 58 is transferred from the secondary transfer unit 48 to the upper surface of the sheet S conveyed along the main conveyance path 53 from the secondary transfer unit 48 toward the fixing unit 60 and is expressed by the fixing unit 60 as indicated by broken line arrows in the drawing. It is possible to read the image before being fixed and calculate the coverage of the image transferred to the paper S. Then, the reading unit 58 outputs the calculated coverage to the control unit 11 (see FIG. 3 described later).

<Configuration of main part of image forming apparatus>
FIG. 2 is a hardware configuration diagram illustrating a configuration example of a main part of the image forming apparatus 1.
In addition to the automatic document feeder 20, the operation display unit 21, the image forming unit 40, the secondary transfer unit 48, the reading unit 58, and the fixing unit 60, the image forming apparatus 1 includes the control unit 11, the HDD 12, and the communication I. / F (Interface) 13 is provided. Each unit in the image forming apparatus 1 is connected via a bus.

  The control unit 11 includes a CPU 11a, a ROM 11b, and a RAM 11c. The control unit 11 is used as an example of a computer that controls the operation of each unit in the image forming apparatus 1. The control unit 11 according to the present embodiment uses the conveyance direction magnification used to adjust the conveyance direction magnification of the image that changes in the conveyance direction based on the coverage of the image transferred to the paper S by the secondary transfer unit 48. Determine the adjustment value. Then, the control unit 11 outputs the adjustment value to the image forming unit 40 to adjust the magnification in the conveyance direction of the image formed by the image forming unit 40.

The CPU (Central Processing Unit) 11a controls the image forming process (printing operation) of the image forming unit 40 based on, for example, the user's print instruction given through the operation display unit 21 and the contents set in the job.
A ROM (Read Only Memory) 11b is used as an example of a nonvolatile memory, and stores programs, data, and the like necessary for the operation of the CPU 11a.
A RAM (Random Access Memory) 11c is used as an example of a volatile memory, and temporarily stores information (data) necessary for each process performed by the CPU 11a.

  The HDD 12 stores a program for the CPU 11a to control each unit, a program such as an OS and a controller, and data. Some of the programs and data stored in the HDD 12 are also stored in the ROM 11b. The HDD 12 is used as an example of a computer-readable non-transitory storage device that stores a program executed by the CPU 11a. The computer-readable non-transitory storage device storing the program executed by the image forming apparatus 1 is not limited to the HDD, and for example, an SSD (Solid State Drive), a CD-ROM, a DVD-ROM. Etc.

  The communication I / F 13 is an example of a communication unit that includes, for example, a NIC (Network Interface Card), a modem, and the like, establishes a connection with each device such as a print controller (not shown), and transmits and receives various data. .

FIG. 3 is a block diagram illustrating an internal configuration example of the control unit 11.
The control unit 11 includes a job input unit 31, a coverage acquisition unit 32, an adjustment value determination unit 33, and a correspondence table 34. The job input unit 31, the coverage acquisition unit 32, and the adjustment value determination unit 33 are examples of functions realized by the CPU 11a illustrated in FIG. 2 executing a program. The correspondence table 34 is data that is stored in the RAM 11c and is appropriately read out by the CPU 11a, for example. The correspondence table 34 may be stored in the HDD 12.

  The control unit 11 adjusts the magnification in the conveyance direction of the image formed by the image forming unit 40 based on the adjustment value acquired from the correspondence table 34. For example, when a job image having a length of 100 mm in the conveyance direction is formed on the back surface of the paper S as it is, the length in the conveyance direction of the image formed on the paper S is changed to 99 mm when the paper S is cooled. In this case, 100/99 is obtained as the adjustment value of the conveyance direction magnification. And 100/99 calculated | required as an adjustment value from the operation display part 21 is input. Accordingly, the control unit 11 can give an instruction to form an image to the image forming unit 40 at a magnification in the conveyance direction that can correct the length in the conveyance direction of the image formed on the paper S to, for example, 101 mm. Become. Then, after the image is formed on the paper S, when the paper S discharged from the paper discharge tray 55 is cooled, the paper S contracts, so that the length of the image formed on the paper S in the transport direction is 100 mm. Become.

  For example, the magnification in the conveyance direction of the image formed on the photosensitive drum Y shown in FIG. 1 by the image forming unit 40 is adjusted according to the adjustment value of the magnification in the conveyance direction input from the operation display unit 21. Then, an image is formed on the photoconductive drums M, C, and K with the conveyance direction magnification changed according to the adjustment value as with the photoconductive drum Y. Thereafter, the image with the conveyance direction magnification adjusted is transferred onto the paper S by the secondary transfer unit 48. For this reason, the image transferred to the paper S is an image in which the conveyance direction magnification is adjusted.

  A job is input to the job input unit 31 from a client terminal (not shown) connected to the image forming apparatus 1 or a print controller. The job input unit 31 also inputs a job executed in the past read from the HDD 12. The job input unit 31 acquires a job image included in the job based on the job information of the input job. The job information includes information such as the number of printed sheets S.

  The coverage acquisition unit 32 acquires the coverage of the image transferred to the paper S by the secondary transfer unit 48. Here, there are several methods for the coverage acquisition unit 32 to acquire the coverage. The first method is a method in which the coverage acquisition unit 32 acquires the coverage for each job or each page based on the job image included in the job input to the job input unit 31 prior to the start of the printing process. In the present embodiment, a process in which the coverage acquisition unit 32 acquires coverage by the first method is adopted. The second method is a method in which the coverage acquisition unit 32 acquires the coverage calculated by the reading unit 58 reading the paper S during the printing process. In the second method, the coverage calculated based on the image actually transferred to the paper S is acquired. For this reason, the coverage acquisition unit 32 can accurately acquire a change in coverage even when an unintended operation occurs in the printing process.

  The adjustment value determination unit 33 adjusts the magnification in the conveyance direction based on the coverage for each job or page calculated from the job image of the job input to the job input unit 31 by the coverage acquisition unit 32 at the first execution timing of the job. Determine the value. The adjustment value determination unit 33 can also determine the adjustment value of the conveyance direction magnification based on the coverage transferred to the paper S by the secondary transfer unit 48 and acquired by the coverage acquisition unit 32. The adjustment value of the conveyance direction magnification determined by the adjustment value determination unit 33 based on the coverage is stored in the correspondence table 34.

  Then, the adjustment value determination unit 33 outputs the determined adjustment value of the conveyance direction magnification to the image forming unit 40. In accordance with the adjustment value input from the adjustment value determination unit 33, the image forming unit 40 forms an image with the conveyance direction magnification adjusted in subsequent job execution. Further, the adjustment value determination unit 33 can store the relationship between the coverage when the adjustment value is output to the image forming unit 40 and the adjustment value of the conveyance direction magnification in the correspondence table 34. Thereby, the adjustment value determination unit 33 can determine the adjustment value of the conveyance direction magnification based on the coverage of the job image formed on the paper S as the job is executed.

  Further, the adjustment value determination unit 33 uses the adjustment value of the conveyance direction magnification stored in the correspondence table 34 when the same job as the job executed in the past is executed. As a result, the magnification in the conveyance direction of the image formed by the image forming unit 40 can be accurately adjusted even when jobs are not continuously input to the job input unit 31.

  The correspondence table 34 is a table that holds the correspondence between the coverage and the adjustment value of the conveyance direction magnification. As shown in FIG. 6 to be described later, the correspondence table 34 is a correspondence relationship between a coverage adjustment value table 34a in which a correspondence relationship between coverage and an adjustment value of a conveyance direction magnification is defined in advance, and an adjustment value of a job and a conveyance direction magnification. Is provided with a job adjustment value table 34b.

  The adjustment value determination unit 33 refers to the coverage adjustment value table 34a, so that the conveyance direction magnification corresponding to the coverage for each page calculated by the coverage acquisition unit 32 based on the job image of the job input to the job input unit 31. Can be obtained. The relationship between the coverage of the paper S stored in the correspondence table 34 and the adjustment value of the conveyance direction magnification will be described in detail later with reference to FIG.

  On the other hand, the image forming unit 40 forms an image based on the job image output from the control unit 11, and the secondary transfer unit 48 transfers the image onto the paper S. Thereafter, the reading unit 58 reads the image transferred on the paper S, and the fixing unit 60 fixes the image on the paper S. In this case, the coverage value of the sheet S acquired from the reading unit 58 by the coverage acquisition unit 32 is input by the adjustment value determination unit 33. For this reason, the adjustment value of the conveyance direction magnification determined by the adjustment value determination unit 33 is stored in the correspondence table 34 for each page or each job.

<Explanation of magnification in transport direction>
As described above, the fixing unit 60 heats and pressurizes the sheet S on which the image is transferred to the front surface, whereby the sheet S expands, and the image is transferred to the back surface of the sheet S, and the fixing unit 60 heats and pressurizes. When the finished paper S is cooled, the magnification in the transport direction of the image printed on the paper S is reduced. In addition to heating and pressurization by the fixing unit 60, coverage may be cited as a factor that changes the magnification in the conveyance direction.

  The coverage represents, for example, the usage rate (%) of toner used for the paper S per sheet. For example, when the entire paper is solidly painted in black, the coverage of black toner is 100%. Further, if black is not used for the entire paper but is blank, the black toner coverage is 0%. Further, when the entire paper is solidly painted in blue, the coverage of cyan toner is 100% and the coverage of magenta toner is 100%, so that the total coverage is 200%. When the coverage is large, the sheet S is likely to slip at a position where the secondary transfer unit 48 transfers the image to the sheet S. For this reason, the length in the conveyance direction of the image transferred onto the paper S is slightly shorter than the length in the conveyance direction of the image formed by the image forming unit 40, and the magnification in the conveyance direction of the image formed on the paper S is increased. Get smaller.

<Example of change in magnification in conveyance direction according to paper type>
Here, with reference to FIG. 4, an example in which the magnification in the conveyance direction changes due to different paper types will be described.
FIG. 4 is a graph showing the conveyance direction magnification ratio of the conveyance direction magnification of the paper S on which the blue solid image is fixed with respect to the conveyance direction magnification of the paper S on which only the line drawing image is fixed.

In this graph, the magnification ratio in the transport direction on the front surface and the back surface of the coated paper and the high-quality paper (1) and (2), which are types of the paper S, is represented. The high quality paper (1) is a paper having a higher weight per quality paper than the high quality paper (2). For example, the high quality paper (1) is 105 g / m ² and the high quality paper (2) is 52.3 g / m. ² . If the conveyance direction magnification of the sheet S on which only the line image is fixed and the conveyance direction magnification of the sheet S on which the blue solid image is fixed are the same, the conveyance direction magnification ratio is 100.0%. If the conveyance direction magnification of the sheet S on which only the line image is fixed is larger than the conveyance direction magnification of the sheet S on which the blue solid image is fixed, the conveyance direction magnification ratio is as small as 99.9% or 99.8%. Become. On the other hand, if the conveyance direction magnification of the sheet S on which the blue solid image is fixed is larger than the conveyance direction magnification of the sheet S on which only the line image is fixed, the magnification ratio in the conveyance direction is 100.1% or 100.2%. Become bigger. The conveyance direction magnification ratio is allowed to vary within a range of 99.5% or more and 100.5% or less.

  For example, on the surface of the coated paper, the conveyance direction magnification of the sheet S on which only the line drawing image is fixed and the conveyance direction magnification of the sheet S on which the blue solid image is fixed are obtained. Then, the magnification ratio in the conveyance direction is obtained based on the magnification in the conveyance direction on the surface of the coated paper. Since the coated paper is coated with a coating for improving smoothness on both sides, even if the fixing unit 60 heats and pressurizes the coated paper, the coated paper hardly changes in expansion. For this reason, the conveyance direction magnification ratio on the surface of the coated paper is small. Also, the conveyance direction magnification ratio on the back surface of the coated paper is the same value as the conveyance direction magnification ratio on the front surface of the coated paper.

  Here, when the conveyance direction magnification ratio of each type of the paper S is compared, for example, the conveyance direction magnification ratio of the front surface and the back surface of the fine paper (1) is both higher than the conveyance direction magnification ratio of the front surface and the back surface of the coated paper. growing. Moreover, the conveyance direction magnification ratio on the surface of the fine paper (2) is substantially the same as the conveyance direction magnification ratio on the surface of the coated paper. However, the magnification ratio in the conveyance direction on the back surface of the high quality paper (2) is further larger than the magnification ratio in the conveyance direction on the back surface of the coated paper and the high quality paper (1). That is, as the paper S becomes lighter, the conveyance direction magnification ratio increases.

  As described above, the magnification ratio in the transport direction on the front surface and the back surface differs depending on the type of the paper S. Moreover, the conveyance direction magnification ratio of the back surface tends to be larger than the conveyance direction magnification ratio of the front surface. For this reason, when the image is transferred to the back surface of the paper S at the same magnification as the image transferred to the front surface of the paper S and the image is fixed, the size of the image on the front surface and the back surface of the paper S after the paper S cools down. Will be different. Therefore, the image forming apparatus 1 can adjust the magnification in the conveyance direction of images formed on the front surface and the back surface of the paper S based on the adjustment value of the conveyance direction magnification acquired based on the coverage.

<Relationship between coverage and adjustment value of magnification in conveyance direction>
FIG. 5 is a graph showing the relationship between the coverage and the adjustment value of the conveyance direction magnification. In this graph, the horizontal axis indicates the coverage for each job, and the vertical axis indicates the adjustment value of the conveyance direction magnification input according to the coverage.

  The coverage for each job shown in FIG. 5 is an average coverage that represents the average value of the coverage calculated for each job by the adjustment value determination unit 33. The average coverage is a value calculated by the adjustment value determination unit 33 for all job images included in the job based on the coverage acquired by the coverage acquisition unit 32. For example, if the coverage of the job image of the first page included in one job is 80% and the coverage of the job image of the second page is 10%, the average coverage is calculated as (80 + 10) / 2 = 45%. The

  As shown in FIG. 5, the plot in the figure indicates that the adjustment value of the conveyance direction magnification increases as the coverage for each job increases. For this reason, there is a certain degree of correlation between the coverage of the sheet S and the adjustment value of the conveyance direction magnification. Therefore, a linear line 71 of a linear expression obtained by linearly approximating the relationship between the coverage and the adjustment value of the magnification in the conveyance direction by, for example, the least square method can be drawn in the graph. The relationship between the average coverage and the adjustment value of the conveyance direction magnification may be approximated by a curve such as a quadratic expression.

  Then, the adjustment value determination unit 33 can determine the adjustment value of the conveyance direction magnification according to the job by a linear line 71 of a linear expression that linearly approximates the relationship between the average coverage and the adjustment value of the conveyance direction magnification. That is, the adjustment value determination unit 33 determines the adjustment value of the conveyance direction magnification corresponding to the coverage of the paper S calculated by the reading unit 58 from the coverage adjustment value table 34a shown in FIG. Instructs the adjustment value of the magnification in the conveyance direction. Thereby, the adjustment value determination part 33 can adjust the conveyance direction magnification of the image which the image formation part 40 forms based on the average value of coverage.

  The average coverage may be a value calculated on the basis of a passing result such as the number of pages of the paper S printed by the image forming apparatus 1. Then, the adjustment value determination unit 33 may calculate the average coverage by, for example, the time average for each week or the average number of sheets for every 10,000 sheets, or may calculate the average coverage by the average for each job. Thereby, the adjustment value determination unit 33 determines the adjustment value of the conveyance direction magnification corresponding to the average coverage of the paper S read from the coverage adjustment value table 34a, and outputs the adjustment value of the conveyance direction magnification to the image forming unit 40. be able to.

<Configuration example of correspondence table>
FIG. 6 is an explanatory diagram showing a configuration example of two types of tables included in the correspondence table 34. The correspondence table 34 includes a coverage adjustment value table 34a and a job adjustment value table 34b.

The coverage adjustment value table 34a has a coverage field and a conveyance direction magnification adjustment value field.
The coverage field stores the average coverage value shown in FIG.
The conveyance direction magnification adjustment value field stores the conveyance direction magnification adjustment value for the average coverage shown in FIG.

  In this way, data indicating the correlation between the average coverage described in FIG. 5 and the adjustment value of the conveyance direction magnification is stored in the coverage adjustment value table 34a. Since the adjustment value determination unit 33 creates the coverage adjustment value table 34a based on the graph shown in FIG. 5, the contents of the graph of FIG. 5 and the contents of the coverage adjustment value table 34a are substantially the same. Thereby, the adjustment value determination unit 33 determines the adjustment value of the conveyance direction magnification corresponding to the average coverage of the paper S read from the coverage adjustment value table 34a, and outputs the adjustment value of the conveyance direction magnification to the image forming unit 40. be able to.

The job adjustment value table 34b has a job ID field and a conveyance direction magnification adjustment value field.
The job ID field stores a job ID that uniquely identifies the job. If a job can be uniquely specified, a job name or the like may be stored instead of the job ID.
The conveyance direction magnification adjustment value field stores the conveyance direction magnification adjustment value determined by the adjustment value determination unit 33 when the job specified by the job ID has been executed in the past.

  As described above, the job ID of the job executed in the past and the adjustment value of the conveyance direction magnification determined in the past are stored in the job adjustment value table 34b. For this reason, if the job ID of the job executed this time is the same as the job ID of the job executed in the past, the adjustment value determination unit 33 adjusts the conveyance direction magnification adjustment value determined in the job executed in the past. Can be acquired from the job adjustment value table 34b, and the magnification in the conveyance direction can be adjusted for the image forming unit 40 by using the same adjustment value as the job executed in the past.

<Description of Processing of Image Forming Apparatus>
Next, processing performed in the image forming apparatus 1 will be described with reference to FIG.
FIG. 7 is a flowchart illustrating an example of processing for adjusting the conveyance direction magnification for each page performed in the image forming apparatus 1.

  First, the job input unit 31 of the image forming apparatus 1 stands by until a job is input from a client terminal (not shown) or a print controller (S1). When a job is input, the job input unit 31 stores the job in, for example, the HDD 12 (S2). When the job is executed, the following processing is performed based on the job stored in the HDD 12. If a job executed in the past stored in the HDD 12 in step S1 is input to the job input unit 31, the process of storing the job in the HDD 12 in step S2 is not performed, and the process proceeds to the next step S3.

  Next, the job input unit 31 determines whether or not the printing of the job stored in the HDD 12 is the first printing of the job (S3). If it is not the first printing (NO in S3), there is a record of printing using a job stored in the HDD 12 in the past. For this reason, the adjustment value determination unit 33 reads out and uses the adjustment value of the conveyance direction magnification used in the job executed in the past from the job adjustment value table 34b of the correspondence table 34 (S4). Transition to processing.

  In step S3, when the job input unit 31 determines that the job is printed for the first time (YES in S3), the adjustment value determination unit 33 acquires the coverage for each page from the job information ( S5). Then, the adjustment value determining unit 33 determines the adjustment value of the conveyance direction magnification corresponding to the acquired coverage from the coverage adjustment value table 34a of the correspondence table 34 (S6).

  Next, the adjustment value determining unit 33 determines whether or not to start job execution (S7). If the job execution is not started (NO in S7), the process returns to step S1 and continues waiting for job input by the job input unit 31.

  On the other hand, when the execution of the job is started (YES in S7), the paper transport unit 50 starts transporting the paper S (S8). At this time, the adjustment value determining unit 33 outputs the adjustment value determined from the job adjustment value table 34b to the image forming unit 40, so that the image position of the image formed by the image forming unit 40 is adjusted thereafter. The job is executed.

  Next, the image forming unit 40 adjusts the conveyance direction magnification of the image to be formed for each page according to the adjustment value of the conveyance direction magnification determined by the adjustment value determination unit 33 (S9). Next, the image formed by the image forming unit 40 is transferred by the secondary transfer unit 48 to the sheet S (S10), and the fixing unit 60 fixes the image transferred to the sheet S to the sheet S (S11). .

  Next, the control unit 11 determines whether or not the reverse side printing of the paper S is set based on the job information (S12). When the back side printing of the paper S is not set (NO in S12), the control unit 11 discharges the paper S on which the image is fixed only on the front surface to the paper discharge tray 55 (S17).

  On the other hand, when the reverse side printing of the paper S is set (YES in S12), the operator grasps the change in the conveyance direction magnification based on the images printed on both sides of the paper S, and adjusts the conveyance direction magnification. Will be entered. For this reason, the control unit 11 reverses the front and back of the paper S through the reverse conveyance path 54 (S13).

  Next, the adjustment value determination unit 33 determines the adjustment value of the conveyance direction magnification corresponding to the acquired coverage from the coverage adjustment value table 34a of the correspondence table 34 (S14). The image formed by the image forming unit 40 is transferred to the back surface of the paper S by the secondary transfer unit 48 (S15), and the fixing unit 60 fixes the image transferred to the paper S to the paper S (S16). Then, the control unit 11 discharges the paper S on which the image is fixed on the front and back surfaces to the paper discharge tray 55 (S17).

  Next, the control unit 11 determines whether there is a next sheet to be printed (S18). If there is a next sheet (YES in S18), the control unit 11 returns to step S8 to start conveyance of the next sheet and performs the subsequent processing. If there is no next sheet (NO in S18), printing is completed (S20). Then, the paper S on which the image is printed only on the front surface or the paper S on which the image is printed on the front and back surfaces is taken out from the paper discharge tray 55 by the operator.

  The adjustment value determined by the adjustment value determination unit 33 during execution of the current job is stored in the job adjustment value table 34b of the correspondence table 34 by the adjustment value determination unit 33 in association with the job ID.

  When the adjustment value of the conveyance direction magnification determined in the job executed in the past in step S4 is used, the adjustment value determination unit 33 reads from the job adjustment value table 34b based on the job ID of the job to be executed this time. The read adjustment value of the conveyance direction magnification is output to the image forming unit 40.

  In step S5, the coverage acquisition unit 32 performs processing for acquiring coverage from the job information. However, except for the processing in step S5, the first test printing is performed once, the image transferred to the front and back surfaces of the paper S is read by the reading unit 58, and the coverage calculated by the reading unit 58 is covered by the coverage acquisition unit 32. May get. Thereby, the adjustment value determining unit 33 can acquire the adjustment value of the conveyance direction magnification corresponding to the coverage from the correspondence table 34 and output the adjustment value to the image forming unit 40.

  In the image forming apparatus 1 according to the first embodiment described above, image formation is performed using the adjustment value of the conveyance direction magnification determined by the adjustment value determination unit 33 according to the coverage calculated for each job or page. The magnification in the conveyance direction of the image formed by the unit 40 is adjusted. For this reason, the image forming apparatus 1 can appropriately adjust the magnification in the conveyance direction of the image that changes according to the coverage.

  Further, the adjustment value determination unit 33 automatically determines the adjustment value of the conveyance direction magnification with reference to the correspondence table 34. When the same job as the job executed in the past is executed this time, the adjustment value determination unit 33 diverts the adjustment value of the conveyance direction magnification determined based on the job executed in the past to the job executed this time. be able to. For this reason, it is possible to save the trouble of inputting the adjustment value of the conveyance direction magnification every time the operator executes the job.

  Further, the coverage acquisition unit 32 adjusts the conveyance direction magnification based on the coverage calculated by the reading unit 58 not only from images printed on both sides of the paper S but also from images printed only on one side of the paper S. be able to.

  It may be possible to select whether or not to execute the process for determining the adjustment value of the conveyance direction magnification. For example, when the operation display unit 21 is turned on, a process for determining the adjustment value of the conveyance direction magnification is performed, but when the operation display unit 21 is turned off, the process is not performed. In this way, by inputting ON or OFF according to the type of job, it is possible to switch whether to execute the process for determining the adjustment value of the conveyance direction magnification.

Further, the adjustment value of the conveyance direction magnification may be input by manual input using the operation display unit 21 by an operator as in the past.
The adjustment value determination unit 33 may determine the adjustment value of the conveyance direction magnification based on the coverage of an arbitrary page selected from the job input to the job input unit 31.

[Second Embodiment]
Next, an image forming system according to a second embodiment of the present invention will be described.
FIG. 8 is a block diagram illustrating a schematic configuration example of the image forming system 10.

The image forming system 10 includes an image forming apparatus 1A and a reading device 2 (an example of a reading unit) connected to a subsequent stage of the image forming apparatus 1A.
The image forming apparatus 1 </ b> A has substantially the same configuration as the image forming apparatus 1 according to the first embodiment described above, except that the reading unit 58 and the paper discharge tray 55 are not provided. Therefore, the image forming apparatus 1 </ b> A outputs the paper S on which the image is fixed by the fixing unit 60 to the reading device 2.

  The reading device 2 simultaneously reads the images fixed on the paper S by the fixing unit 60 of the image forming apparatus 1A from above and below from the paper S, so that the coverage of the images printed on the front and back surfaces of the paper S is reached. Can be calculated for each surface. Then, the reading device 2 transmits the calculated coverage of the paper S to the coverage acquisition unit 32 and stores it in the coverage adjustment value table 34a of the correspondence table 34 provided in the image forming apparatus 1A.

  When the image forming apparatus 1A performs the first printing of a job, the following processing is performed instead of steps S5 and S6 from the flowchart according to the first embodiment shown in FIG. In other words, the reading device 2 reads the sheet S that the image forming apparatus 1A has test-printed the job and discharged to the reading device 2, and calculates the coverage. The coverage acquisition unit 32 of the image forming apparatus 1 </ b> A acquires the coverage calculated by the reading device 2. Thereby, the adjustment value determination unit 33 can determine the adjustment value of the magnification in the conveyance direction that is instructed to the image forming unit 40 when the job is executed. Thereafter, the processing after step S7 in the flowchart shown in FIG. 7 is performed.

  When a plurality of copies are set for a job, the image forming apparatus 1A performs test printing of the first copy, and the reading device 2 reads each page of the first copy, thereby calculating the coverage of each page. . Thereafter, the adjustment value determination unit 33 of the image forming apparatus 1A may determine the adjustment value of the magnification in the conveyance direction based on the coverage of each page calculated by the reading device 2 in the process of printing the second and subsequent copies. Good.

  In the image forming system 10 according to the second embodiment described above, the adjustment value determining unit 33 reads the coverage calculated by the reading device 2 for each page or job by reading the image printed on the paper S. The job adjustment value table 34b of the correspondence table 34 is stored. For this reason, even if the image forming apparatus 1A does not include the reading unit 58 shown in the first embodiment, coverage for each page or each job can be obtained simply by connecting the reading apparatus 2. After obtaining the coverage, as in the first embodiment, the adjustment value determining unit 33 refers to the correspondence table 34 to determine an adjustment value of an appropriate conveyance direction magnification, and the image forming unit 40 forms it. An instruction to adjust the magnification in the conveyance direction of the image can be issued. For this reason, the image forming unit 40 can form an image on the paper S with the conveyance direction magnification determined according to the coverage.

  Note that the reading unit 58 according to the first embodiment described above may be provided inside the image forming apparatus 1 and downstream of the fixing unit 60 in the conveyance direction. Accordingly, the adjustment value determination unit 33 can acquire the coverage calculated by the reading unit 58 without providing a reading device at the subsequent stage of the image forming apparatus 1. The image forming apparatus 1 can be configured not to include a reading device.

The present invention is not limited to the embodiment described above, and various other application examples and modifications can of course be taken without departing from the gist of the present invention described in the claims.
For example, the above-described embodiment is a detailed and specific description of the configuration of the apparatus and the system in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to one having all the described configurations. In addition, a part of the configuration of the embodiment described here can be replaced with the configuration of the other embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Is possible. Moreover, it is also possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.
Further, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 11 ... Control part, 21 ... Operation display part, 31 ... Job input part, 32 ... Coverage acquisition part, 33 ... Adjustment value determination part 33 ... Correspondence table, 40 ... Image forming part, 48 ... Secondary Transfer unit, 50... Paper transport unit, 51... Paper feeding device, 53... Main transport path, 58.

Claims (9)

A transport unit for transporting paper;
An image forming unit for forming an image;
A transfer unit that is provided downstream of the image forming unit along a transport direction in which the transport unit transports the paper, and that transfers the image formed by the image forming unit to the paper;
A fixing unit provided downstream of the transfer unit and fixing the image transferred to the paper;
Based on the coverage of the image transferred to the paper by the transfer unit, an adjustment value of the conveyance direction magnification used to adjust the conveyance direction magnification of the image that changes in the conveyance direction is determined, and the image formation A control unit that adjusts the magnification in the transport direction of the image formed by the unit. The image forming apparatus according to claim 1, wherein the control unit includes a coverage acquisition unit that acquires the coverage based on a job image included in a job. The said control part is provided between the said transfer part and the said fixing | fixed part, The coverage acquisition part which acquires the said coverage calculated by the reading part which reads the said image transcribe | transferred to the said sheet | seat is provided. Image forming apparatus. The image forming apparatus according to claim 1, wherein the control unit includes a coverage acquisition unit that is provided downstream of the fixing unit and acquires the coverage calculated by a reading unit that reads the image transferred to the sheet. The controller is
A correspondence table holding a correspondence relationship between the coverage and the adjustment value of the conveyance direction magnification;
The adjustment value determination part which determines the adjustment value of the said conveyance direction magnification based on the coverage of the said image transferred on the said sheet | seat with reference to the said correspondence table is provided. The image forming apparatus described. The adjustment value determination unit determines an adjustment value of the conveyance direction magnification for each page of the job based on the coverage acquired by the coverage acquisition unit, and the conveyance direction of the image formed by the image forming unit The image forming apparatus according to claim 5, wherein the magnification is adjusted. The image forming apparatus according to claim 6, wherein the adjustment value determination unit determines an adjustment value of the conveyance direction magnification based on the coverage of an arbitrary page selected from the job. The adjustment value determination unit calculates an average value of the coverage for each job based on the coverage acquired by the coverage acquisition unit, and the image forming unit forms the image based on the average value of coverage The image forming apparatus according to claim 5, wherein the magnification in the conveyance direction is adjusted. The image forming apparatus according to any one of claims 1 to 8, wherein execution of processing for determining an adjustment value of the conveyance direction magnification is selectable.

Images