JP2015199255A - Ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet printer capable of reducing convenience deterioration when changing an ink color.SOLUTION: An ink jet printer 1 includes: a printing part 33 which has ink jet heads 46A-46D, and discharges ink from the ink jet heads 46A-46D to print images; an image adjustment value storage part 71 which stores an image adjustment value corresponding to ink of a previously set color in each of the ink jet heads 46A-46D, and stores other additional image adjustment values; and a control part 10 which acquires an image adjustment value corresponding to ink after changing in the ink jet head 46 when ink discharged from the ink jet head is changed from ink of a previously set color to ink of another color, and adds the acquired image adjustment value to the image adjustment value storage part 71.

Description

  The present invention relates to an ink jet printing apparatus that performs printing by discharging ink from an ink jet head.

  2. Related Art There is known an inkjet printing apparatus capable of full color printing using cyan (C), magenta (M), yellow (Y), and black (K) inks (see, for example, Patent Document 1).

  However, even this inkjet printing apparatus may not be able to express the color desired by the user. Thus, the ink cartridge mounted on the apparatus may be replaced with another color ink cartridge to change the ink color ejected by the inkjet head. Thereby, it can change to the apparatus which can express the color which a user desires. For example, by replacing magenta ink with red (R) ink, red with high saturation can be expressed.

JP 2012-86489 A

  Each color ink used in the ink jet printing apparatus has different physical properties. For this reason, the ejection characteristics differ for each ink. Therefore, when the ink color is changed as described above, it is necessary to change the image adjustment value. For this purpose, it is necessary to perform image adjustment processing.

  In the image adjustment process, first, the inkjet printing apparatus prints a pattern image corresponding to an image adjustment item to be adjusted. Next, the printed pattern image is read by a scanner to generate image data. Then, the inkjet printing apparatus analyzes the image data and calculates an adjustment value in the image adjustment item to be adjusted. This is repeated for each image adjustment item. The image adjustment items include ink landing positions.

  Here, in the ink jet printing apparatus, image adjustment values corresponding to ink of a preset color in each ink jet head are stored. For example, in an apparatus having four inkjet heads and ejecting cyan, magenta, yellow, and black inks, image adjustment values corresponding to cyan, magenta, yellow, and black inks in each inkjet head are stored. . These image adjustment values are calculated by image adjustment processing at the time of manufacturing the ink jet printing apparatus.

  Conventionally, an ink jet printing apparatus has storage areas for image adjustment values only for the number of ink jet heads. For this reason, the image adjustment value calculated by the image adjustment process at the time of changing the ink color described above is overwritten and stored on the image adjustment value before the change in the ink-jet change target ink jet head. For example, in an inkjet head that ejects magenta ink, when the ejected ink is changed to red ink, the image adjustment value corresponding to red ink is overwritten and stored over the image adjustment value corresponding to magenta ink.

  By the way, the changed ink color may be restored. In this case, it is necessary to return the image adjustment value to that corresponding to the original color ink. However, as described above, the image adjustment value corresponding to the original color ink is replaced with the changed ink image adjustment value when the ink color is changed. Therefore, it is necessary to perform image adjustment processing in order to obtain an image adjustment value corresponding to the original color ink.

  As described above, in the ink jet printing apparatus, it is necessary to perform the image adjustment process when returning the ink color that has been changed once. Further, when the ink color is changed again after returning to the original color, it is also necessary to perform image adjustment processing. The image adjustment process requires a certain amount of time. During this time, the ink jet printing apparatus cannot be used for printing, resulting in a decrease in convenience for the user.

  The present invention has been made in view of the above, and an object of the present invention is to provide an ink jet printing apparatus that can reduce a decrease in convenience when an ink color is changed.

  In order to achieve the above object, a first feature of an ink jet printing apparatus according to the present invention includes at least one ink jet head, a printing unit that prints an image by ejecting ink from the ink jet head, and each ink jet. An image adjustment value storage unit that stores image adjustment values corresponding to ink of a preset color in the head and that can additionally store other image adjustment values, and ink ejected by the inkjet head are set in advance. When the changed color ink is changed to another color ink, the image adjustment value corresponding to the changed ink in the inkjet head is acquired, and the acquired image adjustment value is stored in the image adjustment value storage unit. And an image adjustment value acquisition unit to be added.

  A second feature of the inkjet printing apparatus according to the present invention is that the image adjustment value acquisition unit stores the image adjustment value corresponding to the changed ink in the inkjet head in which the color of the ink has been changed. The calculation is based on the correlation with the image adjustment value stored in the unit and corresponding to the color ink set in advance in the inkjet head.

  A third feature of the ink jet printing apparatus according to the present invention is that the ink jet head has at least one ink jet head, prints an image by discharging ink from the ink jet head, and the ink jet head in each ink jet head. An image adjustment value storage unit that stores an image adjustment value corresponding to the ink to be ejected, and an image adjustment value corresponding to the changed ink in the ink jet head when the ink color ejected by the ink jet head is changed Is calculated based on the correlation with the image adjustment value before the ink color change in the inkjet head stored in the image adjustment value storage unit, and the change of the ink color stored in the image adjustment value storage unit The previous image adjustment value is set to the calculated image adjustment value corresponding to the changed ink. In that and an image adjustment value acquisition unit to change.

  According to the first feature of the inkjet printing apparatus according to the present invention, the image adjustment value storage unit additionally adds an image adjustment value other than the image adjustment value corresponding to the preset color ink in each inkjet head. It can be saved. The image adjustment value acquisition unit obtains an image adjustment value corresponding to the changed ink in the inkjet head when the ink ejected by the inkjet head is changed from a preset color ink to another color ink. The acquired image adjustment value is added to the image adjustment value storage unit.

  Thus, even after the ink color change, the image adjustment value corresponding to the ink color before the change is stored in the image adjustment value storage unit. This eliminates the need for an image adjustment process for obtaining an image adjustment value when the ink color is changed back to the original ink. Further, even when the ink color is changed again after returning to the original ink, the image adjustment processing for acquiring the image adjustment value is not necessary. As a result, it is possible to reduce the situation in which the ink jet printing apparatus cannot be used because of the image adjustment process. Therefore, according to the first feature of the inkjet printing apparatus according to the present invention, it is possible to reduce the decrease in convenience when the ink color is changed.

  According to the second feature of the inkjet printing apparatus according to the present invention, the image adjustment value acquisition unit stores the image adjustment value corresponding to the changed ink in the inkjet head in which the color of the ink is changed, as an image adjustment value storage unit. Calculated on the basis of the correlation with the image adjustment value corresponding to the color ink set in advance in the inkjet head. As described above, the image adjustment value acquisition unit acquires the image adjustment value corresponding to the ink after the ink color change by calculation, so that the image adjustment process is unnecessary. Thus, even if the ink color is changed, there is no situation where the ink jet printing apparatus cannot be used because the image adjustment process is being performed. Therefore, according to the second feature of the inkjet printing apparatus according to the present invention, it is possible to further reduce the decrease in convenience when the ink color is changed.

  According to the third feature of the ink jet printing apparatus according to the present invention, the image adjustment value acquisition unit corresponds to the ink after the change in the ink jet head when the ink color discharged from the ink jet head is changed. The image adjustment value is calculated based on the correlation with the image adjustment value before changing the ink color in the inkjet head stored in the image adjustment value storage unit. As described above, the image adjustment value acquisition unit acquires the image adjustment value corresponding to the ink after the ink color change by calculation. Then, the image adjustment value acquisition unit replaces the image adjustment value before the ink color change stored in the image adjustment value storage unit with the image adjustment value corresponding to the ink after the ink color change.

  For this reason, even when there is no area for adding image adjustment values in the image adjustment value storage unit, image adjustment processing when changing the ink color is also included, including the case of changing the ink color to return the ink color that has been changed once. Is not necessary. Therefore, a situation in which the ink jet printing apparatus cannot be used because of the image adjustment process does not occur. Therefore, according to the third feature of the ink jet printing apparatus according to the present invention, even when the image adjustment value cannot be additionally stored, it is possible to reduce the decrease in convenience when the ink color is changed.

1 is a schematic configuration diagram of an inkjet printing apparatus according to a first embodiment. It is a control block diagram of the inkjet printing apparatus which concerns on 1st Embodiment. FIG. 6 is an enlarged view of the vicinity of a belt conveyance unit. It is explanatory drawing of arrangement | positioning of a head module. 6 is a flowchart for explaining an operation when changing an ink color in the ink jet printing apparatus according to the first embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, the same or equivalent parts and components are denoted by the same or equivalent reference numerals. However, it should be noted that the drawings are schematic and different from the actual ones. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  Further, the embodiment described below exemplifies an apparatus or the like for embodying the technical idea of the present invention, and the technical idea of the present invention includes the material, shape, structure, The layout is not specified as follows. The technical idea of the present invention can be variously modified within the scope of the claims.

(First embodiment)
FIG. 1 is a schematic configuration diagram of an inkjet printing apparatus according to a first embodiment of the present invention. FIG. 2 is a control block diagram of the ink jet printing apparatus shown in FIG. FIG. 3 is an enlarged view of the vicinity of the belt conveyance unit of the inkjet printing apparatus shown in FIG. FIG. 4 is an explanatory diagram of the arrangement of the head modules in the ink jet printing apparatus shown in FIG. In the following description, the direction orthogonal to the paper surface of FIG. 1 is the front-rear direction, and the front surface direction is the front. Also, the top, bottom, left, and right of the paper surface in FIG.

  In FIG. 1, a path indicated by a thick line is a transport path through which a sheet as a print medium is transported. Among the transport routes, a route indicated by a solid line is a normal route RC, a route indicated by a one-dot chain line is a reverse route RR, a route indicated by a broken line is a paper discharge route RD, and a route indicated by a two-dot chain line is a paper feed route RS. In the following description, upstream and downstream mean upstream and downstream in the transport path.

  As shown in FIGS. 1 and 2, the inkjet printing apparatus 1 according to the first embodiment includes a paper feeding unit 2, a transport printing unit 3, an upper surface transport unit 4, a paper discharge unit 5, and a reversing unit 6. The image reading unit 7, the operation panel unit 8, the storage unit 9, the control unit 10, and a housing 11 that stores or holds each unit.

  The paper feed unit 2 feeds the paper P. The paper feed unit 2 is arranged on the most upstream side of the transport path. The paper feed unit 2 includes an external paper feed base 21, an external paper feed roller 22, a plurality of internal paper feed stands 23, a plurality of internal paper feed rollers 24, a plurality of pairs of vertical transport rollers 25, and a registration roller 26. With.

  The external paper feed tray 21 is used for loading paper P used for printing. The external paper feed tray 21 is partly exposed outside the housing 11.

  The external paper feed roller 22 takes out the paper P one by one from the external paper feed tray 21 and conveys it toward the registration rollers 26 along the paper feed path RS. The external paper feed roller 22 is driven by a motor (not shown).

  The internal paper feed table 23 is used for loading paper P used for printing. The internal paper feed table 23 is disposed inside the housing 11.

  The internal paper feed roller 24 takes out the paper P one by one from the internal paper feed tray 23 and sends it out to the paper feed path RS. The internal paper feed roller 24 is driven by a motor (not shown).

  The vertical conveyance roller 25 conveys the paper P taken out from the internal paper feed table 23 toward the registration roller 26. The vertical conveyance roller 25 is disposed along the paper feed path RS. The vertical conveying roller 25 is driven by a motor (not shown).

  The registration roller 26 temporarily stops the paper P conveyed from the external paper feed tray 21, the internal paper feed tray 23, and the reversing unit 6, and then transports the paper P to the transport printing unit 3. The registration roller 26 is disposed on the normal route RC in the vicinity of the junction point between the sheet feeding route RS and the reverse route RR. The registration roller 26 is driven by a motor (not shown).

  The transport printing unit 3 prints an image on the paper P while transporting the paper P fed by the paper feeding unit 2. The conveyance printing unit 3 includes a belt conveyance unit 31, a paper sensor 32, and a printing unit 33.

  The belt conveyance unit 31 conveys the paper P conveyed from the registration roller 26. The belt conveyance unit 31 is disposed on the downstream side of the registration roller 26. The belt conveyance unit 31 includes a conveyance belt 36, a driving roller 37, driven rollers 38, 39, and 40, a belt motor 41, and an encoder 42.

  The transport belt 36 sucks and holds the paper P and transports it. The conveying belt 36 is an annular belt that is stretched around the driving roller 37 and the driven rollers 38 to 40. A number of through holes are formed in the transport belt 36. The conveyance belt 36 sucks and holds the paper P by the suction force generated in the through hole by driving a fan (not shown). The transport belt 36 rotates in the clockwise direction in FIG. 2 to transport the sucked and held paper P from left to right.

  The driving roller 37 supports the conveyor belt 36 together with the driven rollers 38 to 40 and rotates the conveyor belt 36.

  The driven rollers 38 to 40 support the conveying belt 36 together with the driving roller 37. The driven rollers 38 to 40 are driven by the driving roller 37 via the conveying belt 36. The driven roller 38 has the same height as the drive roller 37 and is disposed on the left side of the drive roller 37. The driven rollers 39 and 40 are spaced apart from each other in the left-right direction below the driving roller 37 and the driven roller 38 and are disposed at the same height.

  The belt motor 41 rotates the drive roller 37.

  The encoder 42 outputs a pulse signal for each predetermined rotation angle of the driven roller 38.

  The paper sensor 32 detects the paper P conveyed by the belt conveyance unit 31. The paper sensor 32 is disposed above the transport belt 36 and in the vicinity of the upstream side of an inkjet head 46A described later. As the paper sensor 32, an optical sensor having a light emitting element and a light receiving element can be applied.

  The printing unit 33 performs printing on the paper P using a plurality of colors of ink. The printing unit 33 includes inkjet heads 46A, 46B, 46C, and 46D, a head driving unit 47, ink cartridge mounting units 48A, 48B, 48C, and 48D, and ink cartridges 49K, 49C, 49M, and 49Y. Note that the alphabetic suffixes (A to D, K, C, M, and Y) are omitted from the inkjet heads 46A to 46D, the ink cartridge mounting portions 48A to 48D, and the ink cartridges 49K, 49C, 49M, and 49Y. May be written in the same way.

  The inkjet heads 46A, 46B, 46C, and 46D discharge ink supplied from ink cartridges 49K, 49C, 49M, and 49Y mounted on the ink cartridge mounting portions 48A, 48B, 48C, and 48D, respectively. That is, the inkjet heads 46A, 46B, 46C, and 46D eject black (K), cyan (C), magenta (M), and yellow (Y) inks, respectively. The inkjet heads 46 </ b> A to 46 </ b> D are arranged in parallel along the conveyance direction (left-right direction) of the paper P above the belt conveyance unit 31. As shown in FIG. 4, each of the inkjet heads 46 </ b> A to 46 </ b> D has six head modules 50.

  The head module 50 has a plurality of nozzles (not shown) arranged at a predetermined pitch along the main scanning direction (front-rear direction), and ejects ink from the nozzles. The head module 50 is supplied with ink from an ink cartridge 49 via an ink path (not shown). In each inkjet head 46, the six head modules 50 are staggered along the front-rear direction (main scanning direction). That is, the six head modules 50 are arranged along the front-rear direction, and every other head module 50 is arranged by shifting the position in the left-right direction (sub-scanning direction).

  The head module 50 is a share mode type. The head module 50 has an ink chamber (not shown) that stores ink supplied from the ink cartridge 49. In the ink chamber, a plurality of pressure chambers (not shown) communicating with the respective nozzles are provided. In this pressure chamber, a partition between adjacent pressure chambers is formed by two piezoelectric members (not shown) having opposite polarization directions. Electrodes (not shown) are formed in close contact with the partition walls between the pressure chambers. When the drive voltage is applied to the electrode, the partition wall is sheared and the volume of the pressure chamber and the pressure in the pressure chamber change. Thereby, the ink in a pressure chamber is discharged from a nozzle.

  The head driving unit 47 drives the inkjet head 46. Specifically, the head driving unit 47 drives the pressure chamber by applying a driving voltage to the electrodes in the head module 50 of the ink jet head 46 to discharge ink from the nozzles.

  The ink cartridge mounting portion 48 is for mounting the ink cartridge 49. The ink cartridge mounting portion 48 is configured such that the ink cartridge 49 can be attached and detached. The ink cartridge mounting unit 48 includes an ink information reading unit 51.

  The ink information reading unit 51 reads ink information from a tag (not shown) of the ink cartridge 49. The ink information includes information indicating the ink color of the ink cartridge 49.

  The ink cartridge 49 contains ink used for printing. The ink cartridges 49K, 49C, 49M, and 49Y contain black, cyan, magenta, and yellow inks, respectively. A tag (not shown) holding ink information is attached to the ink cartridge 49. The ink cartridge 49 can be attached to and detached from the ink cartridge mounting portion 48.

  The upper surface transport unit 4 transports the paper P transported by the belt transport unit 31 in a U-turn from the right direction to the left direction. The upper surface transport unit 4 includes a plurality of pairs of upper surface transport rollers 55.

  The upper surface transport roller 55 transports the paper P along the transport path. The most downstream upper surface conveyance roller 55 is disposed in the upstream portion of the reversing path RR. The other upper surface transport rollers 55 are arranged along the normal path RC between the belt transport unit 31 and the paper discharge unit 5. The upper surface conveyance roller 55 is driven by a motor (not shown).

  The paper discharge unit 5 discharges the printed paper P. The paper discharge unit 5 includes a switching unit 56, a paper discharge roller 57, and a paper discharge stand 58.

  The switching unit 56 switches the transport path of the paper P between the paper discharge path RD and the reverse path RR. The switching unit 56 is disposed at a branch point between the paper discharge route RD and the reverse route RR. The switching unit 56 is driven by a solenoid (not shown).

  The paper discharge roller 57 conveys the paper P guided to the paper discharge path RD by the switching unit 56 and discharges it to the paper discharge stand 58. The paper discharge roller 57 is disposed between the switching unit 56 and the paper discharge stand 58 along the paper discharge path RD. The paper discharge roller 57 is driven by a motor (not shown).

  The paper discharge table 58 is for stacking printed paper P discharged by the paper discharge roller 57. The paper discharge table 58 has a tray shape protruding from the housing 11 and is inclined.

  The reversing unit 6 reverses the single-side printed paper P and conveys it to the registration roller 26 during double-sided printing. The reversing unit 6 includes a reversing roller 61, a switchback unit 62, a refeed roller 63, and a switching gate 64.

  The reversing roller 61 temporarily transports the paper P, which has been transported by the top surface transport roller 55 of the top surface transport unit 4, to the switchback unit 62 and then transports it to the refeed roller 63. The reversing roller 61 is arranged on a reversing path RR between the most downstream upper surface conveying roller 55 and the carry-in port of the switchback unit 62. The reverse roller 61 is driven by a motor (not shown).

  The switchback unit 62 is a space for the reversing roller 61 to temporarily carry in the paper P. The switchback unit 62 is formed at the lower part of the paper discharge table 58. The switchback unit 62 is opened in the vicinity of the reversing roller 61 for carrying the paper P therein.

  The refeed roller 63 transports the paper P transported by the reverse roller 61 to the registration roller 26. The refeed roller 63 is disposed on the reverse path RR between the reverse roller 61 and the registration roller 26. The refeed roller 63 is driven by a motor (not shown).

  The switching gate 64 guides the paper P conveyed by the upper surface conveyance roller 55 to the reverse roller 61. Further, the switching gate 64 guides the paper P carried out from the switchback unit 62 by the reversing roller 61 to the refeed roller 63. The switching gate 64 is disposed in the vicinity of the center of gravity at the three locations of the uppermost transport roller 55, the reverse roller 61, and the refeed roller 63 on the most downstream side.

  The image reading unit 7 optically reads a document and generates image data. The image reading unit 7 includes a document table, a light receiving element, a light source, a lens, a scanning mechanism, an automatic document feeder (all not shown), and the like.

  The operation panel unit 8 accepts user input operations and displays various types of information. The operation panel unit 8 includes an input unit having operation buttons and a touch panel for a user to perform various input operations, a display unit (not shown) including a liquid crystal display panel that displays various types of information, and the like. Is provided.

  The storage unit 9 includes an HDD (Hard Disk Drive) or the like. The storage unit 9 stores various programs and the like. The storage unit 9 includes an image adjustment value storage unit 71. The image adjustment value storage unit 71 stores image adjustment values corresponding to ink of a preset color in each of the inkjet heads 46A to 46D. That is, the image adjustment value storage unit 71 includes an image adjustment value corresponding to black ink in the inkjet head 46A, an image adjustment value corresponding to cyan ink in the inkjet head 46B, an image adjustment value corresponding to magenta ink in the inkjet head 46C, and an inkjet. The image adjustment value corresponding to the yellow ink in the head 46D is stored. These image adjustment values are calculated by an image adjustment process described later when the inkjet printing apparatus 1 is manufactured.

  In addition, the image adjustment value storage unit 71 has an area in which image adjustment values other than the above-described image adjustment values can be additionally stored. For example, the image adjustment value storage unit 71 can store the image adjustment value corresponding to the red (R) ink in the inkjet head 46C in addition to the image adjustment values described above.

  The image adjustment value includes an ink ejection timing correction value and a head drive voltage correction value.

  The ink ejection timing correction value is a value for adjusting the ink landing position. The ink ejection timing correction value is a correction value for the reference value of the ink ejection timing for each line. The reference value of the ink discharge timing is a reference value of the time from the timing when the leading edge of the paper is detected by the paper sensor 32 to the timing at which ink is discharged to each line in each head module 51. The reference value of the ink ejection timing is a value determined based on the design value of the distance from the paper sensor 32 to the nozzle of each head module 51 in the conveyance direction (left-right direction) of the paper P by the belt conveyance unit 31. The ink ejection timing correction value is set for each head module 50.

  The head drive voltage correction value is a value for adjusting the print density. The head driving voltage correction value is a correction value for the reference value of the head driving voltage. The reference value of the head driving voltage is a value of a voltage applied to the pressure chamber electrode of the head module 50 in order to eject a predetermined amount of ink droplets.

  The head drive voltage correction value is the sum of the head module inter-module density correction value, the joint density correction value, and the head module internal density correction value. The head drive voltage correction value is set for each nozzle (pressure chamber) of each head module 50.

  The inter-head module density correction value is a driving voltage correction value for reducing a density difference between adjacent head modules 50 in the same inkjet head 46. The density difference between the adjacent head modules 50 is due to individual differences between the head modules 50.

  The joint density correction value is a drive voltage correction value for reducing density unevenness that occurs at a joint between adjacent head modules 50. The density unevenness that occurs at the joint portion is caused by the displacement of the mounting position of the head module 50 in the main scanning direction (front-rear direction). If the head module 50 is misaligned in the main scanning direction, the pitch of the nozzles is wider or narrower than the predetermined pitch at the joint. As a result, density unevenness (streaks) occurs at a position corresponding to the joint portion in the printed image. The joint density correction value is for increasing or decreasing the amount of ink discharged from the nozzles at the joint part in order to reduce such density unevenness.

  The in-head module density correction value is a driving voltage correction value for reducing density unevenness in the same head module 50. The density unevenness in the same head module 50 is caused by individual differences of nozzles (pressure chambers).

  The control unit 10 controls the operation of each unit of the inkjet printing apparatus 1. The control unit 10 includes a CPU, a RAM, a ROM, and the like.

  When the ink ejected by the inkjet head 46 is changed from a preset color ink to another color ink, the control unit 10 performs the ink adjustment after the change in the inkjet head 46 by an image adjustment process described later. An image adjustment value corresponding to is acquired. The control unit 10 adds the acquired image adjustment value to the image adjustment value storage unit 71. The control unit 10 corresponds to an image adjustment value acquisition unit in claims.

  Next, a printing operation in the inkjet printing apparatus 1 will be described.

  When printing is performed in the inkjet printing apparatus 1, the unprinted paper P is conveyed from one of the external paper feed tray 21 and the plurality of internal paper feed trays 23 of the paper feed unit 2 to the registration roller 26. P is conveyed to the belt conveyance unit 31. The paper P is printed by ink ejected from the inkjet heads 46 </ b> A to 46 </ b> D while being transported by the belt transport unit 31. The printed paper P is conveyed from the belt conveyance unit 31 to the upper surface conveyance unit 4, and is conveyed by the upper surface conveyance roller 55 in the upper surface conveyance unit 4.

  Here, in the case of single-sided printing, the paper P is guided from the normal route RC to the paper discharge route RD by the switching unit 56 of the paper discharge unit 5. Then, the paper P is discharged to a paper discharge tray 58 by a paper discharge roller 57.

  On the other hand, in the case of duplex printing, the paper P is guided from the normal route RC to the reverse route RR by the switching unit 56 of the paper discharge unit 5. The paper P guided to the reversing path RR is guided to the reversing roller 61 by the switching gate 54 in the reversing unit 6, and is carried into the switchback unit 62 by the reversing roller 61. Thereafter, the paper P is unloaded from the switchback unit 62 by the reversing roller 61 and guided to the refeed roller 53 by the switching gate 54. Then, the paper P is conveyed to the registration roller 26 by the refeed roller 53 and is conveyed to the belt conveyance unit 31 by the registration roller 26.

  Here, since the paper P is reversed by the reversing unit 6, the unprinted surface is facing upward. The sheet P is printed on the unprinted surface by the ink ejected from the inkjet heads 46 </ b> A to 46 </ b> D while being conveyed by the belt conveyance unit 31. Then, the double-side printed paper P is transported to the paper discharge unit 5 by the upper surface transport unit 4, and is discharged to the paper discharge tray 58 in the paper discharge unit 5.

  In the above-described printing operation, the control unit 10 performs ink ejection control in each of the inkjet heads 46A to 46D using the image adjustment value corresponding to each of the inkjet heads 46A to 46D stored in the image adjustment value storage unit 71. .

  Specifically, when the paper sensor 32 detects the leading edge of the paper P, the control unit 10 starts counting the number of output pulses of the encoder 42. Based on the count value, the control unit 10 controls each head module 50 so that ink is ejected at a timing shifted by the ink ejection timing correction value with respect to the ink ejection timing reference value for each line. Further, the control unit 10 drives each pressure chamber of each head module 50 with a drive voltage that is increased or decreased by the head drive voltage correction value with respect to the reference value of the head drive voltage.

  Next, the operation when changing the ink color in the inkjet head 46 will be described.

  In the ink jet printing apparatus 1, the ink color ejected by the ink jet head 46 may be changed from a preset ink color. The operation when changing the ink color will be described with reference to the flowchart of FIG. Here, it is assumed that the ink ejected by the inkjet head 46C may be changed from magenta to red.

  In step S1 of FIG. 5, the control unit 10 determines whether or not to change the ink color in the inkjet head 46C. When the magenta ink cartridge 49M is replaced with the red ink cartridge 49R in the ink cartridge mounting unit 48C, the control unit 10 determines to change the ink color.

  Here, an operator such as a service person attaches and detaches the ink cartridge 49. The control unit 10 acquires ink information from the ink information reading unit 51 of the ink cartridge mounting unit 48C, and determines whether or not the magenta ink cartridge 49M has been replaced with a red ink cartridge 49R based on the ink information.

  If it is determined that the ink color is not changed (step S1: NO), the control unit 10 repeats step S1.

  When it is determined that the ink color is to be changed (step S1: YES), in step S2, the control unit 10 performs an ink replacement process. The ink replacement process is a process of replacing the magenta ink remaining in the head module 50 and the ink path of the inkjet head 46C with the red ink when the ink cartridge is replaced.

  Specifically, the control unit 10 executes printing out. In the printing-out, a solid image that consumes a lot of ink is continuously printed. The ink in the ink module 49R and the ink path of the ink jet head 46C is gradually replaced from magenta ink to red ink by supplying red ink from the ink cartridge 49R to the ink path while ink is consumed by printing. When the ink in the head module 50 and the ink path of the ink jet head 46C is completely replaced with the red ink from the magenta ink, the ink replacement process ends.

  Next, in step S3, the control unit 10 performs image adjustment processing. Since the ejection characteristics differ for each ink, when the ink color is changed, an image adjustment value corresponding to the changed ink is required. The image adjustment process is a process of acquiring an image adjustment value corresponding to the ink after the ink color change in the inkjet head 46 in which the ink color change has been performed.

  Specifically, the control unit 10 causes the ink landing positions 46A to 46D to print a pattern image for adjusting the ink landing position. At this time, the control unit 10 uses reference values as the ink ejection timing and the head drive voltage in the inkjet head 46C. The pattern image for adjusting the ink landing position is a pattern image for obtaining an ink ejection timing correction value.

  The paper P on which the pattern image for adjusting the ink landing position is printed is set in the image reading unit 7 by the operator after being discharged. Then, the operator performs an operation to instruct the operation panel unit 8 to read an image by the image reading unit 7.

  In response to this, the control unit 10 causes the image reading unit 7 to read the print image of the pattern image. The image reading unit 7 generates read image data of a print image of a pattern image. Then, the control unit 10 analyzes the read image data and calculates an ink ejection timing correction value corresponding to the red ink in the inkjet head 46C.

  Subsequently, the control unit 10 causes the inkjet head 46C to print a pattern image for adjusting print density. At this time, the control unit 10 performs printing using the ink ejection timing correction value corresponding to the previously calculated red ink. The pattern image for print density adjustment includes each pattern image for obtaining the inter-head module density correction value, the joint density correction value, and the in-head module density correction value.

  Thereafter, similarly, the control unit 10 analyzes the read image data generated by causing the image reading unit 7 to read the print image of the pattern image, and determines the inter-head module density correction value, the joint density correction value, and the inside of the head module. A density correction value is calculated. Then, the control unit 10 calculates, as the head drive voltage correction value, a sum of the inter-head module density correction value, the joint density correction value, and the in-head module density correction value. As a result, the image adjustment process ends.

  Next, in step S4, the control unit 10 stores the ink ejection timing correction value and the head driving voltage correction value calculated in step S3 in the image adjustment value storage unit 71 as image adjustment values corresponding to red ink in the inkjet head 46C. Add and save.

  In subsequent printing operations, the control unit 10 uses the image adjustment value corresponding to the red ink stored in the image adjustment value storage unit 71 as the image adjustment value of the inkjet head 46C.

  When the ink color ejected by the inkjet head 46C is returned from red to magenta, the control unit 10 performs printing using the image adjustment value corresponding to the red ink stored in the image adjustment value storage unit 71. Further, when the ink color ejected by the inkjet head 46C is changed again from magenta to red, the control unit 10 calculates an image corresponding to the red ink calculated and added to the image adjustment value storage unit 71 when the ink color is changed for the first time. Printing is performed using the adjustment value. Therefore, after the first ink color change, image adjustment processing is not necessary in the ink color exchange between magenta and red in the inkjet head 46C.

  As described above, in the inkjet printing apparatus 1, the image adjustment value storage unit 71 additionally adds other image adjustment values other than the image adjustment values corresponding to the preset color inks in the inkjet heads 46 </ b> A to 46 </ b> D. It can be saved. When the ink ejected by the inkjet head 46 is changed from a preset color ink to another color ink, the control unit 10 sets an image adjustment value corresponding to the changed ink in the inkjet head 46. get. Then, the control unit 10 adds the acquired image adjustment value to the image adjustment value storage unit 71.

  Thus, even after the ink color is changed, the image adjustment value corresponding to the ink color before the change is stored in the image adjustment value storage unit 71. This eliminates the need for image adjustment processing when returning to the original ink after changing the ink color. Furthermore, even when the ink color is changed again after returning to the original ink, the image adjustment processing is not necessary. As a result, it is possible to reduce the situation in which the inkjet printing apparatus 1 cannot be used because of the image adjustment process. Therefore, according to the inkjet printing apparatus 1, it is possible to reduce the decrease in convenience when the ink color is changed.

(Second Embodiment)
Next, a description will be given of a second embodiment in which the process for obtaining the image adjustment value when changing the ink color in the first embodiment is changed.

  In the second embodiment, the control unit 10 sets the image adjustment value corresponding to the changed ink in the inkjet head 46 whose ink color has been changed to the image adjustment value corresponding to the color ink set in advance in the inkjet head 46. Based on the correlation with The control unit 10 adds the calculated image adjustment value to the image adjustment value storage unit 71 and stores it.

  For example, when the ink ejected from the inkjet head 46C is changed from magenta to red, the control unit 10 correlates the image adjustment value corresponding to the red ink in the inkjet head 46C with the image adjustment value corresponding to the magenta ink. Calculate based on the relationship.

  Specifically, the control unit 10 calculates an ink ejection timing correction value Tr and a head drive voltage correction value Vr corresponding to red ink in the inkjet head 46C by the following equations (1) and (2).

Tr = αTm (1)
Vr = βVm (2)
Here, Tm is an ink ejection timing correction value corresponding to magenta ink in the inkjet head 46C. Vm is a head driving voltage correction value corresponding to magenta ink in the inkjet head 46C. The ink ejection timing correction value Tm and the head drive voltage correction value Vm are stored in the image adjustment value storage unit 71 in advance.

  As described above, the ink ejection timing correction values Tr and Tm are set for each head module 50. The head drive voltage correction values Vr and Vm are set for each nozzle (pressure chamber) of each head module 50.

  Α and β in equations (1) and (2) are constants. α and β are values determined based on experiments, for example.

  As described above, in the second embodiment, the control unit 10 obtains the image adjustment value corresponding to the changed ink in the inkjet head 46 whose ink color has been changed by calculation. This eliminates the need for image adjustment processing when changing the ink color. As a result, even if the ink color is changed, there is no situation in which the inkjet printing apparatus 1 cannot be used because the image adjustment process is in progress. Therefore, according to the second embodiment, it is possible to further reduce the decrease in convenience when the ink color is changed.

(Third embodiment)
Next, a description will be given of a third embodiment in which the processing for saving the image adjustment value acquired when the ink color is changed in the second embodiment is changed.

  In the third embodiment, as in the second embodiment, the control unit 10 sets an image adjustment value corresponding to the changed ink in the inkjet head 46 whose ink color has been changed to a color preset in the inkjet head 46. It is calculated based on the correlation with the image adjustment value corresponding to the ink.

  Then, the control unit 10 replaces the image adjustment value before the ink color change stored in the image adjustment value storage unit 71 with the image adjustment value corresponding to the calculated ink after the ink color change. In other words, the control unit 10 overwrites and stores the image adjustment value corresponding to the ink after the ink color change with respect to the image adjustment value before the ink color change stored in the image adjustment value storage unit 71.

  In the ink-jet head 46 whose ink color has been changed, when the ink is returned to the original color, the control unit 10 stores the image adjustment value storage unit 71 after changing the ink color based on the above-described correlation. The image adjustment value corresponding to the original color ink is calculated from the image adjustment value corresponding to the current ink. Then, the control unit 10 saves the calculated image adjustment value corresponding to the original color ink overwriting the image adjustment value corresponding to the ink after the ink color change saved in the image adjustment value saving unit 71. To do.

  For example, it is assumed that the ink color is changed from magenta to red in the inkjet head 46C and then returned from magenta to red. In this case, when the ink color is changed from magenta to red, the control unit 10 calculates the image adjustment value corresponding to the red ink using the equations (1) and (2), and uses the image adjustment value storage unit 71. The image adjustment value corresponding to the magenta ink is overwritten and saved.

  When the ink color is returned from red to magenta in the inkjet head 46C, the control unit 10 calculates the ink ejection timing correction value Tm and the head drive voltage correction value corresponding to magenta ink by the following equations (3) and (4). Vm is calculated. Here, the ink ejection timing correction value Tr and the head drive voltage correction value Vr corresponding to the red ink are stored in the image adjustment value storage unit 71 as described above. Equations (3) and (4) are derived from equations (1) and (2).

Tm = Tr / α (3)
Vm = Vr / β (4)
Then, the control unit 10 overwrites and stores the image adjustment value corresponding to magenta ink over the image adjustment value corresponding to red ink stored in the image adjustment value storage unit 71.

  Thus, in the third embodiment, the control unit 10 acquires the image adjustment value corresponding to the ink after the ink color change by calculation, and the image before the ink color change stored in the image adjustment value storage unit 71. The adjustment value is replaced with an image adjustment value corresponding to the ink after changing the ink color. The control unit 10 performs the same process in the case of changing the ink color for returning the ink color that has been changed once.

  For this reason, according to the third embodiment, even in the case where the image adjustment value storage unit 71 does not have an area for adding the image adjustment value, the case of changing the ink color for returning the ink color that has been changed once is also included. There is no need for image adjustment processing when changing the ink color. Therefore, a situation in which the ink jet printing apparatus 1 cannot be used during the image adjustment process does not occur. Therefore, according to the third embodiment, even when the image adjustment value cannot be additionally stored, it is possible to reduce the decrease in convenience when the ink color is changed.

(Other embodiments)
As described above, the present invention has been described according to the first to third embodiments. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the first to third embodiments described above, the inkjet printing apparatus having four inkjet heads has been described. However, the present invention is not limited to this, and any inkjet printing apparatus having at least one inkjet head may be used.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

DESCRIPTION OF SYMBOLS 1 Inkjet printing apparatus 2 Paper feed part 3 Conveyance printing part 4 Upper surface conveyance part 5 Paper discharge part 6 Inversion part 7 Image reading part 8 Operation panel part 9 Storage part 10 Control part 33 Printing part 46A, 46B, 46C, 46D Inkjet head 47 Head drive unit 48A, 48B, 48C, 48D Ink cartridge mounting unit 49K, 49C, 49M, 49Y, 49R Ink cartridge 50 Head module 51 Ink information reading unit 71 Image adjustment value storage unit

Claims (3)

A printing unit having at least one inkjet head, and printing an image by ejecting ink from the inkjet head;
An image adjustment value storage unit that stores image adjustment values corresponding to inks of a preset color in each of the inkjet heads, and that can additionally store other image adjustment values;
When the ink ejected by the inkjet head is changed from a preset color ink to another color ink, the image adjustment value corresponding to the changed ink in the inkjet head is acquired and acquired. An ink-jet printing apparatus comprising: an image adjustment value acquisition unit that adds an image adjustment value to the image adjustment value storage unit.   The image adjustment value acquisition unit sets in advance an image adjustment value corresponding to the changed ink in the ink jet head whose ink color has been changed, which is stored in the image adjustment value storage unit in advance. 2. The ink jet printing apparatus according to claim 1, wherein calculation is performed based on a correlation with image adjustment values corresponding to inks of different colors. A printing unit having at least one inkjet head, and printing an image by ejecting ink from the inkjet head;
In each of the inkjet heads, an image adjustment value storage unit that stores an image adjustment value corresponding to the ink ejected by the inkjet head;
When the ink color discharged from the inkjet head is changed, the image adjustment value corresponding to the changed ink in the inkjet head is stored in the image adjustment value storage unit. The image adjustment value before the change of the ink color calculated based on the correlation with the image adjustment value before the change and the image adjustment value before the change of the ink color stored in the image adjustment value storage unit is calculated according to the calculated ink after the change. An ink-jet printing apparatus comprising: an image adjustment value acquisition unit that replaces a value.