JP2019107809A - Inkjet recording device - Google Patents

Abstract

To prevent jetting defects of ink in a plurality of nozzles while maintaining good printing quality.SOLUTION: A time deriving part 711c derives, for each of nozzles, duration time in a no-jetting state in which ink is not jetted, no-jetting time which is initiated every time when ink is jetted. A compression control part 711b sets a jetting-control value, a control value of each of compressing parts 30C at the time of jetting ink from each of the nozzles, according to a pixel value of image data and the no-jetting time. The compression control part 711b, when the no-jetting time is in a predetermined first time range, sets the jetting-control value to a standard value corresponding to the pixel value, and when the no-jetting time is in a second time range longer than the first time range, sets the jetting-control value to a value larger than the standard value.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an inkjet recording apparatus having a plurality of nozzles for ejecting ink.

  An inkjet recording apparatus that forms an image on a sheet by an inkjet method includes a plurality of nozzles that eject ink. Each of the nozzles may continue in a non-jetting state in which ink is not ejected during the printing process.

  In the nozzle in which the non-jetting state continues for a predetermined time or more, the ink dries and the viscosity of the ink increases. As a result, when the nozzle ejects the ink after the non-ejection state, ejection failure of the ink tends to occur.

  The ejection failure is a failure such that the ink is not ejected or the ejection amount of the ink is insufficient. Usually, when a control value corresponding to a relatively small amount of ink is set, the problem of the ejection failure easily occurs.

  For example, in order to solve the problem of the ejection failure of the ink, it is known to make each of the nozzles perform a preliminary ejection of the ink (see, for example, Patent Document 1). The preliminary ejection is to eject ink from the nozzle at a timing not contributing to drawing based on image data when the non-ejection state continues for a predetermined time or more.

JP, 2011-177898, A

  By the way, when the nozzle is caused to perform the preliminary ejection, the ink is ejected to the area which should become blank on the sheet. As a result, print quality may be degraded.

  An object of the present invention is to provide an ink jet recording apparatus capable of preventing ejection failure of ink at a plurality of nozzles while maintaining good print quality.

  An ink jet recording apparatus according to one aspect of the present invention includes a plurality of nozzles, a plurality of pressure units, a time derivation unit, and a pressure control unit. The plurality of pressurizing units correspond to the plurality of nozzles, and press the ink to eject the ink from the plurality of nozzles. The time deriving unit is a continuation time of a non-jetting state in which the ink is not jetted for each of the nozzles, and derives a non-jetting time which is initialized each time the ink is jetted. The pressure control unit sets a jet control value, which is a control value of each pressure unit when jetting the ink from each of the nozzles, according to a pixel value of image data to be printed and the non-jet time. Do. The pressurization control unit sets the ejection control value to a standard value corresponding to the pixel value when the non-ejection time belongs to a predetermined first time range, and the non-ejection time is the first The ejection control value is set to a value larger than the standard value when it belongs to a second predetermined time range which is a time range longer than the time range.

  According to the present invention, it is possible to provide an inkjet recording apparatus capable of preventing ejection failure of ink at a plurality of nozzles while maintaining good print quality.

FIG. 1 is a block diagram of the ink jet recording apparatus according to the embodiment. FIG. 2 is a block diagram of an ink jet unit in the ink jet recording apparatus according to the embodiment. FIG. 3 is a block diagram of a control device in the ink jet printing apparatus according to the embodiment. FIG. 4 is a flowchart illustrating an example of the procedure of the ink ejection control in the inkjet recording apparatus according to the embodiment. FIG. 5 is a view schematically showing the relationship between the non-ejection time and the pre-vibration time set in the ink ejection control, and the drawing pixel. FIG. 6 is a view showing an example of the data configuration of the control value look-up table in the ink jet printing apparatus according to the embodiment. FIG. 7 is a view showing an example of the configuration of table selection data in the ink jet printing apparatus according to the embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The following embodiment is an example embodying the present invention, and does not have the property of limiting the technical scope of the present invention.

[Configuration of inkjet recording apparatus 10]
The inkjet recording apparatus 10 is a printer capable of executing printing processing by an inkjet method. The printing process is a process of forming an image on the sheet 9. The sheet 9 is a sheet-like image forming medium such as paper or a resin film.

  It is also conceivable that the inkjet recording apparatus 10 is a facsimile apparatus, a copier, a multifunction apparatus, or the like that can execute the printing process by the inkjet method.

  As shown in FIG. 1, the inkjet recording apparatus 10 includes a sheet storage unit 1, a sheet supply mechanism 2, an inkjet unit 3, an ink supply unit 4, a conveyance device 5, a sheet discharge mechanism 6, a control device 7 and the like.

  The sheet storage unit 1 can store a plurality of sheets 9. The sheet supply mechanism 2 conveys the sheets 9 stored in the sheet storage unit 1 to the transport device 5 one by one.

  The conveying device 5 conveys the sheet 9 in a predetermined conveyance direction D0 while making the surface of the sheet 9 face the inkjet unit 3. The direction orthogonal to the transport direction D0 is the main scanning direction D1, and the opposite direction of the transport direction D0 is the sub-scanning direction D2 (see FIGS. 1 and 2).

  The inkjet unit 3 forms an image on the sheet 9 by ejecting the four color inks toward the sheet 9 conveyed by the conveying device 5.

  The transport device 5 is disposed below the inkjet unit 3. In the conveyance device 5, the tension rollers 52 to 54 rotate while supporting the conveyance belt 51. The conveyance belt 51 places the sheet 9 and conveys the sheet 9 in the conveyance direction D0. Further, the conveyance belt 51 sends the sheet 9 on which the image is formed to the sheet discharge mechanism 6.

  The sheet discharging mechanism 6 is provided downstream of the transport device 5 in the transport direction D0. In the sheet discharge mechanism 6, the discharge roller 61 discharges the sheet 9 on which the image is formed to the discharge tray 62.

[Ink jet part 3]
The inkjet unit 3 forms an image on the sheet 9 by ejecting ink to the sheet 9 conveyed by the conveyance device 5. The inkjet unit 3 includes line heads 31, 32, 33, 34 corresponding to the respective colors of black, cyan, magenta and yellow.

  Four line heads 31, 32, 33, 34 correspond to black, cyan, magenta and yellow inks, respectively. That is, the four line heads 31, 32, 33, 34 correspond to inks of different colors, respectively.

  The four line heads 31, 32, 33, 34 are arranged side by side in the sub scanning direction D2 and fixed in a predetermined positional relationship (see FIGS. 1 and 2). In addition, it is also considered that the number of the said line head with which the inkjet part 3 is provided is three or five or more.

  The four line heads 31, 32, 33, 34 are disposed at positions where a gap of about 1 millimeter is formed between their ink output surfaces 30A and the upper surface of the sheet 9 on the transport belt 51.

  As shown in FIG. 2, the line heads 31 to 34 are arranged such that their longitudinal directions are along the main scanning direction D1. Each of the line heads 31 to 34 has a plurality of nozzles 30B arranged in a range over the entire effective area in the main scanning direction D1 of the sheet 9 of the maximum size that can be accommodated by the sheet accommodation unit 1.

  In each of the line heads 31 to 34, the plurality of nozzles 30B eject ink to a plurality of pixel positions in one line in the main scanning direction D1 with respect to the sheet 9 conveyed in the conveyance direction D0.

  The effective area of the sheet 9 is the remaining area excluding the minimum margin area of a predetermined width at both ends of the main scanning direction D1 from the entire range in the main scanning direction D1 of the sheet 9. When the width of the minimum margin area is zero, the entire range in the main scanning direction D1 of the sheet 9 is the effective area.

  In the example shown in FIG. 2, each of the line heads 31 to 34 has a plurality of inkjet heads 30. The plurality of inkjet heads 30 each have a plurality of nozzles 30B.

  In each of the line heads 31 to 34, the plurality of nozzles 30B eject ink to a part of the effective area in the main scanning direction D1, respectively. Further, all the nozzles 30B in all the line heads 31 to 34 correspond one-to-one to all pixel positions of one line in the main scanning direction D1 in the effective area.

  That is, in each of the line heads 31 to 34, the plurality of nozzles 30B eject ink for each pixel to different pixel positions in the effective area in the main scanning direction D1.

  In addition, each of the inkjet heads 30 includes a plurality of piezoelectric elements 30C corresponding to the plurality of nozzles 30B (see FIG. 3). The plurality of piezoelectric elements 30C correspond to the plurality of nozzles 30B on a one-to-one basis.

  Each of the piezoelectric elements 30C vibrates in response to the drive signal Sd0 supplied from the control device 7 to pressurize the ink. The drive signal Sd0 is a pulse width modulated continuous pulse signal. Each of the piezoelectric elements 30C ejects ink from each of the nozzles 30B by pressing the ink.

  Each of the piezoelectric elements 30C is an example of a pressing unit that ejects the ink from each of the nozzles 30B by pressing the ink.

  Specifically, each of the inkjet heads 30 includes a plurality of pressure chambers (not shown) corresponding to the plurality of nozzles 30B. Each of the piezoelectric elements 30C presses the ink stored in each of the pressure chambers by being driven by the drive signal Sd0. As a result, the ink in the pressure chamber flows into the nozzle 30B, and is jetted toward the sheet 9 from the opening of the nozzle 30B.

[Control device 7]
As shown in FIG. 3, the controller 7 includes a main controller 71, a drive circuit 72, and a temperature and humidity sensor 73. The main control device 71 includes a central processing unit (CPU) 711, a random access memory (RAM) 712, a secondary storage device 713, and the like.

  The CPU 711 is a processor that executes a program stored in advance in the secondary storage device 713. The CPU 711 executes various calculations, data processing, and control of various electric devices provided in the inkjet recording apparatus 10.

  The RAM 712 is a main storage device for temporarily storing the program executed by the CPU 711 and data to be output and referred to when the CPU 711 executes the program.

  The secondary storage 713 is a computer readable non-volatile data storage. The secondary storage 713 can store programs and various data. For example, a flash memory or an EEPROM (Electrically Erasable Programmable Read Only Memory) may be adopted as the secondary storage 713.

  In the present embodiment, the CPU 711 operates as the conveyance control unit 711a and the pressurization control unit 711b by executing the program.

  The conveyance control unit 711 a controls the sheet supply mechanism 2, the conveyance device 5, and the sheet discharge mechanism 6. That is, the conveyance control unit 711a controls the conveyance of the sheet 9.

  The pressure control unit 711b controls the ejection amount of each ink by setting the control value of each of the piezoelectric elements 30C. The pressure control unit 711b sets the control values of the plurality of piezoelectric elements 30C according to the plurality of pixel values included in the image data to be printed.

  The piezoelectric element 30C applies a larger pressure to the ink in the pressure chamber as the control value is larger. Therefore, if the ink property such as viscosity is constant, the larger the control value is, the more ink is ejected from the nozzle 30B.

  The pressure control unit 711 b outputs a control signal Sc 0 of a level corresponding to the control value to the drive circuit 72 through the I / O port 711 x of the CPU 711. The I / O port 711x is a signal input / output interface device.

  The drive circuit 72 outputs a plurality of drive signals Sd0 to the plurality of piezoelectric elements 30C in accordance with the control signal Sc0. At this time, the drive circuit 72 performs PWM (Pulse Width Modulation) control of the plurality of drive signals Sd0 in accordance with the level of the control signal Sc0. Thus, the drive circuit 72 controls the amount of ink ejected to the plurality of nozzles 30B by the PWM control.

  The temperature and humidity sensor 73 detects the temperature and humidity of the environment in which the inkjet recording device 10 is installed. The CPU 711 acquires the detection result of the temperature and humidity sensor 73 through the I / O port 711x.

  In each of the nozzles 30B, a non-jetting state in which the ink is not jetted may continue during the continuous printing process. The continuous printing process is the continuous printing process on a plurality of sheets 9. In each of the nozzles 30B, when the ink is ejected after the non-ejection state continues for a predetermined time or more, ejection failure of the ink tends to occur.

  The ejection failure is a failure such that the ink is not ejected or the ejection amount of the ink is insufficient. Usually, when the control value corresponding to a relatively small amount of ink is set, the problem of the ejection failure easily occurs.

  By the way, when each nozzle 30B is caused to perform preliminary ejection of the ink, the ink is ejected to an area in the sheet 9 which should be blank. As a result, print quality may be degraded.

  The preliminary ejection is to eject ink from each of the nozzles 30B at a timing that does not contribute to the drawing based on the image data, for example, when the non-ejection state of the nozzles 30B continues for a predetermined time or more. The non-jetting state is a state in which the nozzle 30B does not eject ink during the printing process.

  In the inkjet recording apparatus 10, the pressure control unit 711b and the time deriving unit 711c described later execute ink ejection control described later. Thereby, the inkjet recording apparatus 10 can prevent the ejection failure of the ink in the plurality of nozzles 30B while maintaining good print quality.

  The CPU 711 also operates as a time deriving unit 711 c by executing a program stored in advance in the secondary storage device 713. In the ink ejection control, the time deriving unit 711c derives the non-ejection time TX0 (i) and the pre-vibration time TY0 (i).

  The non-jetting time TX0 (i) is a continuation time of the non-jetting state in which the ink is not jetted in each of the nozzles 30B, and is a time which is initialized each time the ink is jetted.

  In other words, the non-ejection time TX0 (i) is a continuation time of the state in which the ink is not ejected from the corresponding nozzle 30B in each of the piezoelectric elements 30C, and vibration causing the ink to be ejected from the corresponding ink is It is a time that is initialized each time it occurs.

  In the present embodiment, the preliminary ejection not contributing to the drawing based on the image data is not performed. Therefore, the non-ejection time is determined according to the number of continuous pixel values of density zero in the sub scanning direction D2 in the image data.

  The element number i, which is a subscript in the non-ejection time TX0 (i), is an identification number of each of the piezoelectric elements 30C. The element number i is also an identification number of each nozzle 30B.

  In the example shown in FIG. 5, the element number i is continuous corresponding to the pixel position in the main scanning direction D1 for each of the plurality of piezoelectric elements 30C corresponding to the ink of one color among black, cyan, magenta and yellow. Show the case.

  FIG. 5 shows that when the image of the j-th line in the first page of the image data is printed, the 0th piezoelectric element 30C in the main scanning direction D1, the i-th piezoelectric element 30C, and the i + 1th piezoelectric element 30C shows the situation where the ink ejection operation is performed.

  In FIG. 5, the zeroth piezoelectric element 30C performs the ink ejection operation only at the jth line of the first page. In this case, the time from when printing of the first page starts to when the image of the j-th line is printed corresponds to the non-jetting time corresponding to the ink ejection operation at the j-th line by the 0th piezoelectric element 30C. It is TX0 (0).

  In FIG. 5, the i-th piezoelectric element 30C performs the ink ejection operation from the execution of the ink ejection operation on the k1st line of the first page to the ink ejection operation on the jth line. Not performed. In this case, the time from when the image of the k1st line of the first page is printed to when the image of the jth line is printed is the ink ejection operation at the jth line by the ith piezoelectric element 30C. The corresponding non-ejection time TX0 (i).

  Similarly, in FIG. 5, the (i + 1) th piezoelectric element 30C performs the ink ejection operation on the k2nd line of the first page until the ink ejection operation on the jth line is performed. I do not do the action of the spout. In this case, the time from when the image of the k2nd line of the first page is printed to when the image of the jth line is printed is the ink ejection at the jth line by the (i + 1) th piezoelectric element 30C. It is the non-ejection time TX0 (i + 1) corresponding to the operation. In FIG. 5, k2> k1.

  Further, in the present embodiment, a plurality of look-up tables D10 and table selection data D20 used in the ink ejection control are stored in advance in the secondary storage device 713. The contents of these data will be described later.

[Ink ejection control]
Hereinafter, an example of the procedure of the ink ejection control will be described with reference to the flowchart shown in FIG.

  The pressure control unit 711b and the time derivation unit 711c execute the ink ejection control when the continuous printing process is performed. In the following description, S1, S2,... Represent identification codes of a plurality of steps in the ink ejection control.

  FIG. 4 shows the procedure of the ink ejection control for the element number i in the printing process for one page. That is, FIG. 4 shows the procedure of the ink ejection control for the ith piezoelectric element 30C in the printing process for one page.

  The pressure control unit 711b and the time derivation unit 711c execute the ink ejection control in the procedure shown in FIG. 4 for each of all the piezoelectric elements 30C for each page in the image data to be printed.

<Step S1>
In the continuous printing process, the time deriving unit 711c initializes the line number j. The line number j is a variable for specifying the position in the sub scanning direction D2 for each page in the continuous printing process.

<Step S2>
Next, the time derivation unit 711c derives the non-ejection time TX0 (i). The non-ejection time TX0 (i) is the time until the i-th piezoelectric element 30C performs an ink ejection operation next.

  The time derivation unit 711c derives the non-ejection time TX0 (i) by multiplying the number of consecutive pixel values of density zero in the sub-scanning direction D2 in the image data by the line feed time T00.

  A line feed time T00 is a time required for the sheet 9 to advance by the line pitch of the image along the sub scanning direction D2. The line pitch is the spacing between one line and the next in the image.

<Step S3>
Furthermore, the time deriving unit 711c derives the pre-vibration time TY0 (i) based on the pre-vibration time TY0 (i). The pre-vibration time TY0 (i) is a time for vibrating the piezoelectric element 30C with a meniscus. The meniscus vibration is to vibrate the piezoelectric element 30C to such an extent that the ink is not ejected from the nozzle 30B.

  The pressure control unit 711b causes the piezoelectric element 30C to vibrate the meniscus for the pre-vibration time TY0 (i) before causing the piezoelectric element 30C to operate the ink ejection.

  The correspondence between the non-ejection time TX0 (i) and the pre-vibration time TY0 (i) is predetermined. The time derivation unit 711c derives the pre-vibration time TY0 (i) from the non-ejection time TX0 (i) according to the correspondence relationship.

  For example, when the non-ejection time TX0 (i) is equal to or greater than a predetermined lower limit time, the time derivation unit 711c multiplies the non-ejection time TX0 (i) by a coefficient smaller than a predetermined one. It is conceivable to derive the vibration time TY0 (i). Furthermore, when the non-ejection time TX0 (i) is less than the lower limit time, it is conceivable that the time deriving unit 711c derives 0 as the pre-vibration time TY0 (i).

  It is also conceivable that a look-up table representing a correspondence between the non-ejection time TX0 (i) and the pre-vibration time TY0 (i) is set in advance. In this case, the time deriving unit 711c derives the pre-oscillation time TY0 (i) by applying the non-ejection time TX0 (i) to the lookup table.

  FIG. 5 shows the non-ejection time TX0 (0), the non-ejection time TX0 (i) and the non-ejection time TX0 (0) derived for the 0th, i-th and (i + 1) th piezoelectric elements 30C that perform the ink ejection operation with the line of line number j. The non-ejection time TX0 (i + 1) is schematically shown.

  Further, in FIG. 5, since the non-ejection time TX0 (0) is longer than the non-ejection time TX0 (i + 1), the pre-vibration time TY0 (0) is set to be longer than the pre-vibration time TY0 (i + 1) An example is shown.

  Furthermore, FIG. 5 shows an example in which the pre-vibration time TY0 (i) is set to 0 because the non-ejection time TX0 (i) is less than the lower limit time.

<Step S4>
Next, the ejection control value CV0 (i) which is the control value of the piezoelectric element 30C when the pressure control unit 711b ejects the ink from the nozzle 30B, the pixel value of the image data and the non-ejection time TX0 ( Set according to i).

  Specifically, first, the pressure control unit 711b selects one corresponding to the detection result of the temperature and humidity sensor 73 from the plurality of lookup tables D10 based on the table selection data D20. As described above, the plurality of lookup tables D10 and table selection data D20 are stored in advance in the secondary storage device 713.

  As shown in FIG. 6, a plurality of lookup tables D10 are respectively associated with table numbers D14. Further, as shown in FIG. 7, the table selection data D20 indicates the correspondence between a plurality of combinations of the temperature range D21 and the humidity range D22 and a plurality of table numbers D14.

  The pressurization control unit 711b first specifies the combination of the temperature range D21 and the humidity range D22 corresponding to the combination of the temperature and the humidity detected by the temperature and humidity sensor 73, and combines the specified temperature range D21 and the humidity range D22. One corresponding table number D14 is selected.

  Then, the pressure control unit 711b selects one of the plurality of lookup tables D10 that corresponds to the selected table number D14.

  As shown in FIG. 6, each of the look-up tables D10 includes time range information D11 representing a range of non-ejection time TX0 (i), pixel value information D12 representing a candidate of the pixel value, and the ejection control value. It represents the correspondence with the setting value information D13 representing the candidate.

  In each of the look-up tables D10 of FIG. 6, when the non-ejection time TX0 (i) belongs to a first time range less than a predetermined lower limit value MM1, the same setting value as the pixel value is the ejection control value. It indicates that the setting value larger than the pixel value is set to the ejection control value when the non-ejection time TX0 (i) belongs to the second time range from the lower limit value MM1 to the intermediate value MM2 .

  In the present embodiment, the same value as the pixel value is a standard value corresponding to the pixel value.

  The pressurization control unit 711b derives the control value by applying the non-ejection time TX0 (i) and the pixel value to the selected lookup table D10.

  That is, each of the lookup tables D10 represents a derivation rule for deriving the ejection control value from the combination of the non-ejection time TX0 (i) and the pixel value. The pressurization control unit 711b derives the ejection control value CV0 (i) according to the derivation rule represented by the selected lookup table D10.

  The control value is selected from a plurality of gradation values corresponding to a plurality of density levels of a pixel. The plurality of gradation values include a zero value, a pre-oscillation value CV1, and a plurality of ejection values. The zero value corresponds to the pixel value of density zero in the image data, and represents a level at which the piezoelectric element 30C is stopped. The pre-oscillation value represents a level at which the piezoelectric element 30C is oscillated by a meniscus.

  The plurality of ejection values represent levels at which the piezoelectric element 30C is vibrated to such an extent that different amounts of ink are ejected from the nozzles 30B. One of the plurality of ejection values is derived as the ejection control value.

<Step S5>
Next, the pressurization control unit 711b sets the non-ejection time TX0 (i) to the time variable TP0 (i).

<Step S6>
Then, the pressurization control unit 711b shifts the process to step S7 when the time variable TP0 (i) is greater than 0 and is less than or equal to the pre-vibration time TY0 (i), and shifts the process to step S8 otherwise. Let

<Step S7>
In step S7, the pressure control unit 711b sets the pre-vibration value CV1 to the setting value of the ith piezoelectric element 30C. Thereby, the i-th piezoelectric element 30C vibrates in the meniscus.

  By the meniscus vibration of the piezoelectric element 30C, the ink is released. As a result, when the ejection value is set next to the setting value, the ink can be easily ejected normally from the nozzle 30B.

  In FIG. 5, an arrow line corresponding to the pre-vibration time TY0 (0) indicates a period in which the 0-th piezoelectric element 30C vibrates in a meniscus until the image of the line of line number j is printed. Similarly, in FIG. 5, an arrow line corresponding to the pre-vibration time TY0 (i + 1) indicates a period in which the (i + 1) th piezoelectric element 30C vibrates in a meniscus until the image of the line of line number j is printed.

<Steps S8 to S10>
In step S8, the pressure control unit 711b determines whether the time variable TP0 (i) is zero.

  When it is determined that the time variable TP0 (i) is 0, the pressurization control unit 711b sets the ejection control value CV0 (i) as the setting value of the ith piezoelectric element 30C (S9). Thus, the i-th piezoelectric element 30C applies a pressure corresponding to the ejection control value CV0 (i) set in step S4 to the ink.

  That is, in step S9, the pressure control unit 711b causes the ith piezoelectric element 30C to execute the process of ejecting the ink from the ith nozzle 30B. Thus, the ink is ejected from the ith nozzle 30B.

  As described above, when the non-ejection time TX0 (i) is relatively long, the pressure control unit 711b causes the control value such that a pressure larger than the pressure corresponding to the pixel value of the image data is applied to the ink. Is set (see FIG. 6).

  Therefore, in the nozzle 30B in which the non-jetting state continues for a long time, even when the viscosity of the ink is high, it is possible to eject an amount of ink corresponding to the pixel value. As a result, even when the non-jetting state of the nozzle 30B continues for a long time, good print quality can be maintained.

  Furthermore, after setting the ejection control value CV0 (i) to the setting value of the i-th piezoelectric element 30C, the pressure control unit 711b returns the setting value of the i-th piezoelectric element 30C to a zero value (S10) . The initial value of the control value is the zero value. Thereby, the i-th piezoelectric element 30C is stopped.

  On the other hand, if it is determined that the time variable TP0 (i) is not 0, the pressure control unit 711b maintains the set value of the i-th piezoelectric element 30C as the zero value (S10). Thereby, the i-th piezoelectric element 30C does not operate.

<Step S11>
Next, the pressure control unit 711b shifts the process to step S12 when the line number j indicates the middle of printing of each page in the image data. The pressure control unit 711b shifts the process to step S13 when the line number j indicates the end of printing of each page in the image data. Further, the pressure control unit 711b ends the ink ejection control when printing of all pages in the image data is completed.

<Step S12>
In step S12, the time derivation unit 711c counts up the line number j. Furthermore, the time derivation unit 711c updates the time variable TP0 (i) to a value obtained by subtracting the line feed time T00, which is predetermined according to the transport speed of the sheet 9. Thereafter, the time derivation unit 711c shifts the process to step S14.

  A line feed time T00 is a time required to print an image of a line along the sub-scanning direction D2 and to print an image of the next line. The conveying speed of the sheet 9 is generally referred to as linear speed.

<Step S13>
In step S13, the time derivation unit 711c initializes the line number j. Furthermore, the time derivation unit 711c updates the time variable TP0 (i) to a value obtained by subtracting the page change time T01, which is predetermined according to the transport speed of the sheet 9. Thereafter, the time derivation unit 711c shifts the process to step S14.

  The page break time T01 is the time required to print the image of the last line of the image of a page in the image data and to print the image of the first line of the image of the next page.

<Step S14>
In step S14, the pressure control unit 711b relates to the printing process of the line with line number j, and when the process reaches step S14 through step S9 of causing the i-th piezoelectric element 30C to perform the ink ejection operation, the process is performed in step S2. Transition to Thereby, the process from step S2 is repeated.

  On the other hand, the pressure control unit 711b relates to the printing process of the line of the line number j, and when the process S14 is reached without the process S9, the process is transferred to the process S6. Thereby, the process from step S6 is repeated.

  According to the present embodiment, it is possible to prevent the ejection failure of the ink in the plurality of nozzles 30B while maintaining good print quality.

  Further, in the present embodiment, the plurality of lookup tables D10 are a plurality of candidates of derivation rules for deriving the ejection control value CV0 (i) from the pixel value and the non-ejection time TX0 (i) in the image data.

  The plurality of look-up tables D10 are preset corresponding to the plurality of combinations of temperature and humidity.

  Then, in step S4, the pressurization control unit 711b applies the pixel value and the non-ejecting time TX0 (i) to the look-up table D10 corresponding to the detection result of the temperature and humidity sensor 73 so that the ejection control value CV0 (i Derive).

  Therefore, even when the viscosity of the ink fluctuates according to the temperature and humidity, it is possible to derive an appropriate ejection control value CV0 (i) in accordance with the temperature and humidity conditions.

  In general, the viscosity of the ink tends to be higher when the ambient environment is hot and humid than when cold and humid. Therefore, look-up table D10 corresponding to high temperature and high humidity has a larger ejection control value CV0 (i) for the same pixel value than look-up table D10 corresponding to relatively low temperature and low humidity. Represents the rules to be derived.

  Further, in steps S6 and S7, the pressure control unit 711b can set the control value of each of the piezoelectric elements 30C before the ink is ejected from each of the nozzles 30B to the pre-vibration value CV1. As a result, when the ejection control value CV0 (i) is next set to the set value, the ink can be easily ejected normally from the nozzle 30B.

  Furthermore, in step S3, the time deriving unit 711c determines the pre-vibration time TY0 (i) according to the non-ejection time TX0 (i). As described above, the pre-vibration time TY0 (i) is a time for setting the control value to the pre-vibration value CV1 before ejecting ink from each of the nozzles 30B. This can prevent the viscosity of the ink from becoming too high.

[First application example]
In the embodiment described above, the step S3 of setting the pre-vibration time TY0 (i) may be omitted, and the time of setting the control value to the pre-vibration value CV1 may be constant.

Second application example
In the embodiment described above, it is also conceivable that the step S3 of setting the pre-vibration time TY0 (i) and the steps S6 and S7 of setting the control value to the pre-vibration value CV1 may be omitted.

1: sheet storage unit 2: sheet supply mechanism 3: inkjet unit 4: ink supply unit 5: transport device 6: sheet discharge mechanism 7: control device 9: sheet 10: ink jet recording device 30: ink jet head 30 A: ink output surface 30 B : Nozzle 30C: Piezoelectric elements 31 to 34: Line head 51: Conveying belts 52 to 54: Stretching roller 61: Discharge roller 62: Discharge tray 71: Main controller 72: Drive circuit 73: Temperature and humidity sensor 711: CPU
711a: transport control unit 711b: pressure control unit 711c: time derivation unit 711x: I / O port 712: RAM
713: Secondary storage device CV0: Jet control value CV1: Pre-vibration value D0: Transport direction D1: Main scanning direction D10: Look-up table D11: Time range information D12: Pixel value information D13: Setting value information D14: Table number D2 Sub-scanning direction D20: Table selection data D21: Temperature range D22: Humidity range Sc0: Control signal Sd0: Drive signal

Claims (4)

With multiple nozzles,
A plurality of pressure parts corresponding to the plurality of nozzles and causing the ink to be ejected from the plurality of nozzles by pressurizing the ink;
A time deriving unit for deriving a non-jetting time which is a continuation time of the non-jetting state in which the ink is not jetted for each of the nozzles, and which is initialized each time the ink is jetted;
A pressure control unit configured to set an ejection control value, which is a control value of each pressing unit when ejecting the ink from each of the nozzles, according to a pixel value of image data to be printed and the non-ejection time; The pressurization control unit sets the ejection control value to a standard value corresponding to the pixel value when the non-ejection time belongs to a predetermined first time range, and the non-ejection time is the same. An inkjet recording apparatus, wherein the ejection control value is set to a value larger than the standard value when it belongs to a predetermined second time range which is a time range longer than the first time range. Temperature and humidity sensors that detect temperature and humidity,
A plurality of candidates of a derivation rule for deriving the ejection control value from the pixel value and the non-ejection time are set in advance corresponding to a plurality of combinations of temperature and humidity,
The inkjet recording according to claim 1, wherein the pressure control unit derives the ejection control value by applying the pixel value and the non-ejection time to the derivation rule corresponding to the detection result of the temperature and humidity sensor. apparatus. Each of the pressurizing units is a piezoelectric element that vibrates by a drive signal corresponding to the control value,
The pressure control unit sets the control value of each of the pressure units before jetting the ink from each of the nozzles to a pre-vibration value that causes the piezoelectric element to vibrate to such an extent that the ink is not jetted from the nozzles. The ink jet recording apparatus according to claim 1 or 2, which is possible.   The time deriving unit determines a time for setting the control value to the pre-oscillation value before jetting the ink from each of the nozzles, according to the non-jetting time. An ink jet recording apparatus according to any one of the preceding claims.

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