JP2024042362A - Inkjet head driving device, inkjet image formation device, inkjet head driving method, and driving program of inkjet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformize temperature distribution of a plurality of nozzles in an inkjet head using a piezoelectric element.

SOLUTION: An inkjet head driving device for driving respective piezoelectric elements of a plurality of nozzles aligned in a width direction by application of a driving pulse based on image data, and thereby causing the plurality of nozzles to discharge ink and forming an image includes: a first generation part for generating discharge pulse data driving the piezoelectric elements so as to discharge ink from image data; a second generation part for determining temperature distribution in a width direction of the plurality of nozzles by referring to a correspondence between a pixel value of a pixel of the image data or discharge pulse data, and the temperature of the nozzles, determining complementary temperature distribution of complementing the temperature distribution, and generating dummy pulse data driving the piezoelectric element so as not to discharge ink from the complementary temperature distribution; and a third generation part for generating a driving pulse on the basis of the discharge pulse data and the dummy pulse data.

SELECTED DRAWING: Figure 7

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to an inkjet head driving device for driving an inkjet head, an inkjet image forming apparatus, an inkjet head driving method, and an inkjet head driving program.

2. Description of the Related Art Inkjet image forming apparatuses (hereinafter referred to as image forming apparatuses) that use an inkjet head that ejects ink from a plurality of nozzles onto a recording medium such as paper to form (print) an image on the recording medium are known. Inkjet heads (hereinafter referred to as heads) include, for example, a thermal type that prints using a heating element or the like, a piezo type that prints using a piezoelectric element, etc.

In a thermal type head, ink is ejected from a nozzle using bubbles formed by a heating element to which a drive pulse (voltage pulse) is applied. Therefore, there is a problem in that the amount of heat generated by the heating element differs between the nozzles (between the nozzle that prints and the nozzle that does not print), resulting in a temperature difference between the nozzles, which causes the print density to fluctuate.

In order to solve the above problem, in Patent Document 1, a print pulse is applied to the heating element of each nozzle based on the print data, and a dummy drive pulse that raises the temperature without ejecting ink is applied to the heating element based on the inverted data of the print data. In a thermal type head as shown in Patent Document 1, the heating element is relatively small, and the effect of heat transfer to surrounding nozzles is relatively small. Therefore, by applying the above-mentioned dummy drive pulse to each nozzle, it is possible to bring each nozzle to a predetermined temperature and to keep the temperature difference between nozzles within a predetermined range.

JP 2004-268451 A

A piezo head uses the deformation of a piezoelectric element to which a drive pulse (voltage pulse) is applied to eject ink from a nozzle. Since a piezoelectric element to which a drive pulse is applied generates heat, even in a piezo head, there is a problem in that there is a difference in the amount of heat generated between nozzles, a temperature difference occurs between the nozzles, and the print density fluctuates.

Even in a piezo type head, as described above, it is conceivable to apply a dummy drive pulse based on inverted data to the piezoelectric element in addition to a drive pulse based on print data in each nozzle.

However, the elements themselves are different between a thermal type head using a heating element and a piezo type head using a piezoelectric element, for example, the piezoelectric element is larger than the heating element. Therefore, in a piezo head, even if a dummy drive pulse based on inverted data is applied to each nozzle, it is difficult to bring each nozzle to a predetermined temperature, and it is difficult to make the temperature distribution of multiple nozzles uniform. That's difficult. Furthermore, the head itself has a large heat capacity, and there is a time lag between the heat generated by the piezoelectric element due to driving and the actual temperature distribution of the nozzle.

An object of the present invention is to provide an inkjet head driving device, an inkjet image forming apparatus, an inkjet head driving method, and an inkjet head driving program that uniformize the temperature distribution of a plurality of nozzles in an inkjet head using piezoelectric elements. .

The inkjet head driving device according to the present invention includes:
An inkjet head drive that forms an image by ejecting ink from the plurality of nozzles by driving the piezoelectric elements of each of the plurality of nozzles arranged along the width direction in the inkjet head by applying a drive pulse based on image data. A device,
a first generation unit that generates ejection pulse data having an ejection pulse waveform that drives the piezoelectric element to eject the ink from the image data;
With reference to the correspondence between the pixel value of the pixel of the image data or the ejection pulse waveform of the ejection pulse data and the temperature of the nozzle, find the temperature distribution of the plurality of nozzles in the width direction, and calculate the temperature. a second generation unit that calculates a complementary temperature distribution that complements the distribution of the temperature distribution, and generates dummy pulse data having a dummy pulse waveform for driving the piezoelectric element so as not to eject the ink from the complementary temperature distribution;
a third generation unit that generates the drive pulse based on composite pulse data obtained by combining the ejection pulse data and the dummy pulse data;
Equipped with.

The inkjet image forming apparatus according to the present invention includes:
An inkjet head that has a plurality of nozzles arranged along the width direction, and forms an image by ejecting ink from the plurality of nozzles by driving each piezoelectric element by applying a drive pulse based on image data. and,
the inkjet head driving device;
Equipped with

The method for driving an inkjet head according to the present invention includes:
An inkjet head that forms an image by ejecting ink from the plurality of nozzles by driving the piezoelectric elements of each of the plurality of nozzles arranged along the width direction of the inkjet head by applying a drive pulse based on image data. A driving method,
generating ejection pulse data having an ejection pulse waveform for driving the piezoelectric element to eject the ink from the image data;
With reference to the correspondence between the pixel value of the pixel of the image data or the ejection pulse waveform of the ejection pulse data and the temperature of the nozzle, find the temperature distribution of the plurality of nozzles in the width direction, and calculate the temperature. determining a complementary temperature distribution that complements the distribution of the ink, and generating dummy pulse data having a dummy pulse waveform for driving the piezoelectric element so as not to eject the ink from the complementary temperature distribution;
The driving pulse is generated based on composite pulse data obtained by combining the ejection pulse data and the dummy pulse data.

The inkjet head drive program according to the present invention includes:
An inkjet head that forms an image by ejecting ink from the plurality of nozzles by driving the piezoelectric elements of each of the plurality of nozzles arranged along the width direction of the inkjet head by applying a drive pulse based on image data. A driving program,
to the computer,
a process of generating ejection pulse data having an ejection pulse waveform for driving the piezoelectric element to eject the ink from the image data;
With reference to the correspondence between the pixel value of the pixel of the image data or the ejection pulse waveform of the ejection pulse data and the temperature of the nozzle, find the temperature distribution of the plurality of nozzles in the width direction, and calculate the temperature. determining a complementary temperature distribution that complements the distribution of the ink, and generating from the complementary temperature distribution dummy pulse data having a dummy pulse waveform for driving the piezoelectric element so as not to eject the ink;
a process of generating the drive pulse based on composite pulse data obtained by combining the ejection pulse data and the dummy pulse data;
Execute.

According to the present invention, it is possible to make the temperature distribution of a plurality of nozzles uniform in an inkjet head using piezoelectric elements.

1 is a diagram schematically showing an image forming apparatus according to an embodiment of the present invention. 2 is a block diagram showing main parts of a control system of the image forming apparatus shown in FIG. 1. FIG. FIG. 2 is a diagram showing an inkjet head installed in the image forming apparatus shown in FIG. 1, with a part thereof cut away. FIG. 3 is a diagram schematically illustrating a plurality of pressure chambers of an inkjet head, and is a diagram illustrating the pressure chambers when no drive pulse is applied. FIG. 3 is a diagram showing a pressure chamber of an inkjet head, and is a diagram showing the pressure chamber when a contraction pulse is applied as a drive pulse. FIG. 3 is a diagram showing a pressure chamber of an inkjet head, and is a diagram showing the pressure chamber when an expansion pulse is applied as a drive pulse. 4A to 4C are diagrams illustrating examples of a non-ejection waveform, an ejection pulse waveform, and a dummy pulse waveform. FIG. 1 is a block diagram illustrating an inkjet head driving device according to an embodiment of the present invention. 7 is a block diagram illustrating a procedure for generating ejection pulse data and dummy pulse data and synthesizing them to generate composite pulse data in the inkjet head driving device shown in FIG. 6. FIG. 8 is a diagram illustrating generation of the ejection pulse distribution pattern shown in FIG. 7. FIG. 8 is a diagram illustrating generation of the dummy pulse distribution pattern shown in FIG. 7. FIG. FIG. 7 is a diagram showing an example of combining ejection pulse data and dummy pulse data. FIG. 7 is a diagram showing another example of combining ejection pulse data and dummy pulse data. It is a block diagram explaining the inkjet head drive device of modification 1 of an embodiment of the present invention. 10 is a block diagram illustrating a procedure for generating dummy pulse data based on the temperature distribution and the heat generation amount distribution of a piezoelectric element in the inkjet head driving device shown in FIG. 9. 11 is a block diagram specifically explaining a part of the block diagram shown in FIG. 10. FIG. FIG. 7 is a diagram illustrating an upper limit value of the amount of heat generated based on the relationship between the amount of heat generated by the piezoelectric element and the amount of temperature rise of the nozzle as a second modification of the embodiment of the present invention. FIG. 7 is a diagram illustrating correction of complementary heat generation amounts in a plurality of inkjet heads arranged in a staggered manner as a third modification of the embodiment of the present invention.

Embodiments of the present invention will be described in detail below with reference to the drawings.

[Image forming device]
FIG. 1 is a diagram schematically showing an image forming apparatus 1 according to the present embodiment. FIG. 2 is a block diagram showing the main parts of the control system of the image forming apparatus 1. As shown in FIG.

The image forming apparatus 1 includes a paper feeding section 10, an image forming section 20, a paper discharging section 30, a control section 100 (see FIG. 2), and the like.

The image forming apparatus 1 transports the recording medium P stored in the paper feed section 10 to the image forming section 20 under the control of the control section 100, forms an image on the recording medium P in the image forming section 20, and then displays the image. The formed recording medium P is conveyed to the paper discharge section 30.

As the recording medium P, various media capable of fixing ink ejected from an inkjet head 90 described later can be used. The recording medium P is, for example, a sheet of paper, cloth, resin, or the like. Note that the recording medium P is not limited to a sheet-like medium, and may be a roll-like medium such as paper, cloth, or resin.

The paper feed section 10 includes a paper feed tray 11 that stores the recording medium P, and a medium supply section 12 that transports and supplies the recording medium P from the paper feed tray 11 to the image forming section 20. The medium supply unit 12 includes a ring-shaped belt whose inner side is supported by two rollers, and rotates the rollers with the recording medium P placed on this belt to feed the recording medium P from the paper feed tray 11. It is transported to the image forming section 20.

The image forming section 20 includes a transport section 21, a delivery section 22, a heating section 23, a fixing section 24, a delivery section 25, a head unit 50, and the like.

The conveying unit 21 holds the recording medium P placed on the conveying surface 212 (placing surface) of a cylindrical conveying drum 211, and the conveying drum 211 rotates in the direction of the arrow around its rotation axis (cylindrical axis). By rotating and moving around, a conveyance operation is performed to convey the recording medium P on the conveyance drum 211.

Note that here, as an example, the conveying unit 21 that conveys the recording medium P with the conveying drum 211 is illustrated, but the conveying unit 21 is not limited to the conveying drum 211, and the conveying unit 21 can convey the recording medium P with a conveying belt or a conveying roller. It may also be configured to be transported.

The delivery unit 22 delivers the recording medium P transported by the medium supply unit 12 of the paper feed unit 10 to the transport unit 21 . The delivery section 22 is provided at a position between the medium supply section 12 and the conveyance section 21 of the paper supply section 10, and picks up one end of the recording medium P conveyed from the medium supply section 12 by holding it with a swing arm section 221. , and delivered to the transport section 21 via the delivery drum 222.

The heating section 23 is provided between the arrangement position of the delivery drum 222 and the arrangement position of the head unit 50, and heats the recording medium P transported by the transport section 21 so that the temperature falls within a predetermined temperature range. Heat P. The heating unit 23 includes, for example, an infrared heater and the like, and energizes the infrared heater based on a control signal supplied from the control unit 100 to cause the infrared heater to generate heat.

The head unit 50 injects the recording medium P from nozzles provided on the ink ejection surface facing the conveyance surface 212 of the conveyance drum 211 at appropriate timing according to the rotation of the conveyance drum 211 holding the recording medium P. An image is formed by ejecting ink.

The head units 50 are positioned so that the ink ejection surface is separated by a predetermined distance from the transport surface 212. Here, four head units 50 corresponding to the four colors of ink, yellow (Y), magenta (M), cyan (C), and black (K), are arranged at predetermined intervals from the upstream side in the transport direction of the recording medium P in the order of Y, M, C, and K.

The fixing section 24 has a light emitting section arranged across the width of the conveyance section 21 (width in the rotation axis direction of the conveyance drum 211). The light emitting unit irradiates the recording medium P placed on the conveying unit 21 with energy rays such as infrared rays and ultraviolet rays to dry or harden the ink ejected onto the recording medium P and fix it. let The light emitting section of the fixing section 24 is arranged facing the transport surface 212 between the position of the head unit 50 and the position of the transfer drum 251 of the delivery section 25 in the transport direction.

The delivery section 25 includes a belt loop 252 having a ring-shaped belt whose inner side is supported by two rollers, and a cylindrical transfer drum 251 that transfers the recording medium P from the conveyance section 21 to the belt loop 252. The delivery unit 25 transports the recording medium P, which has been transferred from the transport unit 21 onto the belt loop 252 by the delivery drum 251, through the belt loop 252 and sends it out to the paper discharge unit 30.

The paper discharge section 30 has a plate-shaped paper discharge tray 31 on which the recording medium P sent out from the image forming section 20 by the delivery section 25 is placed.

As shown in FIG. 2, the image forming apparatus 1 includes a heating section 23, a fixing section 24, a head unit 50, a control section 100, a transport drive section 111, an operation display section 112, and an input/output interface 113 as main parts of the control system. Equipped with etc.

The control unit 100 includes a CPU (Central Processing Unit) 101, a RAM (Random Access Memory) 102, a ROM (Read Only Memory) 103, a storage unit 104, and the like.

The CPU 101 reads various control programs and setting data stored in the ROM 103, stores them in the RAM 102, and executes the programs to perform various calculation processes. Further, the CPU 101 centrally controls the entire operation of the image forming apparatus 1 .

The RAM 102 provides a working memory space for the CPU 101 and stores temporary data. Note that the RAM 102 may include nonvolatile memory.

The ROM 103 stores various control programs executed by the CPU 101, setting data, and the like. Note that in place of the ROM 103, a rewritable nonvolatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used.

The storage unit 104 stores a print job (image recording command) input from the external device 2 via the input/output interface 113 and image data related to the print job. As the storage unit 104, for example, a HDD (Hard Disk Drive) or an SSD (Solid State Drive) is used, and a DRAM (Dynamic Random Access Memory) or the like may also be used in combination.

The conveyance drive section 111 supplies a drive signal to the conveyance drum motor of the conveyance drum 211 based on the control signal supplied from the control section 100 . Thereby, the conveyance drive unit 111 rotates the conveyance drum 211 at a predetermined speed and timing. Further, the transport drive section 111 supplies drive signals to motors for operating the medium supply section 12 , the transfer section 22 , and the delivery section 25 based on the control signal supplied from the control section 100 . Thereby, the conveyance drive unit 111 supplies the recording medium P to the conveyance drum 211 and discharges it from the conveyance drum 211.

The operation display unit 112 is, for example, a flat panel display such as a liquid crystal display with a touch panel or an organic EL (Electro Luminescence) display. The operation display section 112 displays an operation menu for the user, information regarding image data, various states of the image forming apparatus 1, and the like. Further, the operation display section 112 includes a plurality of keys and receives various input operations from the user.

The input/output interface 113 mediates data transmission and reception between the external device 2 and the control unit 100. The input/output interface 113 is configured of, for example, one of various serial interfaces, various parallel interfaces, or a combination thereof.

The external device 2 is, for example, a personal computer, and supplies an image recording command (print job), image data, etc. to the control unit 100 via the input/output interface 113.

As described above, the heating unit 23 has an infrared heater and the like. Based on a control signal supplied from the control unit 100, the heating unit 23 energizes the infrared heater, causing it to generate heat and heat the recording medium P.

As described above, the fixing section 24 has a light emitting section. The fixing unit 24 causes a light emitting unit to emit light based on a control signal supplied from the control unit 100 and irradiates the recording medium P with energy rays such as infrared rays and ultraviolet rays, thereby fixing the ink ejected onto the recording medium P. Fix by drying or curing.

The head unit 50 includes a head drive section 51 (an inkjet head drive device in the present invention), an inkjet head (hereinafter referred to as a head) 90, and the like.

The head drive section 51 has a CPU, RAM, ROM, storage section, etc., substantially similar to the control section 100. The head drive unit 51 generates a drive pulse based on image data based on a control signal supplied from the control unit 100, and applies the drive pulse to the head 90 (piezoelectric element described later) at an appropriate timing. drive As a result, an image is formed by ejecting ink in an amount corresponding to the pixel value of the image data from the plurality of nozzles of the head 90.

Although not shown, the head unit 50 includes a sub-tank, a head 90, members related to ink supply (for example, a pump, a valve, etc.), and the like. Ink supplied from the main tank corresponding to each head unit 50 is stored in a sub-tank within the head unit 50. A plurality of heads 90 are connected to the sub-tank, and ink is supplied to these heads 90 from the sub-tank.

[Inkjet head]
The head 90 will be explained with reference to FIGS. 3 and 4A to 4C. FIG. 3 is a partially cutaway view showing the head 90. FIG. 4A is a diagram schematically showing the plurality of pressure chambers 92 of the head 90, and is a diagram showing the pressure chambers when no drive pulse is applied. FIG. 4B is a diagram showing the pressure chamber 92 of the head 90, and is a diagram showing the pressure chamber 92 when a contraction pulse is applied as a drive pulse. FIG. 4C is a diagram showing the pressure chamber 92 of the head 90, and is a diagram showing the pressure chamber 92 when an expansion pulse is applied as a drive pulse. Note that in FIGS. 4B and 4C, one pressure chamber 92 is illustrated for explanation.

As shown in Figures 3 and 4A, the head 90 has a number of nozzles 94 arranged along its width direction W. Specifically, the head 90 has a substrate 91 and a number of partitions 93 formed on the substrate 91 so as to separate grooves that become pressure chambers 92. The head 90 also has a nozzle plate 95 provided at one end of the longitudinal direction of the multiple pressure chambers 92, in which nozzles 94 corresponding to each pressure chamber 92 are formed, and a cover plate 96 provided to cover the multiple pressure chambers 92.

As shown in FIG. 3, one end of the pressure chamber 92 communicates with the outside via a nozzle 94, and the other end communicates with a common ink chamber 97. Although not shown, the common ink chamber 97 is covered by a cover member and connected to the sub-tank via a supply tube. The ink stored in the sub-tank is supplied to the common ink chamber 97 via the supply tube, and from the common ink chamber 97 to each pressure chamber 92.

Further, as shown in FIG. 3, the depth of the pressure chamber 92 in the depth direction D of the groove gradually becomes shallower from one end side (nozzle 94 side) to the other end side (common ink chamber 97 side). It is formed to be. A plurality of nozzles 94 are formed along the width direction W of the head 90, and the pressure chambers 92 are formed according to the number of nozzles 94.

The substrate 91 and the partition wall 93 are made of a piezoelectric material such as PZT (lead zirconate titanate). As shown in FIG. 4A, the partition wall 93 includes a first partition wall 93a and a second partition wall 93b that are arranged adjacent to each other in the depth direction D of the pressure chamber 92. The first partition wall 93a and the second partition wall 93b are formed from piezoelectric materials having mutually different polarization directions, and are bonded to each other at a bonding portion 93c (see FIGS. 4B and 4C). The first partition wall 93a and the second partition wall 93b of each partition wall 93 are provided with electrodes (not shown), and the electrodes are electrically connected to the wiring section 52, and the wiring section 52 is electrically connected to the head drive section 51. connected.

Therefore, a drive signal (drive pulse) from the head drive section 51 can be applied to the first partition wall 93a and the second partition wall 93b of each partition wall 93 via the wiring section 52. When a drive pulse is applied from the head drive unit 51 to the first partition wall 93a and the second partition wall 93b, the first partition wall 93a and the second partition wall 93b function as piezoelectric elements that shear and deform in response to the drive pulse.

The driving pulses applied to the first partition wall 93a and the second partition wall 93b are a contraction pulse consisting of a rectangular wave that contracts the volume of the pressure chamber 92 and then returns it to the original volume, and a contraction pulse that is made of a rectangular wave that returns the volume of the pressure chamber 92 to the original volume after expanding it. an expansion pulse consisting of a square wave that returns the volume to .

FIG. 4A is a diagram showing a case where a drive pulse is not applied from the head driving unit 51 to the first partition wall 93a and the second partition wall 93b in all the pressure chambers 92. In this case, the first partition wall 93a and the second partition wall The partition wall 93b does not deform, and the volume of the pressure chamber 92 does not change.

When applying a contraction pulse as a drive pulse to the first partition wall 93a and the second partition wall 93b, the head driving unit 51 applies the contraction pulse to the pair of first partition wall 93a and second partition wall 93b that constitute the pressure chamber 92. .

In this case, the joint portion 93c between the pair of first partition walls 93a and second partition walls 93b deforms toward the inside of the pressure chamber 92, and the volume of the pressure chamber 92 decreases, as shown in FIG. 4B.

On the other hand, when applying an expansion pulse as a drive pulse to the first partition wall 93a and the second partition wall 93b, the head driving unit 51 applies the expansion pulse to the pair of first partition wall 93a and second partition wall 93b that constitute the pressure chamber 92. Apply.

In this case, the joint portion 93c between the pair of first and second partition walls 93a and 93b deforms toward the outside of the pressure chamber 92, and the volume of the pressure chamber 92 increases, as shown in FIG. 4C.

After applying an expansion pulse to the ink in the pressure chamber 92, a contraction pulse is applied at a predetermined timing, causing the ink to be ejected from the nozzle 94. In this way, the combination of the expansion pulse and contraction pulse is a drive pulse for ejecting ink from the nozzle 94, and is hereafter referred to as an ejection pulse waveform.

On the other hand, when either the expansion pulse or the contraction pulse is applied to the pressure chamber 92, vibration (fluctuation) is applied to the ink within the pressure chamber 92, but the pressure necessary for ejection from the nozzle 94 is not applied. Ink is not ejected from the nozzle 94. Therefore, by applying either the expansion pulse or the contraction pulse to the pair of first partition walls 93a and second partition walls 93b, the pair of first partition walls 93a and second partition walls 93b generate heat without ejecting ink from the nozzle 94. can be done. The expansion pulse and the contraction pulse alone are drive pulses for raising the temperature without ejecting ink from the nozzle 94, and are hereinafter referred to as dummy pulse waveforms.

Generally, if the voltage change is dV, the amount of heat generated by the ejection pulse waveform or dummy pulse waveform Q can be expressed as Q∝dV ² . Therefore, the amount of heat generated Q has a correlation not with whether the pulse is an expansion pulse or a contraction pulse, but with the voltage change at that time. The dummy pulse waveform may be applied after the ejection pulse waveform is applied, but a pre-pulse method may be used in which the dummy pulse waveform is applied immediately before the ejection pulse waveform is applied. The pre-pulse method will be explained later in FIG. 8D.

Note that, hereinafter, the pair of first partition walls 93a and second partition walls 93b to which the above-described ejection pulse waveform and dummy pulse waveform are applied will be referred to as a piezoelectric element PE.

The head 90 having the above configuration is a so-called piezo type head. Therefore, there is a problem in that there is a difference in the amount of heat generated between the nozzles 94 that print (discharge ink) and the nozzles 94 that do not print, and a temperature difference occurs between the nozzles 94, resulting in fluctuations in print density.

In order to solve the problem, it is conceivable to apply a dummy drive pulse based on inverted data of the print data to the piezoelectric element in each nozzle 94, as well as a drive pulse based on the print data, similarly to the thermal type head.

However, the elements themselves are different between a thermal type head using a heating element and a piezo type head using a piezoelectric element, for example, the piezoelectric element is larger than the heating element. Therefore, in a piezo head, even if a dummy drive pulse based on inverted data is applied to each nozzle, it is difficult to bring each nozzle to a predetermined temperature, and it is difficult to make the temperature distribution of multiple nozzles uniform. That's difficult. Furthermore, the head itself has a large heat capacity, and there is a time lag between the heat generated by the piezoelectric element due to driving and the actual temperature distribution of the nozzle.

Therefore, in the present embodiment, a dummy pulse waveform (dummy pulse data) is generated by the procedure described below instead of a dummy pulse waveform based on inverted data. Then, the ejection pulse waveform (ejection pulse data) and the obtained dummy pulse waveform (dummy pulse data) are synthesized, and a drive pulse based on the synthesized combined pulse data is applied to the piezoelectric element PE, so that the plurality of nozzles 94 The temperature distribution is made uniform.

Here, we will first explain the ejection pulse waveform and the dummy pulse waveform with reference to Figure 5. Figure 5 is a diagram showing examples of a non-ejection waveform, an ejection pulse waveform, and a dummy pulse waveform.

FIG. 5 illustrates a waveform for one pixel period. Furthermore, in order to simplify the explanation that follows, the ejection pulse waveforms are exemplified by ejection pulse waveforms with a gradation value of 1 and a gradation value of 3. There are many waveform patterns depending on the dot diameter, etc. The same applies to the dummy pulse waveform, and dummy pulse waveforms with gradation values 2 and 4 are exemplified as dummy pulse waveforms, but the dummy pulse waveforms can be formed into a number of waveforms depending on the temperature to be compensated, etc. There's a pattern.

The non-ejection waveform and the ejection pulse waveform that constitute the ejection pulse data are generated based on the image data of the image formed by the head 90. Specifically, in the ejection pulse waveform, the dot diameter formed by the ejected ink is determined according to the pixel value of the pixel on the image data corresponding to one nozzle 94, and the dot of the determined dot diameter is determined. The ejection pulse waveform is generated so that

In the ejection pulse waveform forming one pixel, the number, pulse width, interval, etc. of expansion pulses and contraction pulses can be changed as appropriate depending on, for example, the dot diameter of the dots to be formed, and the dot diameter can be changed. This allows the print density to be changed.

Mainly, the amount of heat generated by the piezoelectric element PE changes depending on voltage changes in the ejection pulse waveform, etc., and the heat transfer to the adjacent nozzle 94 also changes. Therefore, through the process described later, a dummy pulse waveform is obtained that makes the temperature distribution of the plurality of nozzles 94 uniform, taking into account the influence of heat transfer from the surrounding nozzles 94.

In addition, in the ejection pulse waveform of gradation value 1 and gradation value 3, the peak voltage value of the expansion pulse and contraction pulse is fixed as an example, but the peak voltage value may vary depending on the size of the droplet etc. to be ejected. may be changed.

The non-ejection waveform and the dummy pulse waveform constituting the dummy pulse data are generated based on the image data of the image formed by the head 90 by the procedure shown in FIG. 7, which will be described later. Here, the dummy pulse waveforms of gradation value 2 and gradation value 4 shown in FIG. 5 are selected. When the head drive unit 51 selects the pre-pulse method described above, a dummy pulse waveform with a gradation value of 4 is selected. Furthermore, if temperature compensation is not required, a non-ejection waveform having a gradation value of 0 is selected. Such a dummy pulse waveform raises the temperature of the piezoelectric element PE corresponding to the nozzle 94 without ejecting ink from the nozzle 94.

In the dummy pulse waveform, the number, interval, etc. of expansion pulses (or contraction pulses) can be changed as appropriate depending on the temperature to be raised and the amount of heat generated. In addition, even in the dummy pulse waveforms of gradation value 2 and gradation value 4, the peak voltage value of the expansion pulse (or contraction pulse) is constant, but the peak voltage value is changed depending on the temperature to be raised and the amount of heat generated. You may. However, the number, interval, and peak voltage value of the expansion pulses (or contraction pulses) are set so as not to eject ink from the nozzle 94.

(Generation and synthesis of ejection pulse data and dummy pulse data)
A procedure including generation of dummy pulse data that can make the temperature distribution of the plurality of nozzles 94 uniform will be described with reference to FIGS. 6 to 8D.

FIG. 6 is a block diagram illustrating the head driving section 51. As shown in FIG. FIG. 7 is a block diagram illustrating a procedure for generating ejection pulse data and dummy pulse data and synthesizing them to generate composite pulse data in the head driving section 51. FIG. 8A is a diagram illustrating generation of the ejection pulse distribution pattern shown in FIG. 7. FIG. 8B is a diagram illustrating generation of the first dummy pulse distribution pattern shown in FIG. 7. FIG. 8C is a diagram illustrating an example of combining ejection pulse data and first dummy pulse data. FIG. 8D is a diagram showing another example of combining ejection pulse data and first dummy pulse data.

Regarding generation and synthesis of ejection pulse data and dummy pulse data, the head driving section 51 includes a first generation section B1, a second generation section B2, and a third generation section B3, as shown in FIGS. 6 and 7. Further, the second generation section B2 includes a first pattern generation section B211, a second pattern generation section B212, a third pattern generation section B213, and a fourth pattern generation section B214.

In the head drive section 51, the first generation section B1, the second generation section B2, and the third generation section B3 are configured of, for example, a digital arithmetic circuit having a DSP (Digital Signal Processor).

Note that a part or all of the first generation section B1, the second generation section B2, and the third generation section B3 may be configured from a dedicated hardware circuit (for example, ASIC or FPGA).

Further, the first generation unit B1, the second generation unit B2, and the third generation unit B3 may be partially or entirely configured from a program (a drive program that executes the drive method according to the present invention).

When the first generation unit B1, the second generation unit B2, and the third generation unit B3 are all configured from a program, the program may be executed by the control unit 100. In this case, the generation and synthesis of ejection pulse data and dummy pulse data are executed by the control section 100, and the generated combined pulse data is transmitted from the control section 100 to the head driving section 51.

The first generation section B1, second generation section B2 (first pattern generation section B211 to fourth pattern generation section B214), and third generation section B3 will be explained in detail below.

(First generation unit B1)
The first generation unit B1 generates ejection pulse data having an ejection pulse waveform that drives the piezoelectric element PE to eject ink from the nozzle 94, based on the image data of the image Im formed by the head 90.

Here, as an example, it is assumed that the head 90 has tens to hundreds of nozzles 94 arranged linearly along its width direction W (nozzle row direction). Note that instead of this, the head unit 50 has a plurality of heads 90 arranged linearly along its width direction W (nozzle row direction), and the head 90 has several tens to hundreds of nozzles 94. A configuration having the following may also be used.

As an example, assume that the image Im shown in FIGS. 7 and 8A is formed by the head 90. The image Im is formed across the nozzle row direction of the head 90 and the conveyance direction of the recording medium P (hereinafter simply referred to as the conveyance direction).

Then, for each nozzle 94 (piezoelectric element PE) of the head 90, ejection pulse data having an ejection pulse waveform is generated based on the image data (pixel values) of the image Im. FIG. 8A illustrates the no. 1 nozzle of the head 90, and ejection pulse data having an ejection pulse waveform corresponding to the pixel values is generated based on the pixel values of pixels P(1) to P(n) in the image data of the image Im corresponding to the no. 1 nozzle.

(Second generation unit B2)
The second generation unit B2 determines the distribution of the ejection pulse waveform in the nozzle row direction and the transport direction based on the ejection pulse data generated by the first generation unit B1.

In addition, the second generation unit B2 refers to the correspondence between the pixel value of the pixel in the image data of the image formed by the head 90 or the ejection pulse waveform of the ejection pulse data and the temperature of the nozzle 94, and determines the nozzle row direction and transport. Find the temperature distribution in the direction. Then, the second generation unit B2 obtains a complementary temperature distribution that complements the temperature distribution based on the temperature distribution.

Specifically, for a plurality of pixel values of pixels of image data, the correspondence relationship between the pixel value and the temperature of the nozzle 94 when an image of the pixel value is formed is obtained in advance, and the relationship is stored in the memory of the head drive unit 51, for example. It is stored as an LUT (Look Up Table) in the section. Then, the second generation unit B2 determines the temperature distribution in the width direction W of the head 90 based on the image data of the image formed by the head 90 and the LUT.

Note that instead of the pixel value of the pixel, the correspondence relationship between the ejection pulse waveform corresponding to the pixel value and the temperature of the nozzle 94 when an image is formed with the ejection pulse waveform is obtained in advance, and for example, It may be stored in the storage unit as an LUT. In this case, the second generation unit B2 determines the temperature distribution in the width direction W of the head 90 based on the ejection pulse waveform generated by the first generation unit B1 and the LUT.

Then, based on the temperature distribution obtained in this way, the second generation unit B2 obtains a complementary temperature distribution that complements the temperature distribution, and from the complementary temperature distribution, the piezoelectric element PE is set so as to prevent ink from being ejected. Dummy pulse data having a dummy pulse waveform to be driven is generated.

Specifically, the second generation section B2 generates a dummy pulse distribution pattern to be used as dummy pulse data via a first pattern generation section B211 to a third pattern generation section B214, which will be described below.

(First pattern generation unit B211)
The first pattern generation section B211 generates an ejection pulse distribution pattern indicating a distribution of ejection pulse waveforms based on the ejection pulse data generated by the first generation section B1. The first pattern generation section B211 generates an ejection pulse distribution pattern to be used as ejection pulse data in the third generation section B3.

The first pattern generation unit B211 generates an ejection pulse distribution pattern indicating the distribution of ejection pulse waveforms based on the relationship between the gradation values and waveforms shown in FIG. 5, for example. To simplify the explanation, for example, using the non-ejection waveform with a gradation value of 0 and the ejection pulse waveform with a gradation value of 1 shown in FIG. When an ejection pulse distribution pattern is generated from ejection pulse data of one nozzle, an ejection pulse distribution pattern as shown in FIG. 8A is generated. And for all nozzles, no. Similarly to one nozzle, an ejection pulse distribution pattern is generated.

In the areas corresponding to each pixel in the ejection pulse distribution pattern of nozzle no. 1 and head 90, a gradation value of 0 is indicated by a blank space, and a gradation value of 1 is indicated by a diagonal line pattern slanting downward to the left. In addition, the ejection pulse distribution pattern of head 90 illustrates a portion of the ejection pulse distribution pattern in the nozzle row direction and the transport direction.

In the ejection pulse distribution pattern generated by the first pattern generation unit B211, the axis in the nozzle row direction is an axis representing the position in the width direction W of the head 90, the axis in the transport direction is the time axis of the ejection pulse data, and 2 It is a pattern that has dimensional information. In other words, the ejection pulse distribution pattern indicates a distribution of ejection pulse waveforms over time in the width direction W of the head 90.

(Second pattern generation unit B212)
The second pattern generation unit B212 determines the correspondence relationship between the pixel value of a pixel in the image data of the image formed by the head 90 or the ejection pulse waveform of the ejection pulse data and the temperature of the nozzle 94, for example, with reference to the above-mentioned LUT, and generates a nozzle. Obtain the temperature distribution in the row direction and conveyance direction. Then, the second pattern generation unit B212 generates a temperature distribution pattern representing the temperature distribution based on the temperature distribution. The second pattern generation unit B212 generates a temperature distribution pattern, for example, as an image pattern expressing such temperature distribution using shading.

In the temperature distribution pattern generated by the second pattern generation unit B212, the axis in the nozzle row direction is an axis representing the position in the width direction W of the head 90, and the axis in the transport direction is the time axis, similarly to the ejection pulse distribution pattern. This is a pattern having two-dimensional information. In other words, the temperature distribution pattern indicates a temperature distribution over time in the width direction W of the head 90. Based on such a temperature distribution pattern, a complementary temperature distribution pattern is generated as described below, so the dummy pulse distribution pattern is generated in response to temperature changes in the width direction W and temporal temperature changes. That will happen.

(Third pattern generation unit B213)
The third pattern generation unit B213 generates a complementary temperature distribution pattern indicating a complementary temperature distribution that complements the temperature distribution of the temperature distribution pattern, based on the temperature distribution of the temperature distribution pattern generated by the second pattern generation unit B212. generate. The third pattern generation unit B213 generates a complementary temperature distribution pattern, for example, as an image pattern expressing such complementary temperature distribution using shading.

"Complementary" refers to a relationship that complements each other, and here, when a temperature distribution pattern and a complementary temperature distribution pattern are combined, a complementary temperature distribution pattern is generated that has a uniform temperature distribution. do.

(Fourth pattern generation unit B214)
The fourth pattern generation unit B214 generates a first dummy pulse waveform that indicates a distribution of a dummy pulse waveform in which a complementary amount of heat generation occurs in the piezoelectric element PE, based on the complementary temperature distribution of the complementary temperature distribution pattern generated by the third pattern generation unit B213. Generate a pulse distribution pattern. The fourth pattern generation section B214 generates a first dummy pulse distribution pattern to be used as dummy pulse data in the third generation section B3.

As described above, the amount of heat generated by the piezoelectric element PE can be calculated based on the voltage change in the dummy pulse waveform. For example, in the dummy pulse waveform of gradation value 2 shown in FIG. 5, the amount of heat generated is calculated in advance based on the voltage change and the like. Then, the fourth pattern generation unit B214 obtains a dummy pulse waveform corresponding to the complementary temperature (heat amount) based on the complementary temperature distribution of the complementary temperature distribution pattern that correlates with the complementary heat amount. Then, the fourth pattern generation unit B214 generates a first dummy pulse distribution pattern indicating the distribution of the dummy pulse waveform in the head 90 based on the obtained dummy pulse waveform.

The fourth pattern generating unit B214 generates a dummy pulse distribution pattern that indicates the distribution of a dummy pulse waveform, for example, based on the relationship between the gradation value and the waveform shown in FIG. 5. For ease of explanation, for example, when a dummy pulse distribution pattern is generated from a complementary temperature distribution pattern using the non-ejection waveform of gradation value 0 and the dummy pulse waveform of gradation value 2 shown in FIG. 5, a dummy pulse distribution pattern as shown in FIG. 8B is generated. Note that in the areas corresponding to each pixel in the dummy pulse distribution pattern, gradation value 0 is indicated by a blank, and gradation value 3 is indicated by a diagonal line pattern slanting downward to the right. The dummy pulse distribution pattern also illustrates a portion of the dummy pulse distribution pattern in the nozzle row direction and the transport direction of the head 90.

(Third generation unit B3)
The third generation unit B3 combines the ejection pulse data and the dummy pulse data to generate composite pulse data, and generates a drive pulse based on the composite pulse data.

Specifically, the third generation unit B3 uses the ejection pulse distribution pattern generated by the first pattern generation unit B211 as the ejection pulse data, and uses the ejection pulse distribution pattern generated by the fourth pattern generation unit B214 as the dummy pulse data. 1 dummy pulse distribution pattern is used. The third generation unit B3 then combines the ejection pulse distribution pattern and the first dummy pulse distribution pattern to generate a composite pattern, generates composite pulse data based on the composite pattern, and generates composite pulse data based on the composite pulse data. Generate drive pulses. That is, the third generation unit B3 generates composite pulse data including ejection pulse data having an ejection pulse waveform and first dummy pulse data having a dummy pulse waveform, and based on the composite pulse data including such data. Generate drive pulses.

During pattern synthesis, the third generation unit B3 preferentially selects the ejection pulse distribution pattern and synthesizes the ejection pulse distribution pattern and the first dummy pulse distribution pattern, for example, as shown in FIG. 8C. , generate a composite pattern. In addition, in the area corresponding to each pixel in the pattern shown in FIG. 8C, with reference to FIG. Indicated by a diagonal pattern. Moreover, each pattern shown in FIG. 8C illustrates a part of the pattern in the nozzle row direction and the conveyance direction.

Then, the third generation unit B3 generates composite pulse data including ejection pulse data having an ejection pulse waveform and dummy pulse data having a dummy pulse waveform from the synthesized composite pattern based on the relationship between the gradation value and the waveform shown in Figure 5.

For example, in FIG. 8C, head 90 no. 1 nozzle is illustrated, and no. From the composite pattern corresponding to one nozzle, no. Synthetic pulse data for pixels P(1) to P(n) in one nozzle is generated. Similarly, synthetic pulse data is generated for other nozzles of the head 90 from the corresponding synthetic patterns.

Note that here, the third generation unit B3 preferentially selects the ejection pulse distribution pattern during pattern synthesis, but instead of this, the fourth pattern generation unit B214 selects the ejection pulse distribution pattern with priority. Alternatively, an exclusive dummy pulse distribution pattern may be generated. Specifically, the fourth pattern generation unit B214 generates a dummy pulse distribution pattern exclusively for the ejection pulse distribution pattern so that both the ejection pulse waveform and the dummy pulse waveform do not have the same nozzle and the same timing. Do it like this. Even in this case, the composite pattern shown in FIG. 8C can be generated.

Further, when both the ejection pulse waveform and the dummy pulse waveform are for the same nozzle and the same timing, the third generation unit B3 synthesizes the ejection pulse waveform and the dummy pulse waveform within one pixel period. Good too.

For example, as shown in FIG. 8D, when the third generation unit B3 synthesizes the ejection pulse distribution pattern and the dummy pulse distribution pattern, the part corresponding to the ejection pulse waveform and the part corresponding to the dummy pulse waveform may overlap. In FIG. 8D, the area where the area corresponding to the ejection pulse waveform and the area corresponding to the dummy pulse waveform overlap (the area corresponding to a pixel) is shown by a diagonal cross line pattern.

In such a case, the third generation unit B3 uses the ejection pulse waveform of gradation value 3 and the dummy pulse waveform of gradation value 4 shown in FIG. A composite pulse waveform may be generated by combining the ejection pulse waveform and the dummy pulse waveform.

If either the ejection pulse waveform or the dummy pulse waveform is selected for the piezoelectric element PE, excessive heat may be applied to the piezoelectric element PE. In such a case, the third generation unit B3 generates a composite pulse waveform as shown in FIG. 8D to prevent excessive heat from being applied to the piezoelectric element PE and prevent deterioration of the head 90 itself due to heat. It can be prevented.

The head drive unit 51 applies the drive pulse generated by the above procedure to each piezoelectric element PE of the plurality of nozzles 94 in the head 90. By applying the drive pulse generated in this way to the piezoelectric element PE, a desired image can be formed and the temperature distribution of the plurality of nozzles 94 can be made uniform.

As described above, in this embodiment, the head drive unit 51 includes a first generation unit B1, a second generation unit B2, and a third generation unit B3. The first generation unit B1 generates ejection pulse data for driving each piezoelectric element PE to eject ink from the multiple nozzles 94 based on image data of an image formed by the head 90. The second generation unit B2 obtains a temperature distribution in the nozzle row direction and the transport direction, a complementary temperature distribution, by referring to the correspondence between the image data or the ejection pulse data and the nozzle temperature. Then, the second generation unit B2 generates dummy pulse data for raising the temperature of the piezoelectric element PE without ejecting ink from the complementary temperature distribution. The third generation unit B3 generates a drive pulse for driving the piezoelectric element PE based on composite pulse data obtained by combining the ejection pulse data and the dummy pulse data.

According to this embodiment configured in this way, dummy pulse data is generated based on a complementary temperature distribution that complements the temperature distribution in the nozzle row direction and the transport direction. The drive pulse generated using such dummy pulse data raises the temperature in the nozzle row direction, that is, in the width direction W of the head 90 so as to have a uniform temperature distribution. Further, the drive pulse generated in this manner increases the temperature so that a uniform temperature distribution is achieved in the transport direction, that is, also on the time axis. Since the head 90 is driven using such a drive pulse, a desired image can be formed and the temperature distribution of the plurality of nozzles 94 can be made uniform. Further, temporal changes in temperature of the plurality of nozzles 94 can also be made uniform.

Since the temperature distribution of the plurality of nozzles 94 is made uniform, it is possible to suppress variations in print density due to temperature distribution, and it is possible to improve the quality of the formed image. In addition, it is possible to increase the temperature of the head 90 to an appropriate temperature to suppress excessive temperature rise, and it is possible to extend the life of the head 90.

Note that in this embodiment, it is more desirable to obtain the ejection pulse data by performing the following processing.

(Processing P1)
The fourth pattern generation unit B214 described above quantizes the complementary temperature distribution of the complementary temperature distribution pattern generated by the third pattern generation unit B213, and indicates the distribution of the dummy pulse waveform in which the complementary amount of heat generation occurs in the piezoelectric element PE. A first dummy pulse distribution pattern may be generated. At this time, the error diffusion method or dither method is used for quantization.

By quantizing the complementary temperature distribution of the complementary temperature distribution pattern, it is possible to easily generate a first dummy pulse distribution pattern that can generate dummy pulse data.

Further, an error diffusion method or a dither method is used for quantizing the complementary temperature distribution of the complementary temperature distribution pattern. As a result, for the target nozzle 94, a distribution of dummy pulse waveforms is generated by taking into consideration the temporal change in its complementary temperature and the complementary temperature (including the temporal change) of the adjacent nozzle 94. In this way, by generating the first dummy pulse distribution pattern which is the distribution of dummy pulse waveforms by all the nozzles 94, the first dummy pulse is generated in consideration of the temporal change in complementary temperature and the complementary temperature of adjacent nozzles 94. This will generate a distribution pattern.

Then, by generating dummy pulse data based on the first dummy pulse distribution pattern generated in this way, dummy pulse data is generated that takes into account temporal changes in complementary temperature and the influence of complementary temperatures of adjacent nozzles 94. will be generated. As a result, the temperature distribution of the plurality of nozzles 94 can be made more uniform, and the temporal change in temperature of the plurality of nozzles 94 can also be made more uniform.

<Modification 1>
In the embodiment described above, the second generation unit B2 obtains the temperature distribution of the plurality of nozzles 94, obtains a complementary temperature distribution that complements the temperature distribution, and generates dummy pulse data from the complementary temperature distribution. . In addition to this, dummy pulse data may be generated taking into account the amount of heat generated by the piezoelectric element PE.

Here, FIG. 9 is a block diagram illustrating the head drive section 51 of this modification. FIG. 10 is a block diagram illustrating a procedure for generating dummy pulse data based on the temperature distribution and the heat generation distribution of the piezoelectric element PE in the head driving section 51 of this modification. FIG. 11 is a block diagram specifically explaining a part of the block diagram shown in FIG. 10. Note that in FIGS. 9 to 11, the same reference numerals are given to the configurations explained in FIGS. 6 and 7, and redundant explanations will be omitted.

(First generation unit B1)
The first generation unit B1 is as described in FIG. 7.

(Second generation unit B2)
The second generation section B2 includes a sub-pattern generation section B22 and a synthesis section B224, and executes the following procedure in addition to the procedure explained in FIG. 7.

The sub-pattern generation unit B22 determines the distribution of the ejection pulse waveform in the nozzle row direction and the transport direction based on the ejection pulse data generated by the first generation unit B1. Then, based on the distribution of the ejection pulse waveform, the distribution of the amount of heat generated by the piezoelectric element PE due to the ejection pulse waveform is determined, and a complementary distribution of the amount of heat generated that complements the distribution of the amount of heat generated is determined. Then, from the complementary heat generation amount distribution, a second dummy pulse distribution pattern indicating a distribution of a dummy pulse waveform that raises the temperature of the piezoelectric element PE without ejecting ink is generated.

Specifically, the sub-pattern generation unit B22 generates the second dummy pulse distribution pattern via the fifth pattern generation unit B221 to the seventh pattern generation unit B223 described below.

(Fifth pattern generation unit B221)
The fifth pattern generation section B221 generates a heat generation distribution pattern indicating the distribution of the heat generation amount of the head 90 based on the ejection pulse distribution pattern generated by the first pattern generation section B211.

As described above, the amount of heat generated by the piezoelectric element PE can be calculated based on the voltage change in the ejection pulse waveform. For example, in the ejection pulse waveform of gradation value 1 shown in FIG. 5, the amount of heat generated is calculated in advance based on the voltage change and the like. Then, the fifth pattern generation unit B221 calculates the amount of heat generated based on the ejection pulse waveform of the ejection pulse distribution pattern, and generates a heat amount distribution pattern indicating the distribution of the amount of heat generated by the head 90. The fifth pattern generation unit B221 generates a calorific value distribution pattern as an image pattern representing such a distribution of calorific value in shading, for example.

(Sixth pattern generation unit B222)
The sixth pattern generating unit B222 indicates a complementary calorific value distribution that complements the calorific value distribution of the calorific value distribution pattern based on the calorific value distribution of the calorific value distribution pattern generated by the fifth pattern generating unit B221. Generate complementary calorific value distribution patterns. The sixth pattern generation unit B222 generates a complementary calorific value distribution pattern, for example, as an image pattern expressing such a complementary calorific value distribution in shading.

"Complementary" means to be in a relationship that complements each other. Generate distribution patterns.

(Seventh pattern generation unit B223)
The seventh pattern generation unit B223 generates a pattern indicating the distribution of the dummy pulse waveform in which the complementary heat generation amount is generated in the piezoelectric element PE, based on the complementary heat generation amount distribution of the complementary heat generation amount distribution pattern generated by the sixth pattern generation unit B222. 2. Generate a dummy pulse distribution pattern. The seventh pattern generation section B223 is configured to generate a second dummy pulse distribution pattern to be used as dummy pulse data by combining it with the first dummy pulse distribution pattern in the third generation section B3.

As described above, the amount of heat generated by the piezoelectric element PE can be calculated based on the voltage change in the dummy pulse waveform. For example, in the dummy pulse waveform of gradation value 2 shown in FIG. 5, the amount of heat generated is calculated in advance based on the voltage change and the like. Then, the seventh pattern generation unit B223 calculates a dummy pulse waveform corresponding to the complementary heat generation amount based on the complementary heat generation amount distribution of the complementary heat generation amount distribution pattern that correlates with the complementary heat generation amount, and generates a dummy pulse waveform in the head 90. A second dummy pulse distribution pattern showing the distribution of is generated.

The seventh pattern generation unit B223 generates a second dummy pulse distribution pattern indicating the distribution of dummy pulse waveforms, based on the relationship between the gradation values and the waveforms shown in FIG. 5, for example. For example, as explained with reference to FIG. 8B, the second dummy pulse distribution pattern is derived from the complementary heat generation amount distribution pattern using the non-ejection waveform with the gradation value 0 and the dummy pulse waveform with the gradation value 2 shown in FIG. Suppose we generate it. In this case, a second dummy pulse distribution pattern similar to the first dummy pulse distribution pattern shown in FIG. 8B will be generated.

The ejection pulse distribution pattern generated by the first pattern generation unit B211 indicates the distribution of ejection pulse waveforms in the nozzle row direction and the transport direction. Since the above-mentioned calorific value distribution pattern and complementary calorific value distribution pattern are generated based on such an ejection pulse distribution pattern, the second dummy pulse distribution pattern is generated based on the temperature change in the width direction W and the temporal temperature change. will be generated accordingly.

(Composition section B224)
The combining unit B224 generates a dummy pulse distribution pattern by combining the first dummy pulse distribution pattern generated by the fourth pattern generating unit B214 and the second dummy pulse distribution pattern generated by the seventh pattern generating unit B223. . The combining unit B224 generates a dummy pulse distribution pattern by combining the first dummy pulse distribution pattern and the second dummy pulse distribution pattern, for example, in a ratio of 50:50.

(Third generation unit B3)
The third generation unit B3 is basically as explained in FIG. 7, but as dummy pulse data, the dummy pulse distribution pattern (first dummy pulse distribution pattern and second pulse distribution pattern) is used. Then, the third generation unit B3 generates a composite pattern by combining the ejection pulse distribution pattern and the dummy pulse distribution pattern, generates composite pulse data based on the composite pattern, and generates drive pulses based on the composite pulse data. generate. That is, the third generation unit B3 generates composite pulse data including ejection pulse data having an ejection pulse waveform and dummy pulse data having a dummy pulse waveform, and generates drive pulses based on the composite pulse data including such data. generate.

The head driver 51 applies the drive pulses generated by the above procedure to the piezoelectric elements PE of each of the multiple nozzles 94 in the head 90. By applying the drive pulses generated in this manner to the piezoelectric elements PE, it is possible to form a desired image and to make the temperature distribution of the multiple nozzles 94 uniform.

As explained above, in this displacement example, the second generating section B2 of the head driving section 51 further includes a sub-pattern generating section B22 and a combining section B224. The sub-pattern generation unit B22 obtains a heat generation amount distribution and a complementary heat generation amount distribution corresponding to the distribution of the ejection pulse waveform of the ejection pulse data in the nozzle row direction and the transport direction. Then, the sub-pattern generation unit B22 generates a second dummy pulse distribution pattern that raises the temperature of the piezoelectric element PE without ejecting ink from the complementary heat generation amount distribution. The synthesizing unit B224 synthesizes the first dummy pulse distribution pattern and the second dummy pulse distribution pattern to generate a dummy pulse distribution pattern.

According to this displacement example configured in this way, dummy pulse data is generated based on the complementary temperature distribution and complementary heat generation amount distribution that complement the distribution of temperature and heat generation amount in the nozzle row direction and the conveyance direction. The drive pulse generated using such dummy pulse data raises the temperature in the nozzle row direction, that is, in the width direction W of the head 90 so as to have a uniform temperature distribution. Further, the drive pulse generated in this manner increases the temperature so that a uniform temperature distribution is achieved in the transport direction, that is, also on the time axis. Since the head 90 is driven using such a drive pulse, a desired image can be formed and the temperature distribution of the plurality of nozzles 94 can be made uniform. Further, temporal changes in temperature of the plurality of nozzles 94 can also be made uniform.

Since the temperature distribution of the plurality of nozzles 94 is made uniform, the same effects as in the above embodiment can be achieved.

Note that in this modification, it is more desirable to obtain the ejection pulse data by performing the following processing.

(Processing P2)
The fifth pattern generation unit B221 described above may generate the calorific value distribution pattern by applying a low-pass filter to the distribution of the ejection pulse waveform in the ejection pulse distribution pattern generated by the first pattern generation unit B211. .

Specifically, the fifth pattern generation unit B221 converts the pulse widths of the expansion pulses and contraction pulses of each ejection pulse waveform distributed in the ejection pulse distribution pattern into frequencies. Then, a low-pass filter is applied to the converted frequencies to generate a heat generation amount distribution pattern based on the expansion pulses and contraction pulses of relatively low frequencies. Since expansion pulses and contraction pulses with large pulse widths have low frequencies and expansion pulses and contraction pulses with small pulse widths have high frequencies, the low-pass filter is used to remove the expansion pulses and contraction pulses with small pulse widths to generate a heat generation amount distribution pattern.

Then, by generating a complementary calorific value distribution pattern and a second dummy pulse distribution pattern based on the calorific value distribution pattern generated in this way, ejection pulse data that can raise the temperature to an appropriate temperature can be generated. Become. As a result, the temperature of the plurality of nozzles 94 can be increased to an appropriate temperature, and the temperature distribution can be made more uniform.

(Processing P3)
The fifth pattern generation unit B221 described above may generate the calorific value distribution pattern by applying a spatial filter to the distribution of the ejection pulse waveform in the ejection pulse distribution pattern generated by the first pattern generation unit B211. .

The fifth pattern generation unit B221 generates a calorific value distribution pattern by applying a spatial filter to the distribution of the ejection pulse waveform. As a result, the amount of heat generated from the target nozzle 94 is determined by taking into account the change in the ejection pulse waveform of the target nozzle 94 in the transport direction and the ejection pulse waveform of the adjacent nozzle 94 (including the change in the transport direction). In this way, by generating a calorific value distribution pattern that is a distribution of calorific value by all nozzles 94, changes in the ejection pulse waveform of each nozzle 94 in the transport direction and the ejection pulse waveform of adjacent nozzles 94 are taken into account. This will generate a calorific value distribution pattern.

Then, a complementary calorific value distribution pattern and a second dummy pulse distribution pattern are generated based on the calorific value distribution pattern generated in this way. As a result, ejection pulse data is generated that takes into account the influence of temporal changes in the amount of heat generated by each nozzle 94 and the amount of heat generated from adjacent nozzles 94 (including changes in the amount of heat generated over time). As a result, the temperature distribution of the plurality of nozzles 94 can be made more uniform.

Note that here, a spatial filter is applied to the distribution of the ejection pulse waveform, but after the calorific value distribution pattern is generated based on the distribution of the ejected pulse waveform, the spatial filter is applied to the calorific value distribution pattern. Alternatively, the final calorific value distribution pattern may be generated.

(Processing P4)
The sixth pattern generating unit B222 described above may generate a complementary calorific value distribution pattern by applying a spatial filter to the calorific value distribution of the calorific value distribution pattern generated by the fifth pattern generating unit B221. .

The sixth pattern generation unit B222 applies a spatial filter to the distribution of the calorific value of the calorific value distribution pattern to generate a complementary calorific value distribution pattern. As a result, the complementary amount of heat generated by the target nozzle 94 is determined by taking into consideration the temporal change in the amount of heat generated by the target nozzle 94 and the amount of heat generated by adjacent nozzles 94 (including the change in time). In this way, by generating a complementary calorific value distribution pattern consisting of a complementary calorific value distribution that complements the calorific value distribution of all the nozzles 94, temporal changes in the calorific value of each nozzle 94 and changes in the calorific value of adjacent nozzles 94 can be A complementary calorific value distribution pattern is generated in consideration of the calorific value.

Then, a second dummy pulse distribution pattern is generated based on the complementary heat generation amount distribution pattern generated in this way. As a result, ejection pulse data is generated that takes into account temporal changes in the amount of heat generated by each nozzle 94 and the influence of the amount of heat generated by adjacent nozzles 94. As a result, the temperature distribution of the plurality of nozzles 94 can be made more uniform.

(Processing P5)
The seventh pattern generation section B223 described above quantizes the complementary heat generation amount distribution of the complementary heat generation amount distribution pattern generated by the sixth pattern generation section B222, and generates a distribution of dummy pulse waveforms in which complementary heat generation amounts are generated in the piezoelectric element PE. A second dummy pulse distribution pattern may be generated. At this time, the error diffusion method or dither method is used for quantization.

By quantizing the complementary calorific value distribution of the complementary calorific value distribution pattern, it is possible to easily generate a second dummy pulse distribution pattern that can generate dummy pulse data.

Further, the seventh pattern generation unit B223 uses an error diffusion method or a dither method to quantize the complementary heat generation amount distribution pattern. As a result, a distribution of dummy pulse waveforms can be generated for the target nozzle 94 by taking into consideration the temporal change in its complementary heat generation amount and the complementary heat generation amount (including the temporal change) of adjacent nozzles 94. Become. In this way, a second dummy pulse distribution pattern, which is a distribution of dummy pulse waveforms from all the nozzles 94, is generated. As a result, a second dummy pulse distribution pattern is generated that takes into account temporal changes in the complementary heat generation amount of each nozzle 94 and the complementary heat generation amount of adjacent nozzles 94.

Then, dummy pulse data is generated based on the second dummy pulse distribution pattern generated in this way. As a result, dummy pulse data is generated that takes into consideration temporal changes in the complementary heat generation amount of each nozzle 94 and the influence of the complementary heat generation amount of adjacent nozzles 94. As a result, the temperature distribution of the plurality of nozzles 94 can be made more uniform.

<Modification 2>
In the embodiment described above, the sixth pattern generation unit B222 generates the complementary heat generation distribution pattern based on the heat generation distribution pattern, but the heat generation amount of the piezoelectric element PE and the amount of temperature rise of the nozzle 94 are in a proportional relationship. There may be cases where it is not available. In such a case, it is desirable to generate a complementary calorific value distribution pattern in consideration of the relationship between the calorific value of the piezoelectric element PE and the amount of temperature rise of the nozzle 94.

Here, FIG. 12 is a diagram illustrating the upper limit value of the calorific value defined based on the relationship between the calorific value of the piezoelectric element PE and the amount of temperature rise of the nozzle 94. FIG. 12 shows, as an example, the amount of heat generated by the piezoelectric element PE and the amount of temperature rise of the nozzle 94 in each area when the printing pattern is such that the printing density is increased for each area in the nozzle row direction (width direction W in FIG. 4A). It shows a relationship. For convenience of explanation, in the nozzle row direction, the no. 1~no. Area number 8 is attached. Area number no. 1~no. Each of the 8 areas has the same number of nozzles 94 (for example, several tens of nozzles 94).

When the amount of heat generated by the piezoelectric element PE and the amount of temperature rise of the nozzle 94 are in a proportional relationship, as explained in the above embodiment, if a complementary heat amount distribution pattern is generated based on the heat amount distribution pattern, a plurality of It is possible to generate dummy pulse data that makes the temperature distribution of the nozzle 94 uniform.

On the other hand, if the amount of heat generated by the piezoelectric element PE and the amount of temperature rise in the nozzle 94 are not in a proportional relationship, a complementary heat amount distribution pattern is generated by considering the relationship between the amount of heat generated in the piezoelectric element PE and the amount of temperature rise in the nozzle 94. Otherwise, the temperature may rise excessively due to the generated dummy pulse data.

For example, as shown in FIG. 12, when the amount of heat generation of the piezoelectric element PE increases and the amount of temperature increase of the nozzle 94 becomes saturated, in the above embodiment, for example, in the area number no. A complementary calorific value distribution pattern is generated based on the maximum calorific value of No. 8. In this case, area number no. 6, no. 7, area number no. 8 and the amount of temperature rise is the same, but there is a difference in the amount of heat generated, so a complementary amount of heat is generated. Therefore, there is a possibility that the temperature rise will be excessive in the dummy pulse data generated based on the generated complementary heat generation amount.

Therefore, in this modification, a reference calorific value (upper limit value of calorific value shown in FIG. 12) is determined from the viewpoint of the amount of temperature rise, and a complementary calorific value distribution pattern is generated based on the calorific value. .

For example, in the example shown in FIG. 12, area number no. 6 has the maximum temperature increase, so area number no. The calorific value of 6 is defined as the upper limit value of calorific value, and a complementary calorific value distribution pattern is generated based on the upper limit value of calorific value. In this case, area number no. 1~no. In step 5, a complementary calorific value distribution pattern is generated by using the difference between these calorific values and the calorific value upper limit value as a complementary calorific value. On the other hand, area number no. 6~no. In case No. 8, since their calorific values are greater than the upper limit value of calorific value, no complementary calorific value is generated.

As explained above, in this modification, the sixth pattern generation unit B222 has an upper limit value of the heat value of the heat value generated by the piezoelectric element PE, and generates a complementary heat value distribution pattern so as not to exceed the upper limit value of the heat value. generate.

According to this modified example configured in this manner, the complementary heat generation amount distribution pattern is generated based on the upper heat generation amount limit value, so the dummy pulse data generated based on the complementary heat generation amount distribution pattern does not cause excessive temperature rise. Therefore, while achieving the same effects as the above embodiment, it is possible to further suppress excessive heat generation of the head 90, thereby further extending the life of the head 90.

<Modification 3>
In the above-mentioned embodiment and modifications 1 and 2, a configuration including a plurality of heads 90 arranged in a straight line along the width direction W was described, but the head unit 50 is arranged in a straight line along the width direction W. In some cases, the configuration includes a plurality of heads 90 arranged in a staggered manner. In this modification, a case will be described in which a plurality of heads 90 are arranged in this manner.

FIG. 13 is a diagram illustrating correction of complementary heat generation amounts in a plurality of heads 90-1 and 90-2 arranged in a staggered manner. Note that FIG. 13 shows two heads 90-1 and 90-2 arranged in a staggered manner as the simplest example of a plurality of heads arranged in a staggered manner.

As shown in FIG. 13, the heads 90-1 and 90-2 are arranged in a staggered manner along the width direction W so that the positions of some nozzles overlap with each other in the width direction W. Here, as an example, the head 90-1 no. 8 nozzle and head 90-2 no. The heads 90-1 and 90-2 are arranged so that the positions of one nozzle overlap each other in the width direction W.

Further, as an example, heads 90-1 and 90-2 are driven to form an image Im shown in FIG. 13. Based on the image data of the image Im shown in FIG. 13, the composite pulse data (ejection pulse data, dummy pulse data) etc. described in the above embodiment are generated, and in the process, the graph shown in the graph before correction in FIG. A complementary calorific value (complementary calorific value pattern) is generated.

By using the dummy pulse data that generates the complementary heat generation amount generated in this way, it is possible to make the temperature distribution of the plurality of nozzles 94 uniform in each of the heads 90-1 and 90-2.

However, there is a space between the two heads 90-1 and 90-2, and they are thermally independent of each other. Therefore, a temperature difference may occur between the two heads 90-1 and 90-2.

For example, the head 90-2 forms an image by ejecting ink from all the nozzles, whereas the head 90-1 forms an image by ejecting ink from all the nozzles (in FIG. Images are formed by ejecting ink from two nozzles. In this way, when the heads 90-1 and 90-2 have different numbers of nozzles for ejecting ink, a temperature difference is likely to occur between the heads 90-1 and 90-2.

When a temperature difference occurs between the heads 90-1 and 90-2, even if an attempt is made to form an image with the same print density, as in the image Im1 of the images Im shown in FIG. A concentration difference occurs.

For example, when forming the image Im shown in FIG. 13, the temperature of head 90-2 is relatively high and the temperature of head 90-1 is relatively low. Therefore, in the image Im1, as shown in FIG. 13, the print density in the area corresponding to the overlapping part of the heads 90-1 and 90-2 is relatively dark, and the print density in the area corresponding to only the head 90-1 is relatively high. Print density becomes relatively dark.

Therefore, in this modification, the operation display section 112 (receiving section in the present invention) is configured to be able to accept correction points and correction amounts that require correction of print density, and the received correction points and correction amounts are , are input to the head drive section 51, and correction of complementary heat generation amount, which will be described later, is performed.

As an example, referring to the example shown in FIG. 13, the correction location where the print density needs to be corrected is No. 1 of the head 90-1. 2~no. No. 7 of head 90-1, and the user selects nozzle no. 2~no. Nozzle number 7 is input from the operation display unit 112 as the correction location.

Such correction points can be found, for example, by printing a test pattern, reading the printed test pattern with an image reading device, and analyzing the print density. You can enter it from Furthermore, if the correction location determined by the image reading device and the analyzed print density are automatically input to the head driving unit 51, the user does not need to input the correction location and the amount of correction.

Then, the head driving unit 51 corrects the uncorrected complementary heat generation amount to the corrected complementary heat generation amount (see the dotted line), as shown in FIG. 13, based on the input correction location and correction amount. Specifically, the second generation unit B2 corrects the complementary heat generation amount of the nozzle corresponding to the correction location using the correction amount.

As an example, to explain the example shown in FIG. 13, the head 90-1 no. 2~no. Complementary heat generation amount corresponding to nozzle no. 4 and head no. 90-1. 5~no. In the complementary heat generation amount corresponding to the nozzle No. 7, the complementary heat generation amount at the boundary between them is increased from before the correction. Then, the amount of complementary heat generated is gradually decreased in the direction away from the boundary.

For example, head 90-1 no. 2~no. The complementary heat generation amount corresponding to nozzle no. From the part (boundary part) corresponding to nozzle no. It gradually becomes smaller toward the part corresponding to nozzle no. The part corresponding to Nozzle 2 is the same as before correction.

Also, the head 90-1 no. 5~no. The complementary heat generation amount corresponding to nozzle no. From the part (boundary part) corresponding to nozzle no. It gradually becomes smaller toward the part corresponding to nozzle no. The part corresponding to nozzle 7 is the same as before correction.

Here, the changes in the complementary heat generation amount are shown as curves, but when generating the above-mentioned complementary heat generation distribution pattern, the changes in the complementary heat generation amount are represented by shading, and by applying a halftone to this, the complementary heat generation amount can be expressed as a curve. Generated as a calorific value distribution pattern.

Specifically, the sixth pattern generation unit B222 corrects the complementary heat generation amount of the portion corresponding to the correction location in the complementary heat generation amount distribution pattern before correction using the correction amount, and applies halftone to this corrected portion. , generate a corrected complementary calorific value distribution pattern.

By generating dummy pulse data based on the complementary heat generation distribution pattern generated in this way, the temperature difference between the heads 90-1 and 90-2 can be suppressed, and the density difference in printing can be suppressed. .

As described above, in this modification, the image forming apparatus 1 includes the operation display unit 112 that can receive the correction location and correction amount for correcting the complementary heat generation amount. Then, the second generation unit B2 of the head driving unit 51 corrects the complementary heat generation amount of the nozzle corresponding to the correction location using the correction amount to generate a complementary heat generation amount distribution pattern.

According to this modified example configured in this way, it is possible to suppress the temperature difference between the heads, and therefore it is possible to suppress the difference in print density between the heads.

The above-mentioned embodiments and modifications 1 to 3 are merely examples of implementation of the present invention, and the technical scope of the present invention should not be construed as limited by these. It is something. That is, the present invention can be implemented in various forms without departing from its gist or main features.

1 Image forming device 2 External device 10 Paper feed section 20 Image forming section 30 Paper discharge section 50 Head unit 51 Head drive section 90 Inkjet head 91 Substrate 92 Pressure chamber 93 Partition wall 93a First partition wall 93b Second partition wall 93c Joint part 94 Nozzle 95 Nozzle plate 96 Cover plate 97 Common ink chamber 100 Control section 112 Operation display section B1 First generation section B2 Second generation section B211 First pattern generation section B212 Second pattern generation section B213 Third pattern generation section B214 Fourth pattern generation section B22 Sub-pattern generation section B221 Fifth pattern generation section B222 Sixth pattern generation section B223 Seventh pattern generation section B224 Synthesis section B3 Third generation section PE Piezoelectric element

Claims (18)

An inkjet head drive that forms an image by ejecting ink from the plurality of nozzles by driving the piezoelectric elements of each of the plurality of nozzles arranged along the width direction in the inkjet head by applying a drive pulse based on image data. A device,
a first generation unit that generates ejection pulse data having an ejection pulse waveform for driving the piezoelectric element to eject the ink from the image data;
With reference to the correspondence between the pixel value of the pixel of the image data or the ejection pulse waveform of the ejection pulse data and the temperature of the nozzle, find the temperature distribution of the plurality of nozzles in the width direction, and calculate the temperature. a second generation unit that calculates a complementary temperature distribution that complements the distribution of the temperature distribution, and generates dummy pulse data having a dummy pulse waveform for driving the piezoelectric element so as not to eject the ink from the complementary temperature distribution;
a third generation unit that generates the drive pulse based on composite pulse data obtained by combining the ejection pulse data and the dummy pulse data;
An inkjet head drive device comprising: The second generation unit is
a first pattern generation unit that generates an ejection pulse distribution pattern indicating a distribution of the ejection pulse waveform based on the ejection pulse data;
a second pattern generation unit that generates a temperature distribution pattern representing the temperature distribution based on the temperature distribution;
a third pattern generation unit that generates a complementary temperature distribution pattern indicating the complementary temperature distribution based on the temperature distribution of the temperature distribution pattern;
a fourth pattern generation unit that generates a first dummy pulse distribution pattern indicating a distribution of the dummy pulse waveform in which a complementary amount of heat is generated in the piezoelectric element based on the complementary temperature distribution of the complementary temperature distribution pattern;
has
The third generation unit uses the ejection pulse distribution pattern as the ejection pulse data, uses the first dummy pulse distribution pattern as the dummy pulse data, and generates a combination of the ejection pulse distribution pattern and the first dummy pulse distribution pattern. generating the synthesized pulse data based on a pattern synthesized with
The inkjet head driving device according to claim 1. The second generation unit is
a sub-pattern generating unit that obtains a complementary heat generation amount distribution that complements a distribution of heat generation amounts of the piezoelectric elements corresponding to a distribution of the ejection pulse waveform of the ejection pulse data in the width direction, and generates a second dummy pulse distribution pattern that indicates a distribution of a dummy pulse waveform that drives the piezoelectric elements so as not to eject the ink, from the complementary heat generation amount distribution;
a synthesis unit that synthesizes the first dummy pulse distribution pattern and the second dummy pulse distribution pattern to generate a dummy pulse distribution pattern;
having
the third generation unit uses the dummy pulse distribution pattern as the dummy pulse data;
The inkjet head driving device according to claim 2 . The sub-pattern generation section includes:
a fifth pattern generation unit that generates a calorific value distribution pattern indicating the distribution of the calorific value based on the distribution of the ejection pulse waveform in the ejection pulse distribution pattern;
a sixth pattern generation unit that generates a complementary calorific value distribution pattern indicating the complementary calorific value distribution based on the calorific value distribution of the calorific value distribution pattern;
a seventh pattern generation unit that generates the second dummy pulse distribution pattern indicating a distribution of the dummy pulse waveform in which the piezoelectric element generates a complementary amount of heat based on the complementary heat amount distribution pattern; ,
has,
The inkjet head driving device according to claim 3. The fourth pattern generation unit quantizes the complementary temperature distribution pattern to generate the first dummy pulse distribution pattern.
The inkjet head driving device according to claim 2. The fourth pattern generation unit quantizes the complementary temperature distribution pattern using an error diffusion method to generate the first dummy pulse distribution pattern.
The inkjet head driving device according to claim 5. The fourth pattern generation unit quantizes the complementary temperature distribution pattern using a dithering method to generate the first dummy pulse distribution pattern.
The inkjet head driving device according to claim 5. the fifth pattern generation unit applies a spatial filter or a low-pass filter to the ejection pulse distribution pattern to generate the heat generation amount distribution pattern;
5. The inkjet head driving device according to claim 4. The sixth pattern generation unit generates the complementary calorific value distribution pattern by applying a spatial filter to the calorific value distribution of the calorific value distribution pattern.
The inkjet head driving device according to claim 4. the sixth pattern generating unit has an upper limit value of the amount of heat generated by the piezoelectric element, and generates the complementary heat generation amount distribution pattern so as not to exceed the upper limit value.
5. The inkjet head driving device according to claim 4. The seventh pattern generation unit quantizes the complementary heat generation distribution pattern to generate the dummy pulse distribution pattern.
The inkjet head driving device according to claim 4. The seventh pattern generation unit quantizes the complementary heat generation distribution pattern using an error diffusion method to generate the dummy pulse distribution pattern.
The inkjet head driving device according to claim 11. The seventh pattern generation unit quantizes the complementary heat generation distribution pattern using a dithering method to generate the dummy pulse distribution pattern.
The inkjet head driving device according to claim 11. At least two of the inkjet heads are arranged in a staggered pattern along the width direction, and some of the nozzles of the inkjet heads overlap each other in the width direction;
A reception unit capable of receiving a correction portion and a correction amount,
the sub-pattern generation unit corrects the complementary heat generation amount of the nozzle corresponding to the correction portion with the correction amount to generate the complementary heat generation amount distribution.
The inkjet head driving device according to claim 3 . At least two of the inkjet heads are arranged in a staggered pattern along the width direction, and some of the nozzles of the inkjet heads overlap each other in the width direction;
A reception unit capable of receiving a correction portion and a correction amount,
the seventh pattern generating unit corrects the complementary heat generation amount of a portion of the complementary heat generation amount distribution pattern corresponding to the correction portion by the correction amount, to generate the complementary heat generation amount distribution pattern.
5. The inkjet head driving device according to claim 4. An inkjet head that has a plurality of nozzles arranged along the width direction, and forms an image by ejecting ink from the plurality of nozzles by driving each piezoelectric element by applying a drive pulse based on image data. and,
The inkjet head driving device according to claim 1;
Equipped with
Inkjet image forming device. A method for driving an inkjet head, comprising applying a driving pulse based on image data to each piezoelectric element of a plurality of nozzles arranged in a width direction of the inkjet head to eject ink from the plurality of nozzles to form an image, the method comprising the steps of:
generating, from the image data, ejection pulse data having an ejection pulse waveform for driving the piezoelectric element to eject the ink;
determining a temperature distribution in the width direction of the plurality of nozzles by referring to a correspondence relationship between a pixel value of a pixel of the image data or the ejection pulse waveform of the ejection pulse data, and a temperature of the nozzle, determining a complementary temperature distribution that complements the temperature distribution, and generating dummy pulse data having a dummy pulse waveform that drives the piezoelectric element so as not to eject the ink, from the complementary temperature distribution;
generating the driving pulse based on composite pulse data obtained by combining the ejection pulse data and the dummy pulse data;
A method for driving an inkjet head. An inkjet head that forms an image by ejecting ink from the plurality of nozzles by driving the piezoelectric elements of each of the plurality of nozzles arranged along the width direction of the inkjet head by applying a drive pulse based on image data. A driving program,
to the computer,
a process of generating ejection pulse data having an ejection pulse waveform for driving the piezoelectric element to eject the ink from the image data;
With reference to the correspondence between the pixel value of the pixel of the image data or the ejection pulse waveform of the ejection pulse data and the temperature of the nozzle, find the temperature distribution of the plurality of nozzles in the width direction, and calculate the temperature. determining a complementary temperature distribution that complements the distribution of the ink, and generating from the complementary temperature distribution dummy pulse data having a dummy pulse waveform for driving the piezoelectric element so as not to eject the ink;
a process of generating the drive pulse based on composite pulse data obtained by combining the ejection pulse data and the dummy pulse data;
An inkjet head drive program that runs the inkjet head.

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