JP2008265057A - Image forming apparatus and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress viscosity increase of an ink liquid caused at the time of ejection suspension of each nozzle in a spare ejection region where spare ejection to prevent clogging of the nozzle is carried out. <P>SOLUTION: An interval to a front end of the spare ejection region from a timing after ejection in a recording region is determined as a suspension time. Spare ejection is controlled on the basis of conditions for performing the spare ejection setting a timing of performing the spare ejection (or an ejection amount per unit number of times of the spare ejection) to a minimum spare ejection amount necessary for suppressing the viscosity increase of the ink liquid caused at the time of the spare ejection correspondingly to an ejection amount in the recording region and the suspension time for each nozzle. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and a program, and more particularly to an image forming apparatus that suppresses thickening of ink liquid that occurs during preliminary ejection for preventing clogging of a nozzle portion of the image forming apparatus.

  Inkjet recording devices are moving in the direction of increasing the use of water-based pigment inks in order to improve image quality. However, high-viscosity water-based pigment inks use ink at the nozzles of ink-jet recording devices due to evaporation of the solvent. Since it tends to thicken, preliminary discharge must be performed periodically to prevent clogging. However, since the frequency of use and the pause time during which printing is not performed differ for each nozzle, if preliminary ejection is performed based on the same number of ejections for all nozzles, there is a possibility that wasteful ink may be ejected.

  In order to solve these problems, for each of a plurality of nozzles, the preliminary ejection control is performed using the difference between the maximum number of ejections and the number of ejections during image formation of each nozzle as the number of ink ejections of the nozzles during preliminary ejection. Since the number of discharges in the preliminary discharge is set to be equal for each nozzle, wasteful consumption of ink that occurs due to the preliminary discharge exceeding the number of discharges required for the preliminary discharge, and the frequency used during image formation A technique for preventing thickening due to ink evaporation in a nozzle and other nozzles is disclosed (for example, see Patent Document 1).

  In addition, by controlling the ejection amount when ink is ejected in accordance with the recorded image data for each nozzle of the recording head, the difference in wettability inside the nozzle between the used part and the unused part of the nozzle And a technique for eliminating the difference in the amount of oxide film deposited on the surface of the heating resistor element for generating thermal energy for ink ejection inside each nozzle (see, for example, Patent Document 2).

  In addition, when the non-printing time is relatively short, or when there are almost no nozzles with a small number of ejections during printing, depending on the use state of the printing apparatus, preliminary ejection more than the required number may be performed. As the amount of ink used for the ink jet is increased, the running cost increases, and in the case of a cartridge-type ink jet recording apparatus in which the recording head and the ink tank are integrated, the ink tank and the recording head are returned when the ink runs out. The cartridge must be replaced with a new one, and the replacement of the cartridge affects the running cost.

  Therefore, by setting the minimum required number of preliminary discharges based on the number of color or black recording dots, the recording standby time, or the temperature and humidity around the recording head, and using these preliminary discharge numbers, unnecessary ink is used. A technique for reducing the consumption and using the ink efficiently is disclosed (for example, see Patent Document 3).

  Conventionally, when the flushing operation is turned on / off for the nozzle opening in accordance with the ejection or non-ejection of the ink droplet, no consideration is given to the amount of ejected ink, and the nozzle opening is not ejected at all. Since only the flushing operation is performed, if the ejection amount is extremely small even if it is ejected, there is a risk that the ink viscosity will increase at the nozzle opening, depending on whether ejection is performed or not ejected from the nozzle for each scanning unit. A technique for setting the flushing amount of the nozzle and performing flushing based on the set value is disclosed (for example, see Patent Document 4).

  Further, since the discharge heater, which is a source of discharge energy, is exposed to ink, when ink or dirt entering from the outside adheres to the discharge heater, each thermal energy generated in each discharge heater in each nozzle Since each nozzle is different and the droplet diameter generated at each nozzle is also different, discharge is performed by applying a predetermined head drive voltage higher than the head drive voltage during printing to the discharge heater exposed to the ink. There has been disclosed a technique for removing filth from a heater for preventing unevenness in head density during printing (see, for example, Patent Document 5).

Furthermore, in order to prevent unevenness that occurs during printing due to changes in the ink ejection efficiency due to deposits etc. on the surface of the recording head ejection heater, pre-pulse and ink for giving thermal energy that does not shoot into the ink Even if the energy input to the discharge heater of the recording head is the same by controlling the interval time with the main pulse for causing ink to be ejected and ejecting ink from the nozzle in a predetermined condition such as environmental temperature, A technique for preventing unevenness during printing by increasing the discharge amount is disclosed (for example, see Patent Document 6).
JP 05-338134 A Japanese Patent Laid-Open No. 06-305159 Japanese Patent No. 3133869 JP 2005-096281 A Japanese Patent Laid-Open No. 03-256749 Japanese Patent No. 3165552

  However, in order to improve image quality, we are moving toward the use of water pigment inks with higher viscosity. High viscosity water pigment inks tend to thicken at the nozzles due to evaporation of the solvent and prevent clogging. During the preliminary ejection, there is a possibility that the thickening of the ink proceeds due to the ejection or non-ejection of preliminary ejection or the number of ejections in each nozzle portion.

  The techniques disclosed in Patent Documents 1 to 4 are techniques for controlling the number of preliminary ejections for each nozzle according to the frequency of use in order to reduce wasted ink due to preliminary ejection, but the number of preliminary ejections is small. The set nozzles are stopped when other nozzles are performing preliminary ejection, and there is a possibility that the thickening of ink proceeds during the paused time.

  In addition, the techniques disclosed in Patent Documents 5 and 6 are techniques for removing deposits adhering to the discharge heater, but as described above, description of the ink thickening of the nozzle portion that occurs during preliminary discharge. However, there is a possibility that the thickening of the ink progresses during non-ejection.

  The present invention has been made to solve the above-described problem, and an object of the present invention is to suppress the increase in the viscosity of the ink liquid generated in the nozzle portion at the time of preliminary ejection for preventing nozzle clogging.

  In order to achieve the above object, the invention of claim 1 is set by interposing an ejection unit having a plurality of nozzles for ejecting liquid droplets and a pause period in which liquid droplet ejection is suspended after the image forming region. The interval between the last droplet ejection timing in the preliminary ejection region and the start position of the image formation region set after the preliminary ejection region is a cause of droplet thickening in the image formation region. As a result, the number of droplets ejected from each nozzle in the preliminary ejection region is less than the maximum value of the droplet ejection interval that can prevent the landing position deviation of the droplets occurring as follows. Timing determining means for determining a start timing of preliminary ejection; and droplets based on image data are ejected from each nozzle in the image forming area, and the timing is determined in the preliminary ejection area. Is configured to include a control means for controlling said discharging means such ejection of droplets in accordance with the number of times of ejection at the start timing of preliminary ejection is determined by the constant unit begins for each nozzle, the.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the number of droplets ejected from each nozzle in the preliminary ejection region is determined by the total ejection amount of the image forming region and the length of the pause period. It is characterized by that.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the preliminary ejection region and an image forming region after the preliminary ejection region are provided adjacent to each other, and the liquid droplets are finally added. The timing at which the droplets are ejected is the timing at which the last ejected droplet in the preliminary ejection region lands at a position closest to the start position of the image forming region adjacent to the preliminary ejection region.

  A fourth aspect of the present invention is the image forming apparatus according to any one of the first to third aspects, wherein the physical quantity of at least one of temperature and humidity of an environment in which the ejection unit is provided is detected. It further comprises a detecting means, wherein the timing determining means determines the start timing of the preliminary discharge for each nozzle based on the physical quantity and the number of droplets discharged from each nozzle in the preliminary discharge area. .

  A fifth aspect of the present invention is the image forming apparatus according to any one of the first to fourth aspects, wherein the control means is a unit number of droplets ejected from each nozzle in the preliminary ejection region. The ejection unit is controlled so that the per unit ejection amount or the number of ejections per unit time is equal to or greater than the ejection amount per unit number of droplets ejected from each nozzle or the number of ejections per unit time in the image forming region. It is characterized by that.

  According to a sixth aspect of the present invention, there is provided an image forming area in which a discharge means having a plurality of nozzles for discharging droplets and a total discharge amount discharged from the discharge means in the preliminary discharge area are set after the preliminary discharge area In each of the nozzles, the preliminary discharge amount is set to be equal to or larger than a minimum discharge amount that can prevent the landing position deviation of the droplets caused by the thickening of the droplets and less than a predetermined amount larger than the minimum discharge amount. A discharge amount determining unit that determines a discharge amount per unit number of times in the discharge region; and a droplet based on image data is discharged from each nozzle in the image forming region and the discharge amount determining unit in the preliminary discharge region. And control means for controlling the discharge means so that the determined discharge amount of droplets is discharged from each nozzle.

  According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, the discharge amount determining means determines a discharge amount per unit number for each nozzle based on a predetermined number of discharges. And

  According to an eighth aspect of the present invention, in the image forming apparatus according to the sixth aspect, the preliminary ejection region is set by interposing a pause period in which the ejection of liquid droplets is suspended after the image forming region. The discharge amount per unit number of droplets discharged from each nozzle is determined in accordance with the total discharge amount of the image forming region and the length of the pause period.

  A ninth aspect of the present invention is the image forming apparatus according to any one of the sixth to eighth aspects, wherein the physical quantity of at least one of temperature and humidity of an environment in which the ejection unit is provided is detected. The apparatus further includes a detecting unit, wherein the discharge amount determining unit determines a discharge amount per unit number of droplets discharged from each nozzle in the preliminary discharge region based on the physical amount.

  A tenth aspect of the present invention is the image forming apparatus according to any one of the sixth to ninth aspects, wherein the discharge amount determining means is configured to supply droplets discharged from each nozzle in the preliminary discharge area. The ejection amount per unit number is determined so as to be equal to or greater than the ejection amount per unit number of droplets ejected from each nozzle in the image forming region.

  The invention according to an eleventh aspect is the image forming apparatus according to any one of the sixth to tenth aspects, wherein the control means is a unit time of droplets ejected from each nozzle in the preliminary ejection region. The ejection unit is controlled such that the number of times of per unit ejection is equal to or greater than the number of ejections per unit time of droplets ejected from each nozzle in the image forming region.

  According to a twelfth aspect of the present invention, there is provided a program for causing a computer to discharge a droplet last in a preliminary discharge region set through a pause period in which the discharge of the droplet is suspended after the image forming region; Liquid droplets that can prevent the landing position deviation of the liquid droplets caused by the thickening of the liquid droplets in the image forming region from the interval between the preliminary ejection region and the start position of the image forming region. Timing determining means for determining the start timing of preliminary discharge for each nozzle based on the number of droplets discharged from each nozzle that discharges droplets in the preliminary discharge region so as to be equal to or less than the maximum value of the discharge interval; Droplets based on image data are ejected from the nozzles in the image forming area, and the preliminary ejection determined by the timing determining means in the preliminary ejection area. And a control means for discharge of droplets in accordance with the number of times of ejection at the start timing of control to be started for each nozzle is a program for causing to function.

  According to a thirteenth aspect of the invention, there is provided a program for causing a computer to increase the number of droplets in an image forming area in which the total discharge amount discharged from each nozzle for discharging droplets in the preliminary discharge area is set after the preliminary discharge area. The number of unit times in the preliminary discharge region for each nozzle so that the amount of the landing position of the droplet caused by the viscosity is not less than a minimum discharge amount that can be prevented and less than a predetermined amount larger than the minimum discharge amount. A discharge amount determining unit that determines a per unit discharge amount, and droplets based on image data in the image forming region are discharged from each nozzle, and the discharge amount determined by the discharge amount determining unit in the preliminary discharge region Is a program for functioning as control means for controlling the liquid droplets to be discharged from each nozzle.

  As described above, according to the first aspect of the invention, by controlling the start timing for performing the preliminary discharge for each nozzle, it is possible to suppress the increase in the viscosity of the droplets generated in the nozzle portion during the preliminary discharge. There is an effect that it is possible.

  According to the invention concerning Claim 2, there exists an effect that the frequency | count of discharge more than necessary at the time of preliminary discharge can be reduced.

  According to the third aspect of the invention, it is possible to further reduce the time during which the nozzle portion is in contact with the outside air, and it is possible to more reliably suppress the thickening of the droplet caused by the evaporation of the droplet. Play.

  According to the fourth aspect of the present invention, it is possible to more accurately suppress the thickening of the droplet that occurs during the preliminary discharge by considering the temperature and the humidity that affect the speed of the thickening of the droplet. It has the effect of becoming.

  According to the fifth aspect of the invention, there is an effect that the printing cycle in the image forming apparatus can be shortened, that is, the printing speed can be improved.

  According to the sixth aspect of the invention, by controlling the discharge amount per unit number of times in the preliminary discharge region for each nozzle, it is possible to suppress the progress of the thickening of the droplets that occurs during the preliminary discharge. , Has the effect.

  According to the seventh aspect of the invention, it is possible to reduce the processing load of the image forming apparatus during preliminary ejection and to improve the processing speed.

  According to the eighth aspect of the invention, it is possible to reduce the amount of liquid droplets that are more than necessary during preliminary discharge.

  According to the ninth aspect of the present invention, it is possible to more accurately suppress the thickening of the liquid droplet that occurs during the preliminary discharge by considering the temperature and humidity that affect the speed of the thickening of the liquid droplet. It has the effect of becoming.

  According to the invention which concerns on Claim 10, there exists an effect that the printing cycle can be shortened, ie, the printing speed can be improved.

  According to the eleventh aspect of the invention, there is an effect that the printing speed in the image forming apparatus can be improved.

  According to the twelfth aspect of the present invention, it is possible to provide a program that suppresses the thickening of droplets generated in the nozzle portion during preliminary discharge by controlling the start timing for performing preliminary discharge for each nozzle. The effect of becoming.

  According to the thirteenth aspect of the present invention, there is provided a program for controlling the progress of the thickening of droplets that occurs during preliminary discharge by controlling the discharge amount per unit number in the preliminary discharge region for each nozzle. There is an effect that becomes possible.

[First embodiment]
Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. In the first embodiment, the present invention is applied to an ink jet printer as an image forming apparatus.

  FIG. 1 is a diagram showing a schematic configuration diagram of an ink jet printer according to the first embodiment.

  As shown in FIG. 1, the inkjet printer 10 forms an image on the recording paper P by ejecting ink droplets, a paper supply unit 12 that feeds the recording paper P, a registration adjusting unit 14 that controls the posture of the recording paper P, and the like. The recording head unit 16 and the recording unit 20 provided with the maintenance unit 18 that performs maintenance of the recording head unit 16 and a discharge unit 22 that discharges the recording paper P on which an image is formed by the recording unit 20 are basically configured. .

  The paper supply unit 12 includes a paper supply unit 24 that stores the recording paper P and a conveyance device 26 that takes out the paper from the paper supply unit 24 one by one and conveys it to the registration adjustment unit 14. The registration adjusting unit 14 includes a loop forming unit 28 and a guide member 30 that controls the posture of the recording paper P. The recording paper P passes through this portion and is skewed using its elasticity. Is corrected, and the conveyance timing is controlled and supplied to the recording unit 20. The discharge unit 22 discharges the recording paper P on which the image is formed by the recording unit 20 to the paper discharge unit 34 via the paper discharge belt 32.

  Between the recording head unit 16 and the maintenance unit 18, a paper transport path 36 through which the recording paper P is transported is provided (the paper transport direction is indicated by an arrow PF). The paper conveyance path 36 has a star wheel 38 and a conveyance roll 40, and conveys the recording paper P between the star wheel 38 and the conveyance roll 40 continuously (without stopping). Then, ink droplets are ejected from the recording head unit 16 to the recording paper P, and an image is formed on the recording paper P. The maintenance unit 18 includes a maintenance device 44 disposed to face the ink jet recording unit 42, and performs capping and wiping on the recording head 46 having a plurality of nozzles for ejecting ink liquid, as well as preliminary ejection and vacuum. And so on.

  Each inkjet recording unit 42 records an image on the recording paper P by ejecting ink droplets from the recording heads 46 to the recording paper P that is continuously transported through the paper transport path 36. In order to record a full-color image, the inkjet recording unit 42 is arranged at least one unit for each color of yellow (Y), magenta (M), cyan (C), and black (K).

  Each ink jet recording unit 42 is provided with a temperature sensor 48 that detects its own environmental temperature, and the ink jet printer 10 is further provided with a humidity sensor 50 that detects the environmental humidity in the vicinity of the ink jet recording unit 42.

  Next, the configuration of the control system of the inkjet printer 10 according to the first embodiment configured as described above will be described. FIG. 2 is a block diagram showing the configuration of the control system of the inkjet printer 10 according to the first embodiment.

  In the ink jet printer 10 according to the first embodiment, a control controller 100 configured by a computer including a RAM as a primary storage medium, a ROM (for example, an EEPROM) as a writable storage medium, and a CPU includes a drive IC 102. By controlling, the driver 104 that drives the ejection of ink from each recording head 46 is driven to eject ink droplets from each recording head 46.

  The drive IC 102 includes a shift register 106, a latch circuit 108, shift registers 110 </ b> A to 110 </ b> P, a selector 112, and a level shifter 114, and a clock signal and a drive waveform selection signal output from the control controller 100 are shifted. The signal is input to the register 106 and the latch signal is input to the latch circuit 108.

  The drive waveforms generated by the waveform generation circuit 116 are input to the shift registers 110A to 110P. The waveform generation circuit 116 generates, for example, 16 types of drive waveforms, and stores the generated drive waveforms in the shift registers 110A to 110P. In the first embodiment, the 16 types of drive waveforms are assigned the first to fourth large droplet waveforms predetermined as the first to fourth drive waveforms, and the first to first predetermined as the fifth to eighth drive waveforms. The fourth medium droplet waveform is assigned, and the first to fourth droplet waveforms predetermined as the ninth to twelfth drive waveforms are assigned.

  Then, according to the ejection amount at the time of image formation for each nozzle and the pause time from the end of image formation to the start of preliminary ejection, etc., each of the four types of large droplet waveform, medium droplet waveform, and small droplet waveform The driving waveform is selected from the above, and used for preliminary ejection for suppressing the increase in the viscosity of the ink liquid for each nozzle, and the remaining waveform is used as a spare.

  The selector 112 and the level shifter 114 are provided for each driver 104 that drives each piezoelectric element 120. The selector 112 receives 4-bit data for selecting 16 types of drive waveforms for each ejection cycle. ˜110P, the drive waveform selected by the selector 112 is raised to a predetermined voltage by the level shifter 114 and output to the driver 104. The driver 114 is connected to the ground, the voltage HV1, and the voltage HV2 through three switching elements 118A, 118B, and 118C (118), respectively, and the drive waveform is turned on and off by the switching elements 118A, 118B, and 118C. Applied to the piezoelectric element 120.

  The controller 100 is connected to a temperature sensor 48 that detects the environmental temperature of each recording head 46 and a humidity sensor 50 that detects the environmental humidity in the vicinity of each recording head 46. The control controller 100 includes the temperature sensor 48. And the detection result of the humidity sensor 50 is acquired, and waveform selection, ink supply, etc. are controlled.

  In the first embodiment, a digital drive waveform is generated using three types of 0 (GND), voltage HV2, and voltage HV1 (HV2> HV1). In the first embodiment, ink droplets of three types of droplet amounts are ejected using the ternary digital drive waveform. Hereinafter, the three types of ink droplets are referred to as large droplets, medium droplets, and small droplets in descending order of droplet amount.

  FIG. 3 shows an example of a driving waveform applied to the piezoelectric element 120 applied in the first embodiment, and FIG. 3A shows an example showing a driving waveform of a large droplet, and FIG. Fig. 3C shows an example showing the drive waveform of a medium droplet, Fig. 3C shows an example of the drive waveform of a small droplet, and Fig. 3D shows a slight vibration applied to a nozzle that does not discharge. The preliminary waveform which is a drive waveform for suppressing the viscosity increase of an ink is shown.

  Table 1 below shows examples of the droplet volume and the droplet velocity of the ink droplets ejected by the drive waveform. The drop speed, which is the drop speed of ink drops, is, for example, 10 m / sec for all drop types in order to align the landing positions between the drop types such as large drops, medium drops, and small drops that indicate the type of ink drop size. It is set to become. The drop volume varies depending on the type of drop used depending on the gradation of the recording data. For example, the large drop is set to 10 pl, the medium drop is set to 6 pl, and the small drop is set to 2.5 pl, for example.

  These drive waveforms are based on a predetermined potential. When the voltage decreases, the pressure chamber (not shown) in which the ink liquid is stored expands. When the voltage increases, the pressure chamber contracts, and the pressure chamber expands and contracts. As a result, the volume of the pressure chamber is increased or decreased to eject ink droplets from the recording head 46.

  FIG. 4A shows a pause time (details will be described later) during which ink droplet ejection is paused after image formation and a drop velocity of the first ink droplet ejected after the pause time when an aqueous pigment ink is used. It shows the relationship. In the rest period, a preliminary waveform is given by applying a predetermined voltage to the piezoelectric element 120. When the pause time is lengthened, the ink droplets at the nozzle portion increase in the viscosity of the ink liquid due to the evaporation of the solvent, and the droplet speed becomes slow. In FIG. 4A, the drop speed (reference speed) at the time of continuous printing is, for example, 10 m / sec. As the drop volume becomes smaller, the drop speed is more easily affected by the increase in the viscosity of the ink liquid. growing.

  4B, as shown, the ejection frequency is 18 kHz, the printing direction resolution is 1200 dpi, the scanning speed is 381 mm / sec, the distance between papers is 1.0 mm, and the reference speed is 10.0 m / second, for example. This shows the relationship between the droplet speed and the amount of ink droplet landing position deviation from the ideal landing position on the recording paper P when printing under the sec condition, and the ink droplet droplet speed is slow. As a result, the amount of landing position deviation increases.

  FIG. 5 shows the relationship between the rest time and the landing position deviation amount of the ink droplets ejected first after the rest time from the relationship between FIG. 4 (A) and FIG. 4 (B). As the pause time increases, the droplet speed decreases and the landing position deviation increases. For example, when the droplet type is a small droplet, the landing position deviation amount is, for example, 10 μm if the pause time is, for example, 0.6 sec. If the printing direction resolution is, for example, 1200 dpi, the dot pitch in the printing direction is, for example, 21 μm. If the positional deviation amount is, for example, 10 μm, the half-pitch deviation occurs. The smaller the droplet volume, the larger the landing positional deviation amount.

  FIG. 6 shows the relationship between parameters when the recording head 46 and the recording paper P are relatively scanned and printed.

  In the first embodiment, for each parameter, the droplet velocity is Vd (m / sec), the distance between the recording paper P and the recording head 46 is d (m), the printing direction resolution is n (dpi), The ejection frequency is defined as f (kHz), the ejection cycle is defined as T0 (μsec) = 1000 / f, and the scanning speed is defined as Vs (m / sec) = 25.4 × f ÷ n.

  In the first embodiment, as the values of the above parameters, for example, the distance between sheets is d (m) = 0.001, the resolution in the scanning direction is n (dpi) = 1200, and the ejection frequency is f (kHz) = 18. 0.0, discharge period T0 (μsec) = 1000 / f = 55.6, and scan speed Vs = (m / sec) = 25.4 × f ÷ n = 0.382.

  Furthermore, if the drop speed difference due to the thickening of the ink liquid is ΔVd (m / sec) with respect to the drop speed (reference speed) Vd during continuous printing, the ink is ejected from the recording head 46 and landed on the recording paper P. The landing time difference is ΔT (sec) = {d / (Vd ± ΔVd)} − {d / Vd}, and the landing position deviation amount from the ideal landing position on the recording paper P is ΔL = Vs × ΔT. It is defined as

  In FIG. 7, recording heads 46 (for example, A4 longitudinal width) are provided for four colors (YMCK), and the recording paper P is placed on a recording paper transport belt (not shown) facing the recording heads 46. There is no existing recording area and recording paper P, and there is a preliminary ejection area for performing preliminary ejection to prevent clogging of the nozzle portion, and there is a margin area between the areas.

  In the preliminary ejection region, ink droplets are ejected directly onto the paper transport belt. After preliminary ejection, the ink droplets ejected onto the paper transport belt are cleaned with a cleaner (not shown). The discharge interval of the preliminary discharge in the preliminary discharge region is the same as the discharge interval in the recording region, for example, 21 μm (1200 dpi). In the preliminary discharge region, the four colors of YMCK ink are at the same position on the paper transport belt. Be landed.

  Table 2 below illustrates the conventional recording area, preliminary ejection area, and margin area. In this example, the aqueous pigment ink is large in order to refresh nozzles that were not ejected at all in the recording area after the preliminary ejection. A pre-discharge of 500 pulses is required with a drop of 10 pl. In this example, the A4 printing cycle is 0.604 sec, and the printing speed is 99.3 ppm.

  FIG. 8A shows an example of a method for classifying the ejection amount required for preliminary ejection in the preliminary ejection region. The required preliminary discharge amount is W (pl), the discharge amount of the recording area is V (pl), and the pause time is t (sec), and is classified as a dotted line area shown in FIG. The worst condition in the dotted line area is indicated by a black circle. The worst condition is a condition in which V is the smallest and t is the largest in each dotted line region.

  For example, when the ejection amount V of the recording area indicates a value between 1000 and 3000 (pl) and the pause time t indicates a value between 0.2 and 0.4, the worst condition is that of the recording area. The discharge amount V is 1000 (pl), and the rest time t is 0.4 (sec).

  FIG. 8B shows an experiment (details will be described later) for obtaining the required preliminary discharge amount W under the worst conditions in each dotted line region shown in FIG. 8A described above. The required preliminary discharge amount W is shown. For example, when the ejection amount V of the recording area shows a value between 1000 and 3000 (pl) and the pause time t shows a value between 0.2 and 0.4, the necessary preliminary ejection amount W is 2500. (Pl).

  FIG. 9 shows an experimental sequence for obtaining the necessary preliminary discharge amount W. First, a standard printing cycle is executed several times with a discharge amount in the reference recording area and a discharge amount in the preliminary discharge area to create a steady state, and then a parameter experiment is performed.

  This parameter experiment is performed in the parameter experiment area in FIG. 9, and the parameters to be used are the necessary preliminary ejection amount W (pl), the ejection amount V (pl) of the recording area, and the pause time t (sec). The characteristic value for determining the preliminary discharge amount W (pl) is the landing position deviation amount from the ideal landing position when the droplet type is a small droplet. As described above, the experiment is performed by setting V and t as the worst condition and changing W.

  After the preliminary discharge in the parameter experiment area is completed, a small droplet that is easily affected by the pause time is discharged, and if the landing position deviation amount is within a predetermined specified range, the minimum preliminary discharge amount is determined under the worst condition. The required preliminary discharge amount W is obtained. The landing position deviation amount is set based on the target image quality and can be half of the image pitch in the printing direction. For example, when the image pitch in the printing direction (scanning direction) is 21 μm, it is 10.5 μm, which is half of the image pitch. To do.

  10 to 12 show a setting method of the preliminary ejection pulse at the time of preliminary ejection according to the ejection amount and the rest time in the recording area.

  In FIG. 10, the preliminary discharge amount W obtained in accordance with the discharge amount V and the pause time t of the recording area is set. The discharge amount V, the pause time t and the discharge time V of the print area shown in FIG. This corresponds to the necessary preliminary discharge amount W. In the first embodiment, the droplet type for each nozzle is unified as a large droplet.

  As shown in FIG. 11, the pause time indicates an interval between the timing at which ink droplets are finally ejected in a recording area where an image is formed and the timing at which preliminary ejection is started in the preliminary ejection area.

  FIG. 12 shows an example relating to the arrangement of the preliminary ejection pulses. FIG. 12A conventionally illustrates that the preliminary ejection pulses that differ for each nozzle are ejected with reference to the front end of the preliminary ejection area, and the number of ejections. In the case of a high viscosity pigment ink in recent years, the increase in the viscosity of the ink liquid has progressed with a nozzle having a small number of inks. The impact is growing.

  For this reason, as shown in FIG. 12B, in the first embodiment, a slight timing difference between the timing of the last ink droplet ejection in the preliminary ejection area and the start position of the recording area after the preliminary ejection area. In order to prevent thickening of the ink liquid due to, by setting the preliminary ejection pulse of each nozzle based on the position closest to the start position of the recording area adjacent to the preliminary ejection area, that is, the rear end of the preliminary ejection area, The time during which the nozzle portion is in contact with the outside air is further shortened, and the thickening of the ink due to the evaporation of the ink liquid is more reliably suppressed.

  Therefore, with respect to the preliminary ejection amount corresponding to the total ejection amount and the rest time of the recording area shown in FIG. 10, the rear end of the preliminary ejection area, that is, the timing at which ink droplets are finally ejected in the preliminary ejection area is used as a reference. The number of preliminary discharges is determined, and the preliminary discharge conditions, which are the conditions for performing the preliminary discharge shown in FIG. 10, are stored in the storage medium such as the ROM described above.

  Furthermore, in order to more accurately suppress the thickening of the ink liquid that occurs during the preliminary ejection, the above experiment was performed in consideration of the progress speed of the thickening of the ink liquid that varies depending on the temperature and humidity, and a diagram corresponding to the temperature and humidity. It is also possible to store the preliminary discharge conditions shown in FIG.

  By setting the preliminary ejection pulse as described above, the number of ejections is determined according to the total ejection amount during image formation and the length of the pause time, so the number of ejections more than necessary during preliminary ejection is reduced. it can.

  Next, FIG. 13 is a flowchart showing an example of processing performed by the controller 100 in the inkjet printer 10 according to the first embodiment.

  In step 100, the environmental temperature of each recording head 46 measured by the temperature sensor 48 is stored in the RAM of the controller 100. In the next step 102, the environmental humidity in the vicinity of the recording head 46 measured by the humidity sensor 50 is stored in the RAM. To do.

  In the next step 104, a nozzle to be subjected to preliminary ejection is selected, and in the next step 106, the total ejection amount at the time of image recording in the recording area of the nozzle selected in step 104 is measured based on the image data. In the next step 108, the pause time of the selected nozzle is calculated.

  As a calculation method of the pause time, for example, the timing when the pixel data of the nozzle selected in Step 104 is completely free of “1” (there is print data in the print area, that is, the ink droplet is ejected) is the start timing of the pause time. A time corresponding to the number of remaining pixel data '0' (no recording data in the recording area, that is, no ink droplet ejection) is defined as a pause time in the recording area.

  On the other hand, when a margin is set between the recording area and the preliminary ejection area, the time required for each recording head 46 to pass the margin (for example, a value obtained by dividing the length of the margin by the scanning speed Vs). The time stored in advance in the ROM and the time acquired from the ROM is added to the pause time in the recording area is referred to as pause time.

  In the next step 110, the temperature and humidity of the recording head 46 stored in the RAM in steps 100 and 102 are read out, and the temperature and humidity, and the total ejection amount of the nozzle recording area calculated in steps 106 and 108, and The preliminary ejection droplet type, preliminary ejection number, and preliminary ejection frequency, which are preliminary ejection conditions stored in advance in the ROM corresponding to the pause time calculated in step 108, are acquired.

  In step 112, when the preliminary discharge conditions are acquired for all the nozzles, the process proceeds to step 114. When there are nozzles for which the preliminary discharge conditions are not acquired, the process returns to step 104 again, and the preliminary discharge conditions are set. Steps 104 to 112 are performed on the nozzles that have not been acquired.

  In step 114, preliminary ejection is performed based on the preliminary ejection conditions acquired in step 110. When performing preliminary ejection, as shown in FIG. 12B, the timing of starting preliminary ejection for each nozzle in the preliminary ejection area differs according to temperature, humidity, ejection amount of the recording area, and pause time. As the start timing, for example, the time for the recording head 46 to pass through the preliminary ejection area is stored in advance in the ROM as a design value, and the ink droplets ejected at the time of preliminary ejection are stored from the passage time in advance. By multiplying the discharge interval by the number of preliminary discharges and subtracting a value obtained by multiplying by the scan speed Vs, the timing for starting the preliminary discharge from the front end of the preliminary discharge region is calculated.

  After the timing is calculated, a drive waveform corresponding to the preliminary discharge droplet type of the ink liquid is selected for each nozzle based on the preliminary discharge condition acquired in step 110, and the preliminary discharge is controlled at the calculated timing. To do.

  As a result, the preliminary ejection is performed with a predetermined number of preliminary ejections based on the ink droplet ejected at the end of the preliminary ejection area where the preliminary ejection is performed, so the viscosity of the ink liquid generated in the nozzle portion during the preliminary ejection is increased. Can be suppressed.

  That is, it is the timing when the last ink droplet ejected in the preliminary ejection area lands on the position closest to the start position of the image forming area adjacent to the preliminary ejection area.

  In the above description, regarding the setting of the preliminary discharge pulse, an example is described in which the rear end of the preliminary discharge region is set as the end timing of the preliminary discharge as shown in FIG. However, the timing at which the preliminary discharge is started may be determined based on a position other than the rear end in the preliminary discharge region without using the rear end of the preliminary discharge region as a reference.

  In this case, the interval between the timing at which the last ink droplet is ejected in the preliminary ejection area and the start position of the recording area set after the preliminary ejection area prevents the landing position deviation of the ink droplet in the recording area. The timing at which ink droplets are finally ejected in the preliminary ejection region is determined so that the interval can be less than the maximum value that can be performed, and this timing is used as a reference for each nozzle based on a predetermined number of preliminary ejections. The start timing for performing preliminary discharge is determined.

  In this case, for example, a predetermined time from the front end of the preliminary ejection area to the last ink droplet ejection timing in the preliminary ejection area is stored in advance in the ROM as a design value. By subtracting the quotient obtained by dividing the product of the ejection interval of each ink droplet ejected at the time of ejection by the number of preliminary ejections and dividing by the scan speed Vs, the timing for starting the preliminary ejection with reference to the front end of the preliminary ejection region is calculated. .

  As a result, the thickening of the ink liquid that occurs during the downtime, and the ink liquid that occurs between the timing at which the droplets are finally ejected in the preliminary ejection area and the start position of the image forming area that is set after the preliminary ejection area. It becomes possible to suppress the progress of thickening.

  Further, in the above description, the example in which the timing for starting the preliminary discharge is determined using the temperature and humidity as one of the parameters has been described. However, the timing for starting the preliminary discharge may be determined using either one of the temperature and the humidity. The timing for starting the preliminary discharge may be determined without including the temperature and humidity in the parameters.

[Second Embodiment]
In the first embodiment, when the increase in the viscosity of the ink liquid is suppressed in the preliminary discharge region, the preliminary discharge amount and the preliminary discharge number are set according to the discharge amount and the pause time of the recording region. In the second embodiment, the preliminary ejection is controlled for each nozzle by setting different preliminary ejection droplet types.

  The configuration of the ink jet printer and the control system of the ink jet printer according to the second embodiment is the same as that of the first embodiment shown in FIGS.

  As in the first embodiment, the parameters used in the second embodiment are the necessary preliminary ejection amount W (pl), the ejection amount V (pl) of the recording area, and the pause time t (sec). The characteristic value for determining the discharge amount W (pl) is the landing position deviation amount from the ideal landing position of the droplet. Further, the experiment is performed by setting V and t as the worst condition and changing W.

  After the preliminary discharge in the parameter experiment area is completed, a small droplet that is easily affected by the pause time is discharged, and if the landing position deviation amount is within a predetermined specified range, the minimum preliminary discharge amount is determined under the worst condition. The required preliminary discharge amount W is obtained.

  Hereinafter, a preliminary discharge setting method according to the discharge amount and the pause time in the recording area will be described. In the second embodiment, the preliminary ejection amount is set by setting different preliminary ejection droplet types with the same number of preliminary ejections for each nozzle. Accordingly, the ratio of the preliminary discharge amount of each nozzle is the ratio of the drop volume of the set drop type.

  FIG. 14 shows the setting of the preliminary discharge amount W obtained according to the discharge amount V of the recording area and the pause time t based on the above-described experimental results. The preliminary discharge amount W is the same as that shown in FIG. Is set to be a preliminary discharge amount equal to or larger than the discharge amount V, the pause time t, and the necessary preliminary discharge amount W in the recording area shown in FIG.

  Accordingly, the preliminary discharge droplet type is determined for the preliminary discharge amount corresponding to the discharge amount and the rest time of the recording area shown in FIG. 14, and the preliminary discharge is a condition for performing the preliminary discharge shown in FIG. The discharge conditions are stored in the storage medium such as the ROM as described in the first embodiment.

  Further, as described in the first embodiment, in order to more accurately suppress the thickening of the ink liquid that occurs during the preliminary discharge, the above-mentioned speed is considered in consideration of the progress of the thickening of the ink liquid depending on the temperature and humidity. An experiment is performed, and the preliminary discharge conditions shown in FIG. 14 corresponding to temperature and humidity are stored in the ROM.

  As described above, it is not necessary to set the number of preliminary discharges simply by setting the discharge amount per unit number of times (preliminary discharge droplet type) for each nozzle, thereby reducing the transfer amount of data used for discharge processing. Therefore, it is possible to reduce the processing load of the image forming apparatus during preliminary ejection and improve the processing speed.

  Furthermore, since the discharge amount per unit number of droplets is determined according to the discharge amount during image formation and the length of the pause time for each nozzle, the amount of droplet discharge more than necessary during preliminary discharge is reduced. can do.

  Next, the processing performed by the controller in the inkjet printer according to the second embodiment is the same as Step 100 to Step 112 of the flowchart shown in FIG. In the second embodiment, in step 114, the preliminary discharge start timing is set at the front end of the preliminary discharge area as in the conventional case, and the preliminary discharge droplet types, the number of preliminary discharges, and the preliminary discharge conditions stored in the ROM are stored. Preliminary ejection is controlled based on the preliminary ejection frequency.

  As a result, preliminary ejection is performed by setting the preliminary ejection droplet type of the ink liquid for which preliminary ejection is performed for each nozzle, so that it is possible to suppress the increase in the viscosity of the ink liquid generated in the nozzle portion during preliminary ejection.

  In the above, the number of preliminary discharges for each nozzle is the same, but it is not necessary to be the same for all nozzles, and the total discharge amount discharged from the nozzles in the preliminary discharge area is set after the preliminary discharge area. The minimum discharge amount that can prevent the landing position deviation of the ink droplets caused by the increase in the viscosity of the ink liquid in the formed image forming area and not more than a predetermined amount more than the minimum discharge amount, preferably the minimum discharge amount Thus, by determining the discharge amount (preliminary discharge droplet type) per unit number of times in the preliminary discharge region for each nozzle, control is performed so as to suppress the progress of thickening of the ink liquid that occurs during the preliminary discharge. It is also possible.

  When the total discharge amount in the preliminary discharge region is set to an amount exceeding the above-mentioned minimum discharge amount, it is preferably the minimum for reducing the ink consumption, and more preferably 0.

  Further, in the above description, the example in which the timing for starting the preliminary discharge is set with the temperature and humidity as one of the parameters has been described, but the preliminary discharge is started using either the temperature or the humidity as in the first embodiment. The timing for starting the preliminary ejection may be determined without including the temperature and humidity in the parameters.

[Third embodiment]
In the third embodiment, ink generated during preliminary ejection is set by setting the preliminary ejection droplet type or ejection frequency of the ink liquid in the preliminary ejection area to a droplet amount larger than the droplet type or ejection frequency of the ink liquid in the recording area. In addition to suppressing the increase in the viscosity of the liquid, it is possible to quickly discharge the discharge amount required for the preliminary discharge, thereby shortening the time required for the preliminary discharge.

  Since the ink jet printer according to the third embodiment has the same configuration as that of the first embodiment, description thereof is omitted.

  The configuration of the control system of the ink jet printer according to the third embodiment is the same as that of the control system of the ink jet printer shown in FIG. 2 of the first embodiment and the second embodiment, and the same parts are denoted by the same reference numerals. Description will be omitted with reference to the drawings, and only the differences from the first and second embodiments will be described.

  In the third embodiment, the drive waveforms generated by the waveform generation circuit 116 are input to the shift registers 110A to 110P, and the waveform generation circuit 116 generates a plurality of drive waveforms, for example, 16 types of drive waveforms. The generated drive waveforms are stored in the shift registers 110A to 110P. In the third embodiment, the 16 types of drive waveforms are assigned the first to third large droplet waveforms predetermined as the first to third drive waveforms, and the first to third predetermined drive waveforms are assigned to the fourth to sixth drive waveforms. The third medium droplet waveform is allocated, the first to third droplet waveforms predetermined as the seventh to ninth drive waveforms are allocated, and in the third embodiment, the tenth predetermined waveform is determined as the tenth to twelfth drive waveforms. 1st to 3rd maximum droplet waveform is assigned.

  Then, each of the maximum droplet waveform, the large droplet waveform, the medium droplet waveform, and the small droplet waveform 4 according to the total discharge amount at the time of image formation for each nozzle and the rest time from the end of the image formation to the start of the preliminary discharge. A drive waveform is selected from the types and used for preliminary ejection in order to suppress thickening of the ink liquid for each nozzle, and the remaining waveform is used as a spare.

  Hereinafter, the four types of ink droplets are referred to as a maximal droplet, a large droplet, a medium droplet, and a small droplet in descending order of the droplet amount.

  In addition, the selector 112 and the level shifter 114 are provided for each driver 104 that drives each piezoelectric element 120, and the selector 112 shifts 4-bit data for selecting 16 types of driving waveforms for each ejection cycle. The drive waveform input from the registers 110A to 110P and selected by the selector 112 is raised to a predetermined voltage by the level shifter 114 and output to the driver 104. The driver 114 is connected to the ground (GND), the voltage HV1, and the voltage HV2 through three switching elements 118A, 118B, and 118C (118), respectively, and the switching elements 118A, 118B, and 118C are turned on and off. A drive waveform is applied to the piezoelectric element 120.

  Further, a temperature sensor 48 that detects the environmental temperature of each recording head 46 and a humidity sensor 50 that detects the environmental humidity of the recording head 46 are connected to the controller 100. The controller 100 includes the temperature sensor 48 and humidity. The detection result of the sensor 50 is acquired, and waveform selection, ink supply, and the like are controlled.

  In the third embodiment, a digital drive waveform is generated using three types of 0 (GND), voltage HV2, and voltage HV1 (HV2> HV1). Further, four types of ink droplets are ejected using the ternary digital drive waveform. FIG. 15 shows an example of a drive waveform applied to the piezoelectric element 120 applied in the third embodiment, and FIG. 15A shows an example of a drive waveform of a maximal droplet, and FIG. FIG. 15C shows an example showing the drive waveform of a large droplet, FIG. 15C shows an example of the drive waveform of a medium droplet, and FIG. 15D shows an example of the drive waveform of a small droplet. Further, FIG. 15E shows a preliminary waveform which is a drive waveform for giving a slight vibration to a nozzle which is not ejected to suppress ink thickening.

  In order to shorten the time required for the preliminary ejection, the maximum droplet amount and ejection frequency of the preliminary ejection droplet type of the preliminary ejection ink liquid are increased. As shown in Table 3 below, the droplet type of the ink liquid is larger than that of the large droplet. Also set a maximum drop with a large drop volume. Since the maximum droplet is not used at the time of image formation in the recording area, as shown in Table 3, it is not necessary that the droplet speed of the maximum droplet is the same as other droplet types.

  As shown in FIG. 16, the preliminary discharge amount W obtained in accordance with the discharge amount V and the pause time t of the recording area is set according to the above-described experimental results, and the recording area shown in FIG. The preliminary discharge amount is set to be equal to or greater than the discharge amount V, the pause time t, and the necessary preliminary discharge amount W.

  As shown in Table 3, the maximum droplet volume is set to 16.0 pl, and the droplet type is set as shown in FIG. 16, thereby ensuring the equivalent preliminary discharge volume shown in FIG. 500 pulses can be reduced to 310 pulses, and the preliminary discharge time can be shortened.

  Also, as shown in FIG. 16, the preliminary ejection time can be shortened by setting the preliminary ejection frequency as high as 24.0 Hz.

  Accordingly, the number of preliminary discharges is determined for the preliminary discharge amount and the preliminary discharge droplet type corresponding to the discharge amount and the rest time of the recording area shown in FIG. 16, and the conditions for performing the preliminary discharge shown in FIG. Are stored in the storage medium such as the above-mentioned ROM, and the viscosity of ink changes according to at least one of temperature and humidity. Therefore, considering at least one of temperature and humidity The above experiment may be performed, and the preliminary discharge conditions shown in FIG. 16 corresponding to the temperature and humidity may be stored in the ROM.

  The processing performed by the control controller in the ink jet printer according to the third embodiment is the same as Step 100 to Step 112 of the flowchart shown in FIG. 13 described in Embodiment 1 and Embodiment 2, and therefore description thereof is omitted. In step 114, the timing of starting the preliminary discharge may be the timing described in the first embodiment or the second embodiment, but the droplet amount is reserved in addition to the first embodiment and the second embodiment. The maximum droplet is set in the ROM as the ejection droplet type, and a drive waveform corresponding to the preliminary ejection droplet type of the ink liquid is selected for each nozzle to control the preliminary ejection.

  In summary, as shown in Table 4 below, the printing cycle can be shortened to 0.590 with respect to the printing cycle of 0.604 sec in Table 2. As a result, the printing speed can be increased from 99.3 ppm to 101.8 ppm.

  Such an increase in printing speed is effective, for example, for an image forming apparatus such as a high-speed inkjet using an FWA head in which the time spent for preliminary ejection affects speeding up.

  As described above, the preliminary ejection droplet type that is the ejection amount per unit number of ink droplets ejected from each nozzle in the preliminary ejection region and the ejection frequency that is the preliminary ejection number per unit time are the droplet type of the ink liquid in the recording region and By setting it to be higher than the discharge frequency, while suppressing the increase in the viscosity of the ink liquid generated in the nozzle part during the preliminary discharge, the time required for the preliminary discharge can be reduced by quickly discharging the discharge amount required for the preliminary discharge. This makes it possible to shorten the printing cycle, that is, to improve the printing speed.

1 is a schematic configuration diagram illustrating an inkjet printer according to an embodiment of the present invention. It is a block diagram which shows the structure of the control system of the inkjet printer which concerns on 1st and 2nd embodiment of this invention. It is a graph which shows an example about the kind of drive waveform which concerns on 1st and 2nd embodiment of this invention. FIG. 4A is a graph showing the relationship between the resting time and the dropping speed of the ink droplets ejected first after the resting time when water-based pigment ink is used, and FIG. 4B shows a predetermined condition. FIG. 6 is a graph showing the relationship between the dropping speed and the amount of landing position deviation of the ink droplet from the ideal landing position on the recording paper. FIG. 5 is a graph showing the relationship between the resting time and the landing position deviation amount of the ink droplets ejected first after the resting time based on the relationship between FIG. 4 (A) and FIG. 4 (B). FIG. 6 is an explanatory diagram illustrating a relationship between parameters when printing is performed by relatively scanning a recording head and a recording sheet. FIG. 5 is a diagram illustrating a recording area for recording on a sheet on a recording sheet conveyance belt facing a recording head (A4 longitudinal width) and a preliminary ejection area for performing preliminary ejection. FIG. 8A is a graph showing an example of a method for classifying the discharge amount required for the preliminary discharge in the preliminary discharge region, and FIG. 8B is a graph showing each dotted line region shown in FIG. It is a graph which shows a required preliminary discharge amount based on the experimental result in the worst condition. It is a sequence diagram which shows the flow of the experiment performed in order to obtain | require required preliminary | backup discharge amount. FIG. 6 is a diagram illustrating a state in which a preliminary ejection pulse is set with respect to a preliminary ejection amount at the time of preliminary ejection according to a ejection amount and a pause time in a recording region. It is a block diagram for demonstrating the definition of the idle time which concerns on embodiment of this invention. It is a block diagram for demonstrating the timing which performs preliminary discharge which concerns on 1st Embodiment of this invention. 3 is a flowchart illustrating an example of a process for controlling preliminary ejection in the inkjet printer according to the first embodiment of the present invention. FIG. 6 is a diagram illustrating a state in which a preliminary discharge droplet type is set with respect to a preliminary discharge amount during preliminary discharge according to a discharge amount and a pause time in a recording region. It is a graph which shows an example about the kind of drive waveform which concerns on 3rd Embodiment of this invention. The figure which shows the state which set the preliminary discharge droplet type as larger than the droplet type of the recording region, and set the number of preliminary discharges smaller with respect to the preliminary discharge amount at the preliminary discharge according to the discharge amount and the pause time in the recording region It is.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Inkjet printer 12 Paper supply part 14 Recording head part 18 Maintenance part 20 Recording part 22 Discharge part 24 Paper feed part 26 Conveyor device 28 Loop formation part 30 Guide member 32 Paper discharge belt 34 Paper discharge part 36 Paper conveyance path 38 Star wheel 40 Conveying roll 42 Inkjet recording unit 44 Maintenance device 46 Recording head 48 Temperature sensor 50 Humidity sensor

Claims (13)

A discharge means having a plurality of nozzles for discharging droplets;
The timing at which droplets are finally ejected in the preliminary ejection area set with a pause period in which ejection of liquid droplets is suspended after the image forming area, and the image forming area set after the preliminary ejection area. The interval between the start position and the start position is equal to or less than the maximum value of the droplet discharge interval that can prevent the landing position deviation of the droplet caused by the thickening of the droplet in the image forming region. Timing determining means for determining the start timing of preliminary ejection for each nozzle based on the number of ejections of droplets ejected from each nozzle in the preliminary ejection region;
In the image forming area, droplets based on image data are ejected from the nozzles, and in the preliminary ejection area, droplet ejection is performed in accordance with the number of ejections at the preliminary ejection start timing determined by the timing determination unit. Control means for controlling the discharge means so that is started for each nozzle;
An image forming apparatus.   The image forming apparatus according to claim 1, wherein the number of droplets ejected from each nozzle in the preliminary ejection region is determined according to the total ejection amount of the image forming region and the length of the pause period.   The preliminary ejection area and the image forming area after the preliminary ejection area are provided adjacent to each other, and the timing of the last ejection of the liquid droplets is determined according to the timing of the last liquid ejection in the preliminary ejection area. The image forming apparatus according to claim 1, wherein the timing of landing at a position closest to a start position of an image forming area adjacent to the area is set. Further comprising a detecting means for detecting a physical quantity of at least one of temperature and humidity of the environment in which the discharging means is provided,
The timing determination means determines a preliminary discharge start timing for each nozzle based on the physical quantity and the number of droplets discharged from each nozzle in the preliminary discharge region. The image forming apparatus described in the item.   In the preliminary ejection region, the control means is configured such that the ejection amount per unit number of droplets ejected from each nozzle in the preliminary ejection region or the number of ejection times per unit time corresponds to the number of droplets ejected from each nozzle in the image forming region 5. The image forming apparatus according to claim 1, wherein the discharge unit is controlled so as to be equal to or greater than a discharge amount or a number of discharges per unit time. A discharge means having a plurality of nozzles for discharging droplets;
The total ejection amount ejected from the ejection means in the preliminary ejection area can prevent the landing position deviation of the liquid droplets caused by the thickening of the liquid droplets in the image forming area set after the preliminary ejection area. A discharge amount determining means for determining a discharge amount per unit number of times in the preliminary discharge region for each nozzle so as to be not less than a minimum possible discharge amount and not more than a predetermined amount greater than the minimum discharge amount;
The droplets based on the image data are ejected from each nozzle in the image forming region, and the droplets having the ejection amount determined by the ejection amount determining means are ejected from each nozzle in the preliminary ejection region. Control means for controlling the discharge means;
An image forming apparatus.   The image forming apparatus according to claim 6, wherein the discharge amount determination unit determines a discharge amount per unit number for each nozzle based on a predetermined number of discharges.   The preliminary ejection region is set with a pause period in which the ejection of droplets is suspended after the image forming region, and the ejection amount per unit number of droplets ejected from each nozzle in the preliminary ejection region is set as the image The image forming apparatus according to claim 6, wherein the image forming apparatus is determined in accordance with a total discharge amount of the formation region and a length of the pause period. Further comprising a detecting means for detecting a physical quantity of at least one of temperature and humidity of the environment in which the discharging means is provided,
The image according to any one of claims 6 to 8, wherein the discharge amount determining means determines a discharge amount per unit number of droplets discharged from each nozzle in the preliminary discharge region based on the physical amount. Forming equipment.   The discharge amount determining means is configured such that a discharge amount per unit number of droplets discharged from each nozzle in the preliminary discharge region is equal to or more than a discharge amount per unit number of droplets discharged from each nozzle in the image forming region. The image forming apparatus according to claim 6, wherein the image forming apparatus is determined so as to be.   The controller is configured so that the number of discharges per unit time of droplets discharged from each nozzle in the preliminary discharge region is equal to or greater than the number of discharges per unit time of droplets discharged from each nozzle in the image forming region. The image forming apparatus according to claim 6, wherein the discharge unit is controlled. Computer
The timing at which droplets are finally ejected in the preliminary ejection area set with a pause period in which ejection of liquid droplets is suspended after the image forming area, and the image forming area set after the preliminary ejection area. The interval between the start position and the start position is equal to or less than the maximum value of the droplet discharge interval that can prevent the landing position deviation of the droplet caused by the thickening of the droplet in the image forming region. Timing determining means for determining the start timing of preliminary ejection for each nozzle based on the number of ejections of droplets ejected from each nozzle that ejects droplets in the preliminary ejection region;
In the image forming area, droplets based on image data are ejected from the nozzles, and in the preliminary ejection area, droplet ejection is performed in accordance with the number of ejections at the preliminary ejection start timing determined by the timing determination unit. Control means for controlling so that is started for each nozzle;
Program to make it function. Computer
The total ejection amount ejected from each nozzle that ejects droplets in the preliminary ejection region is a drop in the landing position of the droplet caused by the thickening of the droplets in the image forming region set after the preliminary ejection region. A discharge amount determining means for determining a discharge amount per unit number of times in the preliminary discharge region for each nozzle so as to be not less than a minimum discharge amount that can be prevented and not more than a predetermined amount greater than the minimum discharge amount; ,
Control is performed so that droplets based on image data are ejected from the nozzles in the image forming area, and droplets of the ejection amount determined by the ejection amount determining means are ejected from the nozzles in the preliminary ejection area. Control means to
Program to make it function.

Images