JP2005238780A - Inkjet system image forming device, and print head adjusting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet system image forming device for which the dropping of an ink is prevented from occurring without using a wasteful ink as much as possible. <P>SOLUTION: When a preparatory discharge is performed, instructions to perform the preparatory discharge are transmitted from a host computer 38 to a preparatory discharge controlling section 69, and power is generated in such a manner that the preparatory discharge controlling section 69 makes a discharge pulse generator 68 driven by the instructions. The generated power is fed to a heater for discharging of respective printing heads 22K, 22C, 22M and 22Y through a printing head controller 54. Approximately simultaneously as the feeding, head temperatures measured by a diode sensor of respective printing heads 22K, 22C, 22M and 22Y are transmitted to the preparatory discharge controlling section 69, and the number of times for the preparatory discharge is determined from the head temperatures. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an inkjet image forming apparatus that forms an image by ejecting ink from a print head onto a recording medium.

  2. Description of the Related Art As an output device for a computer or workstation, an inkjet image forming apparatus that forms an image on a recording medium such as recording paper by discharging ink is known. The inkjet image forming apparatus includes, for example, a print head (recording head) on which a plurality of nozzles for ejecting ink are formed, a carriage mounted with the print head and reciprocating in a predetermined main scanning direction, And a recording medium conveyance device that conveys the recording paper in a direction orthogonal to the direction (recording medium conveyance direction).

  When forming an image on the recording paper, the recording paper being conveyed by the recording medium conveying device is temporarily stopped, and the carriage is reciprocated in the main scanning direction based on the image signal carrying the image information. Ink is ejected from the nozzles, and an image for one band is formed on a portion of the recording paper located in the image forming region facing the nozzle outlet (ink ejection port). Thereafter, the recording paper is transported by the width of one band and stopped, and again, the ink is ejected from the nozzles based on the image signal while reciprocating the carriage in the predetermined direction described above, thereby forming an image of the recording paper. An image is formed in a part newly located in the region. By repeating such an operation, an image is formed on the recording paper.

  As described above, a bubble jet method is known as one of methods for ejecting ink from a plurality of nozzles formed in a print head. In this bubble jet method, each of a plurality of nozzles is provided with a discharge heater to which a voltage is applied. By selectively applying a voltage to these discharge heaters, ink is selectively supplied from the plurality of nozzles. Discharge.

  By the way, the image quality is improved in the ink jet type image forming apparatus due to the above-described high-definition nozzles and multi-color ink used. When the nozzles have a higher definition, the number of nozzles formed in the nozzle row increases. Also, the number of nozzles increases when the number of inks is increased. Thus, as the number of nozzles increases, the density of the discharge heaters increases, and the frequency of applying a voltage to the discharge heaters also increases. Therefore, the temperature of each nozzle tends to increase as the resolution of the nozzle increases and the number of colors of ink used increases.

  As described above, when the temperature in the nozzle rises, the bubbles in the nozzle expand and ink droops inadvertently (drops) from the nozzle. In order to prevent such ink dropout, ink is preliminarily ejected during printing or before and after printing. However, since ink is discharged, useless ink is consumed.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an ink jet image forming apparatus and a print head adjustment method that prevent ink from dropping off without using wasted ink as much as possible.

In order to achieve the above object, an inkjet image forming apparatus according to the present invention includes a print head on which a plurality of nozzles for ejecting ink are formed, and performs preliminary ejection for preliminarily ejecting ink from the plurality of nozzles. In an inkjet image forming apparatus for forming an image by ejecting ink from a plurality of nozzles of the print head to a recording medium,
(1) The internal pressure of the print head is adjusted by changing the number of preliminary ejections.

here,
(2) The number of preliminary ejections may be changed based on the temperature in the print head.

Also,
(3) The number of preliminary ejections may be increased as the temperature in the print head is higher.

further,
(4) The number of preliminary ejections may be changed based on the data amount of the image to be formed next.

Furthermore,
(5) The number of preliminary ejections may be increased as the data amount of the next formed image increases.

Furthermore,
(6) The plurality of nozzles of the print head constitute nozzle rows adjacent to each other,
(7) The number of preliminary ejections may be changed based on the temperature of adjacent nozzle rows.

Furthermore,
(8) The number of preliminary ejections may be increased as the temperature of the adjacent nozzle row is higher.

The print head adjustment method of the present invention for achieving the above object includes a print head in which a plurality of nozzles from which ink is ejected is formed, and performs preliminary ejection to preliminarily eject ink from the plurality of nozzles, In a print head adjustment method for adjusting the state of the print head in an inkjet image forming apparatus that forms an image by discharging ink from a plurality of nozzles of the print head to a recording medium,
(9) The condition of the print head is adjusted by adjusting the internal pressure of the print head by changing the number of preliminary ejections.

here,
(10) The state of the print head may be adjusted by changing the number of preliminary ejections based on the temperature in the print head.

Also,
(11) The state of the print head may be adjusted by increasing the number of preliminary ejections as the temperature in the print head increases.

further,
(12) The state of the print head may be adjusted by changing the number of preliminary ejections based on the data amount of the image to be formed next.

Furthermore,
(13) The state of the print head may be adjusted by increasing the number of preliminary ejections as the data amount of the image to be formed next increases.

Furthermore,
(14) The plurality of nozzles of the print head constitute nozzle rows adjacent to each other,
(15) The state of the print head may be adjusted by changing the number of preliminary ejections based on the temperature of adjacent nozzle rows.

Furthermore,
(16) The state of the print head may be adjusted by increasing the number of preliminary ejections as the temperature of the adjacent nozzle row is higher.

  In the inkjet image forming apparatus of the present invention, the internal pressure of the print head is adjusted by changing the number of preliminary discharges. For example, when the internal pressure of the print head is high, the number of preliminary discharges is increased to decrease the internal pressure. It is done. For this reason, it is possible to prevent ink from dripping from the nozzles due to an increase in the internal pressure of the print head. Further, since the number of preliminary ejections is increased / decreased according to the level of the internal pressure of the print head, it is possible to avoid wasted ink as much as possible.

  Further, in the print head adjustment method of the present invention, the internal pressure of the print head is adjusted by changing the number of preliminary discharges to adjust the state of the print head. For example, if the internal pressure of the print head is high, The internal pressure can be lowered by increasing the number of discharges. For this reason, it is possible to prevent ink from dripping from the nozzles due to an increase in the internal pressure of the print head. Further, since the number of preliminary ejections is increased / decreased according to the level of the internal pressure of the print head, it is possible to avoid wasted ink as much as possible.

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

  With reference to FIG. 1, an inkjet plotter as an example of the inkjet image forming apparatus of the present invention will be described.

  FIG. 1 is a perspective view showing a schematic configuration of an ink jet type plotter.

  The plotter 10 includes a platen 14 on which the recording paper 12 conveyed in the direction of arrow A is placed. Two scanning rails (guide rails) 16 are spanned above the platen 14 in parallel to the platen 14. The scanning rail 16 is reciprocated (scanned) in the directions of arrows B and C (a direction orthogonal to the direction of arrow A and an example of the main scanning direction) by a motor (not shown) and an endless belt 18. A carriage 20 is attached via a slide bearing (not shown).

  On the carriage 20, four print heads 22K (black), 22C (cyan), 22M (magenta), and 22Y (yellow) having a plurality of nozzles for ejecting ink are mounted. In front of the nozzle outlet (exit) is an image forming region 23 where an image is formed. Ink is ejected from the nozzles to a portion of the recording paper 12 that is located in the image forming area 23, whereby an image is formed in this portion.

  In the print head 22K, a plurality of nozzles for ejecting black ink are formed in a linear or staggered pattern. In the print head 22C, a plurality of nozzles that discharge cyan ink are formed in a linear or staggered pattern. In the print head 22M, a plurality of nozzles that eject magenta ink are formed in a linear or staggered pattern. In the print head 22Y, a plurality of nozzles for discharging yellow ink are formed in a line in a straight line or a staggered pattern. Each of the print heads 22K, 22C, 22M, and 22Y is formed with a diode sensor (not shown) that measures the temperature of each nozzle row, and each nozzle row is sent from the diode sensor to a preliminary ejection control unit 69 described later. Temperature is sent. In addition, the preliminary ejection conventionally means that ink is preliminarily ejected from each nozzle in order to discharge ink thickened in the nozzle. In addition, in the present invention, ink from each nozzle is used. In order to prevent the ink from dropping or the like, the preliminary discharge includes discharging ink from each nozzle during printing or before and after printing to reduce the amount of ink in the liquid chamber and canceling the increase in internal pressure.

  In addition, ink is forcibly sucked from the nozzles at positions away from the image forming area 23 in the movable range of the carriage 20, and ink supply paths and nozzles formed in the print heads 22K, 22C, 22M, and 22Y. A recovery device 30 is arranged for cleaning the ink etc. to change the ink discharge state of the print heads 22K, 22C, 22M, 22Y to the initial discharge state.

  The recovery device 30 includes four rubber caps 32K, 32C, 32M, and 32Y that cover the ink discharge ports of the four print heads 22K, 22C, 22M, and 22Y. One end of a waste ink tube (not shown) is connected to each cap 32K, 32C, 32M, 32Y, and the other end of the waste ink tube is connected to a suction pump (not shown). The four caps 32K, 32C, 32M, and 32Y are fixed to the cap base 32. The caps 32K, 32C, 32M, and 32Y are also used as ink receivers when the ink thickened by drying at each nozzle is preliminarily ejected and discarded.

  In forming an image on the recording paper 12 such as roll paper, the recording paper 12 was placed on the platen 14 and a part of the outer peripheral surface was exposed from an opening (not shown) formed in the platen 14. The recording paper 12 is conveyed by rotating the conveying roller 24 by the conveying motor 36 (see FIG. 2) while the recording paper 12 is sandwiched between the conveying roller 24 and the pinch roller 26 that presses both ends of the recording paper 12 from above. . The carriage 20 is reciprocated in the directions of arrows B and C above the recording paper 12. Each of the plurality of nozzles formed in each of the print heads 22K, 22C, 22M, and 22Y is formed with a discharge heater (not shown) for discharging ink from each nozzle. The print head controller 54 described later applies the print heads 22K, 22C, 22M, and 22Y so as to apply a voltage to the discharge heater selected from the plurality of discharge heaters based on the image data for a predetermined time (voltage pulse). To control. As a result, ink is ejected from the print heads 22K, 22C, 22M, and 22Y based on the image data, and an image is formed on the portion of the recording paper 12 that is positioned in the image forming area 23.

  When the image formation is completed, a cutter (not shown) mounted on the carriage 20 is ejected to a predetermined position, and the recording paper 12 is cut into a predetermined size. During the image forming operation, the carriage 20 is moved above the recovery device 30 when it is necessary to suck ink from the nozzles in order to clean the nozzles.

  The controller 50 will be described with reference to FIG.

  FIG. 2 is a block diagram showing the controller.

  The controller 50 (see FIG. 1) includes an image controller 52 that controls print data (image data) that carries image information, an engine controller 60 that controls the conveyance of the recording paper 12, the movement of the carriage 20, and the like. The print head controller 54 controls the discharge signals of ink discharged from the heads 22K, 22C, 22M, and 22Y.

  The engine controller 60 includes a data rasterization unit 62 that divides print data sent from the image controller 52, a print parameter change unit 64 that changes print parameters according to the type and output quality of recording paper, and a transport roller 24. A transport control unit 66 that controls the transport motor 36 to be rotated, a discharge pulse generator 68 that generates power to be supplied to a discharge heater disposed in the vicinity of the ink discharge ports of each of the plurality of nozzles, and the four nozzle arrays described above. Of these nozzles, the preliminary ejection control unit 69 that changes how the preliminary ejection is performed based on the diode sensor and sends the change result to the ejection pulse generator 68 is configured.

  Various print data and the like are sent to the image controller 52 from the host computer 38 having a large number of memories. These various print data and the like are sent to the data rasterization unit 62, which divides the print data according to the nozzle widths of the print heads 22K, 22C, 22M, 22Y and the number of print passes. The electric power generated by the discharge pulse generator 68 is controlled by the print head controller 54 and selectively supplied to the discharge heaters of the nozzles. A signal for preliminary ejection from each nozzle is sent from the host computer 38 to the preliminary ejection control unit 69 at a predetermined timing such as after the end of printing. When this signal is sent to the preliminary ejection control unit 69, preliminary ejection is performed as described later.

  The structure of the print head will be described with reference to FIGS.

  FIG. 3 is a schematic diagram showing the inside of the print head. FIG. 4 is a schematic diagram showing a print head in which bubbles are generated in the common liquid chamber. FIG. 5 is a schematic diagram showing a print head in which bubbles expanded due to a temperature rise are formed.

  In each of the print heads 22K, 22C, 22M, and 22Y (here, the print head 22K is shown as an example, but the other print heads 22C, 22M, and 22Y have the same structure), as described above, black ink is used. A plurality of nozzles 22Ka for discharging the gas is formed in a straight line shape or a zigzag shape. Further, a common liquid chamber 22Kb in which ink to be supplied to the plurality of nozzles 22Ka is stored is formed inside the print head 22K. The common liquid chamber 22Kb is partitioned by a filter 22Kc, and the impurities 19a and bubbles 19b in the common liquid chamber 22Kb are captured by the filter 22Kc.

As the temperature in the print heads 22K, 22C, 22M, and 22Y rises, the temperature of the ink existing in the print heads (the nozzle 22Ka and the common liquid chamber 22Kb) also rises. With such a temperature rise, as shown in FIG. 5, the bubbles 19b in the common liquid chamber 22Kb expand, and the pressure (internal pressure) in the print head 22K rises. Normally, the print heads 22K, 22C, 22M, and 22Y are maintained at a negative pressure (pressure lower than the surroundings). However, when the inside of the print heads 22K, 22C, 22M, and 22Y becomes positive pressure (pressure higher than the surroundings), the orifice surface of the ink formed in each nozzle is broken and ink flows out ( I fall out). Therefore, preliminary ejection is performed by a method to be described later, and the print heads are adjusted so that the ink does not inadvertently flow out from the print heads 22K, 22C, 22M, and 22Y. Three examples of the adjustment of the print head will be described.
(First example)

  In preliminary ejection, ink is ejected a predetermined number of times at a predetermined timing. In the present invention, the ink is discharged by the preliminary discharge and the increase in the internal pressure is offset, so that the ink does not flow out carelessly. However, if the number of ink ejections is too large to offset the increase in internal pressure, useless ink will be consumed. Also, if the number of ink ejections is too small to offset the increase in internal pressure, it will not be possible to prevent ink from dropping.

Therefore, as shown in Table 1, the internal pressure of each of the print heads 22K, 22C, 22M, and 22Y is adjusted by changing the number of times ink is ejected to prevent ink from dropping out. Here, as shown in Table 1, for example, the number of ink ejections is changed based on the temperature of each print head 22K, 22C, 22M, 22Y. The temperatures (head temperatures) of the print heads 22K, 22C, 22M, and 22Y in Table 1 are the temperatures measured by the diode sensors that measure the temperatures of the nozzle rows of the print heads 22K, 22C, 22M, and 22Y. The average value of The contents of Table 1 are stored in the preliminary ejection control unit 69. The contents of Table 2 and Table 3 to be described later are similarly stored in the preliminary ejection control unit 69.

  When the head temperature is 20 ° C. or lower, the bubbles 19b (see FIG. 3) have not grown so much, so the head internal pressure is kept at a negative pressure. Therefore, the number of preliminary ejections (the number of preliminary ejections) is set to 5 times. When the head temperature is low, the ink in the print head can be sufficiently discharged even with such a small number of preliminary ejections. Therefore, it is not necessary to waste ink.

  On the other hand, when the head temperature is 40 ° C. or higher, the bubbles 19b (see FIG. 3) grow considerably large, so that the head internal pressure is close to the positive pressure. Therefore, the number of preliminary ejections (the number of preliminary ejections) was set to 200 times. When the head temperature is high, the number of preliminary ejections is increased in this way to sufficiently discharge the ink in the print head. When the head temperature exceeds 20 ° C. and is 30 ° C. or less, the number of preliminary ejections (the number of preliminary ejections) is 50. When the head temperature exceeds 30 ° C. and is 40 ° C. or less, the number of preliminary ejections (preliminary ejection) The number of shots was 100.

  When preliminary ejection is performed, an instruction to perform preliminary ejection is sent from the host computer 38 (see FIG. 2) to the preliminary ejection control unit 69 (see FIG. 2), and the preliminary ejection control unit 69 causes the ejection pulse generator to respond to this instruction. 68 is driven to generate electric power, and the generated electric power is supplied to the discharge heaters of the print heads 22K, 22C, 22M, and 22Y via the print head controller 54. Almost simultaneously with this supply, the head temperatures measured by the diode sensors of the print heads 22K, 22C, 22M, and 22Y are sent to the preliminary discharge controller 69, and the number of preliminary discharges is determined based on the contents of Table 1. .

As described above, when the head temperature is low, the number of preliminary ejections is decreased. On the other hand, when the head temperature is high, the number of preliminary ejections is increased, so that ink is not wasted and ink drops. Can be reliably prevented.
(Second example)

In the second example, as shown in Table 2, the number of preliminary ejections is changed based on the data amount (print duty (%)) of the image to be formed next. This change shows how much the number of preliminary ejections shown in Table 1 has increased or decreased.

  When the print duty of the image to be formed next is large (for example, when it exceeds 25%), a large amount of ink is ejected from each nozzle in the next image formation, and this large amount of ink is discharged. Become. Further, since new ink is supplied to the nozzles, the discharge heater is also cooled, so that an increase in the temperature of the print head can be suppressed. Therefore, when the print duty of the image to be formed next is large, the number of preliminary ejections shown in Table 1 is not changed.

  On the other hand, when the print duty of the image to be formed next is small (for example, 10% or less), only a small amount of ink is ejected from each nozzle in the next image formation, so that a small amount of ink is discharged. It becomes. In addition, since the discharge heater is not easily cooled, the temperature of the print head rises. Therefore, when the print duty of the image to be formed next is small, the number of preliminary ejections shown in Table 1 is increased by about 50% (the increase in the number of ejections is 50%). Similarly, when the print duty exceeds 10% and is 25% or less, the number of preliminary ejections shown in Table 1 is increased by about 25%.

  When preliminary ejection is performed, an instruction to perform preliminary ejection and a print duty are sent from the host computer 38 (see FIG. 2) to the preliminary ejection control unit 69 (see FIG. 2). The ejection pulse generator 68 is driven to generate electric power, and the generated electric power is supplied to the ejection heaters of the print heads 22K, 22C, 22M, and 22Y via the print head controller 54. Almost simultaneously with this supply, the head temperature measured by the diode sensors of the print heads 22K, 22C, 22M, and 22Y is sent to the preliminary discharge controller 69, and the number of preliminary discharges is determined based on the contents of Tables 1 and 2. It is determined.

As described above, by changing the number of preliminary ejections based not only on the head temperature but also on the print duty, it is possible to prevent the ink from being consumed more wastefully and to prevent the ink from dropping out more reliably.
(Third example)

In the third example, as shown in Table 3, based on the temperature of the nozzle row (for example, the nozzle row of the print head 22C) adjacent to the nozzle row (for example, the nozzle row of the print head 22K), the spare nozzles of all the nozzle rows are reserved. Change the number of discharges. This change shows how much the number of preliminary discharges shown in Table 1 has increased or decreased.

  In an inkjet image forming apparatus (inkjet recording apparatus) that performs multicolor printing like the plotter 10 described above, the same number of nozzle rows as the number of ink colors to be used are formed on the print head. When printing is performed with a plurality of nozzle rows, even if the nozzle row is not ejecting ink or the ink ejection frequency is low (low frequency nozzle row), when ink is ejected at a high frequency in adjacent nozzle rows, Since heat is conducted from the nozzle row that ejects ink frequently to the low-frequency nozzle row, the head temperature of the low-frequency nozzle row rises. In such a case, in the low frequency nozzle row, the decrease in the internal pressure of the head due to the ink discharge is small, so that the internal pressure further increases compared to the case where the temperature rises due to the ink discharge of the low frequency nozzle row itself. Dropping easily occurs. Therefore, as shown in Table 3, the number of preliminary ejections of the nozzle rows is adjusted based on the temperature difference between the adjacent nozzle rows. This makes it difficult for the bubbles 19b in the common liquid chamber 22Kb (see FIG. 3) to expand, thereby preventing ink from dropping from each nozzle.

  When the temperature difference between the nozzle row (for example, the nozzle row of the print head 22M) adjacent to the nozzle row (for example, the nozzle row of the print head 22C) and the nozzle row exceeds 20 ° C., the head temperature of the nozzle row increases. Therefore, the number of preliminary discharges shown in Table 1 is increased by about 50% (the increase in the number of discharges is 50%). On the other hand, when the temperature difference between the nozzle row adjacent to the nozzle row and the nozzle row is 10 ° C. or less, the head temperature of the nozzle row has hardly increased, so the number of preliminary ejections shown in Table 1 is changed. No (the increase in the number of shots is 0%). Further, when the temperature difference between the nozzle row adjacent to the nozzle row and the nozzle row exceeds 10 ° C. and is equal to or lower than 20 ° C., the head temperature of the nozzle row is slightly increased. Increase the number of vomiting by about 25% (the increase in the number of shots is 25%).

  When preliminary ejection is performed, an instruction to perform preliminary ejection is sent from the host computer 38 (see FIG. 2) to the preliminary ejection control unit 69 (see FIG. 2), and the preliminary ejection control unit 69 causes the ejection pulse generator to respond to this instruction. 68 is driven to generate electric power, and the generated electric power is supplied to the discharge heaters of the print heads 22K, 22C, 22M, and 22Y via the print head controller 54. Almost simultaneously with this supply, the head temperatures measured by the diode sensors of the print heads 22K, 22C, 22M, and 22Y are sent to the preliminary ejection control unit 69, and the preliminary ejection control unit 69 detects the temperatures of the nozzle rows adjacent to each other. The difference is calculated, and the number of preliminary ejections is determined based on the contents of Tables 1 and 3.

  As described above, by changing the number of preliminary ejections based not only on the head temperature but also on the temperature difference between adjacent nozzle rows, it is possible to eliminate wasteful consumption of ink and more reliably prevent ink from dropping. Can be prevented.

It is a perspective view which shows schematic structure of the inkjet type plotter. It is a block diagram which shows a controller. It is a schematic diagram which shows the inside of a print head. It is a schematic diagram showing a print head in which bubbles are generated in a common liquid chamber. FIG. 3 is a schematic diagram illustrating a print head in which bubbles that have expanded due to a temperature rise are formed.

Explanation of symbols

10 Plotter 22K, 22C, 22M, 22Y Print head 22Ka Nozzle 69 Preliminary discharge controller

Claims (14)

A print head having a plurality of nozzles for discharging ink is provided, and preliminary discharge for discharging ink from the plurality of nozzles is performed in advance, and ink is discharged from a plurality of nozzles of the print head onto a recording medium. In an inkjet image forming apparatus for forming an image,
An ink jet type image forming apparatus, wherein an internal pressure of the print head is adjusted by changing the number of times of the preliminary ejection. The inkjet image forming apparatus according to claim 1, wherein the number of preliminary ejections is changed based on a temperature in the print head. The inkjet image forming apparatus according to claim 2, wherein the number of preliminary ejections is increased as the temperature in the print head is higher. The inkjet image forming apparatus according to claim 1, wherein the number of preliminary ejections is changed based on a data amount of an image to be formed next. The inkjet image forming apparatus according to claim 4, wherein the number of preliminary ejections is increased as the amount of image data to be formed next increases. The plurality of nozzles of the print head constitute nozzle rows adjacent to each other,
The inkjet image forming apparatus according to claim 1, wherein the number of preliminary ejections is changed based on a temperature of adjacent nozzle rows. The inkjet image forming apparatus according to claim 6, wherein the number of times of the preliminary ejection is increased as the temperature of the adjacent nozzle row is higher. A print head having a plurality of nozzles for discharging ink is provided, and preliminary discharge for discharging ink from the plurality of nozzles is performed in advance, and ink is discharged from a plurality of nozzles of the print head onto a recording medium. In a print head adjustment method for adjusting the state of the print head in an inkjet image forming apparatus for forming an image,
A method of adjusting a print head, comprising adjusting the internal pressure of the print head by changing the number of preliminary ejections to adjust the state of the print head. 9. The print head adjustment method according to claim 8, wherein the state of the print head is adjusted by changing the number of times of the preliminary ejection based on the temperature in the print head. 10. The print head adjustment method according to claim 9, wherein the state of the print head is adjusted by increasing the number of preliminary ejections as the temperature in the print head is higher. 9. The print head adjustment method according to claim 8, wherein the state of the print head is adjusted by changing the number of times of the preliminary ejection based on a data amount of an image to be formed next. 12. The print head adjustment method according to claim 11, wherein the state of the print head is adjusted by increasing the number of preliminary ejections as the amount of data of an image to be formed next increases. The plurality of nozzles of the print head constitute nozzle rows adjacent to each other,
The print head adjustment method according to claim 8, wherein the state of the print head is adjusted by changing the number of times of the preliminary ejection based on the temperature of adjacent nozzle rows. The print head adjustment method according to claim 13, wherein the state of the print head is adjusted by increasing the number of times of the preliminary ejection as the temperature of the adjacent nozzle row is higher.

Images