JP2011148287A - Image forming apparatus - Google Patents

Abstract

An undershoot, an overshoot, and a rise / fall delay caused by fluctuations in drive voltage generated according to the number of nozzle holes ejected simultaneously from a recording head are appropriately and quickly suppressed.
When an image data signal is input to the image data count circuit 26b and the image data signal is in an “ink droplet ejection” pattern, 1 count is assumed, and when counting for one nozzle hole row 10Y is completed, The count number is input to the drive waveform control unit 26c. The drive waveform controller 26 refers to the timing correction table 26d according to the number of nozzle holes (actuators 10Y1 to 10YN) that simultaneously eject ink droplets in one nozzle hole array 10Y counted by the image data count circuit 26b. The timing time of the drive waveform voltage applied to the corresponding actuators 10Y1 to 10YN is corrected.
[Selection] Figure 5

Description

  The present invention relates to an image forming apparatus that forms an image by ejecting ink droplets using a piezoelectric element, and particularly to maintain good image quality even when the voltage applied to the piezoelectric element of a recording head fluctuates. The present invention relates to a possible ink jet recording apparatus.

  In an ink jet recording apparatus used as an image forming apparatus such as a printer, a facsimile machine, and a copying machine, a recording head used therefor includes a nozzle hole for ejecting ink droplets, an ink chamber in which the nozzle hole communicates, and the ink chamber And a piezoelectric element that reduces the volume of the ink. The piezoelectric chamber is deformed by applying a pulse voltage generated according to the recorded image from the pulse voltage generating means to the piezoelectric element, and the ink in the ink chamber is ejected from the nozzle hole to form a recording dot on the recording medium. The desired image is formed by forming.

  A piezoelectric element used in such an ink jet recording apparatus has a large capacitor capacity, and when a few hundred dots are applied at a time, a large current flows and a high voltage requires a large driver circuit. However, it is unreasonable to mount a large driver circuit on a print head that scans at high speed, so it is common to have a driver circuit outside the print head and supply drive voltage via a harness (signal path). is there. However, in order to supply a large current to the piezoelectric element through a long path using a harness, the inductance component in the harness increases, resulting in a large delay in undershoot, overshoot, and rise / fall. There was a problem that caused deterioration. In addition, undershoot, overshoot, and rise / fall delays may occur due to temperature changes during use. To solve these problems, the drive waveform applied to the printhead is optimal. Attempts have been made.

  For example, in Patent Document 1, a piezoelectric element driving voltage waveform is adjusted in accordance with variations in the constants and piezoelectric element capacities of each element of the piezoelectric element driving circuit due to changes in the environment temperature of the device, thereby obtaining a stable print quality. A method has been proposed. For this purpose, the piezoelectric element drive voltage of the recording head is measured by the drive voltage measurement unit, analog / digital converted by the analog / digital conversion unit, and read by the voltage control unit. Then, the voltage control unit inputs a value that matches the piezoelectric element driving voltage to a predetermined voltage to the variable voltage source, and the variable voltage source inputs a value corresponding to the value to the voltage waveform forming output unit. Stable print quality can be obtained by inputting an appropriate driving voltage for driving the piezoelectric element from the waveform forming output unit to the recording head. However, in this method, since the drive voltage is not controlled according to the number of nozzle holes ejected simultaneously from the recording head, the occurrence of undershoot, overshoot, and rise / fall delay cannot be sufficiently suppressed. .

  Japanese Patent Laid-Open No. 2004-228688 can simplify the adjustment work of the landing position deviation of the ink droplets in both the forward path and the return path for each of a plurality of recording modes, and can reduce the troublesomeness of the user. An ink jet recording apparatus that outputs a quality print has been proposed. In this method, a chart for adjusting the landing position in which dots are recorded by ejecting ink droplets from a plurality of nozzle holes in the forward and backward movement of the recording head is determined by the user using this chart. Based on the adjustment value of the landing position, the ink landing position of at least one of the forward path and the return path of the recording head is adjusted by the landing position adjusting means.

  However, in this method, although the drive voltage is adjusted according to the number of nozzle holes discharged simultaneously from the recording head, a chart for adjusting the landing position in which dots are recorded by discharging ink droplets from a plurality of nozzle holes, Since the user sets the adjustment value, it takes time to set the adjustment value, and there is a stagnation that lacks quickness.

  The present invention has been made in consideration of the above-described circumstances, and causes the occurrence of undershoot, overshoot, and rise / fall delay due to fluctuations in the drive voltage generated according to the number of nozzle holes ejected simultaneously from the recording head. An object of the present invention is to provide an image forming apparatus capable of being appropriately and quickly suppressed.

  In order to solve the above problems, the invention described in claim 1 is a recording head having a nozzle hole array in which a plurality of nozzle holes for ejecting ink droplets are arranged by driving a piezoelectric element, and driving the piezoelectric element of the recording head. A recording head driving unit that feeds an image data signal and a driving waveform output signal that drives a piezoelectric element of the recording head in accordance with the image data signal to the recording head driving unit, from the nozzle hole of the recording head In the image forming apparatus including the recording head control unit that controls the ejection of the ink droplets, the recording head control unit simultaneously counts the number of nozzle holes that eject ink droplets from the image data signal, and an image A first correction sensor storing a correction amount of the output timing of the drive waveform output signal for driving the piezoelectric element corresponding to the number of nozzle holes counted by the data counting means. And Bull, the output timing based on the first correction table is obtained by a delivering a drive waveform output signal to the recording head drive unit driving waveform control section.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the recording head control unit stores the correction amount of the output timing of the drive waveform output signal according to the type of the waveform of the drive waveform output signal. The drive waveform control unit includes a second correction table, and sends a drive waveform output signal to the recording head drive unit at an output timing based on the first and second correction tables.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the recording head has a plurality of nozzle hole arrays, and ink droplets are ejected by the recording head controller for each nozzle hole array. Is controlled.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the recording head has a nozzle hole array for ejecting different color ink droplets, and the different color ink droplets are ejected. The ejection of ink droplets is controlled by the recording head controller for each nozzle hole array to be ejected.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the recording head is mounted so as to be able to reciprocate in the main scanning direction. The reciprocation correction table for correcting the output timing of the ink is provided in the recording head controller, and the reciprocation correction table can be used to change the ejection timing of the ink droplets from the nozzle holes of the recording head between the forward path and the return path. Is.

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the recording head scans in the main scanning direction and forms an image by ejecting ink droplets from the nozzle holes. In this case, the recording head control unit is provided with a print start timing adjusting means for adjusting the print start timing of the drive waveform output signal every time at least one scan is performed, and the print start timing adjustment is performed every time one scan is performed. By using the means, it is possible to change the ejection start timing of the ink droplets from the nozzle holes of the recording head.

  According to the present invention, an image capable of appropriately and quickly suppressing the occurrence of undershoot, overshoot, and rise / fall delay due to fluctuations in drive voltage generated according to the number of nozzles ejected simultaneously from the recording head. A forming apparatus can be provided.

1 is a plan view showing a schematic configuration of a main part of an ink jet recording apparatus according to an embodiment of the present invention. It is a figure which shows the functional block of the principal part of the inkjet recording device shown in FIG. FIG. 3 is a detailed block diagram of a recording head control unit and a recording head driving unit shown in FIG. 2. FIG. 4 is a signal timing diagram of the recording head control unit and the recording head driving unit shown in FIG. 3. FIG. 2 is a block circuit diagram of a recording head control unit according to the first embodiment of the invention. FIG. 6 is a detailed block diagram of an image data count circuit in the recording head controller shown in FIG. 5. FIG. 6 is a signal timing diagram illustrating correction of the timing of the drive waveform output signal by the recording head controller shown in FIG. 5. FIG. 6 is a flowchart for performing timing correction processing of a drive waveform output signal by the recording head controller shown in FIG. 5. FIG. 6 is a table of a correction table stored in the recording head controller shown in FIG. FIG. 3 is a block diagram for explaining a recording head control unit corresponding to each color of the recording head control unit according to the first embodiment of the present invention. FIG. 11 is a table showing a correction table for each color stored in a recording head controller corresponding to each color shown in FIG. 10. 1 is a configuration example of an image forming system according to an embodiment of the present invention. It is a block diagram which shows schematic structure of the personal computer shown in FIG. It is a block diagram of a recording head control unit of a modification of the ink jet recording apparatus according to the first embodiment of the present invention. It is a table | surface figure which shows the specific example of the correction table for reciprocation stored in the recording head control part which concerns on 2nd Embodiment by this invention. FIG. 16 is a flowchart for correcting the landing positions of ink droplets using the reciprocation correction table shown in FIG. 15. 6 is a plan view of an original data image showing diagonal lines formed along a sub-scanning direction B. FIG. It is a top view which shows the oblique line image which shows the shift | offset | difference for every scan. FIG. 10 is a functional block diagram of a recording head control unit according to a third embodiment. It is a figure which shows an example of drive waveform information. 10 is a flowchart illustrating an example of a drive waveform output signal correction process according to the third embodiment. It is a figure which shows an example of the correction table in 3rd Embodiment. FIG. 10 is another example of a functional block diagram of a recording head control unit in the third embodiment. It is a figure which shows the other example of the correction table in 3rd Embodiment. It is a figure which shows the correction table for reciprocation in 3rd Embodiment. 14 is a flowchart illustrating another example of a drive waveform output signal correction process according to the third embodiment.

  Hereinafter, an embodiment for carrying out the present invention will be described in detail with reference to the drawings. First, an ink jet recording apparatus that is an image forming apparatus according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a plan view showing a schematic configuration of a main part of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing functional blocks of the main part of the ink jet recording apparatus shown in FIG. FIG. 3 is a detailed block diagram of the recording head control unit and the recording head driving unit shown in FIG. FIG. 4 is a signal timing chart of the recording head control unit and the recording head driving unit shown in FIG.

(Configuration of image forming apparatus)
An ink jet recording apparatus according to an embodiment of the present invention includes a carriage 1 having recording heads 9A and 9B that move in the direction of arrow A, which is the main scanning direction, and eject ink droplets onto the surface of a recording medium P such as paper. I have. The carriage 1 is held and guided by a guide rod 2 and attached so as to be able to reciprocate in the direction of arrow A. Further, the carriage 1 is connected to an endless timing belt 4 stretched by a pulley 11 attached to a rotation shaft of the main scanning motor 3 and a pulley 12a attached to a support shaft 12 of the apparatus main body at a connecting portion 1a. It is attached. As the main scanning motor 3 rotates, the timing belt 4 is moved in the direction of arrow A, and the carriage 1 is also moved in the direction of arrow A at a predetermined speed. In order to detect the transport amount of the carriage 1 in the direction of arrow A, a main scanning encoder sheet 5 having a pattern recorded at equal intervals is attached in parallel along the guide rod 2. This pattern can be detected by the main scanning encoder sensor 6 attached to the carriage 1 so that the position of the carriage 1 in the main scanning direction can be detected.

  On the other hand, the recording medium P is electrostatically adsorbed and held on an endless conveyance belt 15 stretched between the support shaft 14 and the rotation shaft 13, and the conveyance belt 15 moves in the direction of arrow B (sub-scanning direction). Along with the transfer, it is transferred in the B direction. The conveyance belt 15 is arranged in the direction of arrow B by an endless timing belt 18 stretched between a pulley 16 attached to the rotation shaft of the sub-scanning motor 7 and a pulley 17 attached to the rotation shaft 13 of the conveyance belt 15. Is rotated and transported. That is, with the rotation of the sub-scanning motor 7, the timing belt 18 is rotated and transferred, and the pulley 17 attached to the rotating shaft 13 is rotated and the rotating shaft 13 is driven to rotate together with the rotation and transfer of the timing belt 18. The transport belt 15 is transferred in the direction of arrow B along with the driving rotation of the rotary shaft 13. Further, a sub-scanning encoder disk 19 marked at equal intervals in the circumferential direction is attached to the end of the rotating shaft 13. The marking of the encoder disk 19 is detected and the B direction of the recording medium P is detected. A sub-scanning encoder sensor 20 for detecting the amount of transfer to is attached.

  In the recording heads 9A and 9B, a plurality of nozzle holes 10 for ejecting ink droplets toward the recording medium P are arranged in two rows in the main scanning direction, and each nozzle hole row 10Y. Yellow, cyan, magenta, and black ink droplets are ejected from 10C, 10M, and 10K, respectively. The nozzle hole arrays 10Y, 10C, 10M, and 10K are arranged in the nozzle hole arrays 10Y, 10C, 10M, and 10K by vibrations of the piezoelectric elements to which a drive voltage is applied, as will be described later. Ink droplets are ejected from the nozzle holes 10.

  In FIG. 1, reference numeral 8 denotes a recovery device for recovering defective ejection of ink droplets from the nozzle holes 10. The recovery device 8 includes a cap unit, a suction unit, and a cleaning unit (not shown). The carriage 1 is moved to the recovery device 8 side during printing standby, and the recording heads 9A and 9B are capped by the capping means, and the ejection port portion is kept in a wet state to prevent ejection failure due to ink liquid drying. Further, by discharging ink liquid not related to recording during recording or the like, the ink liquid viscosity of all the discharge ports is made constant and stable discharge performance is maintained. When a discharge failure occurs, the discharge ports (nozzle holes 10) of the recording heads 9A and 9B are sealed by the capping unit, and bubbles and the like are sucked out from the discharge port by the suction unit through the tube. Ink liquid and dust adhering to the surface are removed by the cleaning means, and the ejection failure is recovered.

  By moving the carriage 1 in the main scanning direction (A direction) and ejecting ink from the recording heads 9A and 9B once, an image is formed on the recording medium P with a band having the same width as the length of the nozzle hole array. Can be formed. When the image formation for one band is completed, the sub-scanning motor 7 is driven to move the recording medium P in the sub-scanning direction (B direction) and repeat the image forming operation for one band again. For example, an image can be formed at an arbitrary location on the recording medium P.

  As shown in FIG. 2, such an image forming process includes a host interface (host I / F) 22 that transmits a signal from a host PC 21 that controls the entire inkjet recording apparatus, a CPU 23 that controls the image forming process, A ROM 24, a RAM 25, a recording head control unit 26, a main scanning control unit 27, and a sub scanning control unit 28 are provided. These functional means are connected by a bus 29, and the CPU 23 controls the exchange of signals of these functional means. Specifically, firmware for controlling the hardware of the inkjet recording apparatus and drive waveform data for driving the recording heads 9A and 9B are stored in the ROM 24. When a print job (image data) is received from the host PC 21, the CPU 23 Stores the image data in the RAM 25. The drive waveform data differs depending on the print mode, and, for example, the waveform rising / falling speed, amplitude, number of pulses, and the like are different.

  On the other hand, the carriage 1 on which the recording heads 9A and 9B are mounted operates the main scanning control unit 27 based on an instruction signal from the CPU 23, obtains a signal supply from the main scanning encoder sensor 6, and stops the carriage 1. The position is recognized, and the main scanning motor 7 is operated to move to an arbitrary position on the recording medium P.

  Further, as will be described later, the recording head control unit 26 including a digital / analog conversion (DA conversion) circuit, a filter circuit, and a signal amplification amplifier circuit is interlocked with the position information of the carriage 1 obtained from the main scanning encoder sensor 6, A drive waveform signal and a control signal based on the image data stored in the RAM 25 and the print head drive waveform data stored in the ROM 24 are transferred to the print head 1 drive unit 30A, the print head 2 drive unit 30B, the print head 3 drive unit 30C, It is fed to the head 4 drive unit 30D. The recording head driving units 30A, 30B, 30C, and 30D are recording heads that mainly eject ink droplets from the nozzle holes of the nozzle hole array 10Y based on the image data and the driving waveform signal supplied from the recording head control unit 26. 91, similarly, a recording head 92 for ejecting ink droplets from the nozzle hole array 10C, a recording head 93 corresponding to the nozzle hole array 10M, and a recording head 4 corresponding to the nozzle hole array 10K, respectively. Is discharged.

  Next, as an example, the relationship between the recording head control unit 26, the recording head driving unit 30A, and the nozzle hole array 10Y of the recording head 1 will be described with reference to FIGS.

  As described above, in the recording head control unit 26 and the recording head driving units 30A, 30B, 30C, and 30D, as shown in FIG. 2, each recording head driving unit 30A, 30B, 30C, Image data and driving waveform signals are supplied to 30D, and the recording heads 91, 92, 93, 94 are operated to eject ink droplets from the nozzle hole arrays 10Y, 10C, 10M, 10K. In this case, the operation relationship between the recording head driving units 30A, 30B, 30C, and 30D by the recording head control unit 26 and the recording heads 91, 92, 93, and 94 is basically the same, and as an example the recording head control unit 26 and the recording head driving unit 30A and the recording head 91 of the recording head 1 will be described with reference to FIG.

  As shown in FIG. 3, the recording head drive unit 30A includes a shift register 31, a latch 32, a gradation decoder 33, a level shifter 34, and an analog switch 35. The recording head 91 includes actuators 10Y1 to 10YN that eject ink droplets from the nozzle holes 10 corresponding to the nozzle holes 10 of the nozzle hole array 10Y. Then, as shown in FIG. 3, the recording head control unit 26 sends the image data SD [1: 0] and the synchronous clock signal SCK to the shift register 31, latch 32, gradation decoder 33, level shifter 34, and analog switch 35, respectively. The gradation signal MN [3: 0] and the drive waveform output signal Vcom sent to the actuators 10Y1 to 10YN corresponding to the nozzle holes 10 are sent.

  As a result, as shown in FIG. 4, the image data is transferred from the recording head control unit 26 to the recording head driving unit 30A by the SD [1: 0] signal and the SCK signal in a serial manner, and the image data SD [ 1: 0] is latched with a predetermined time width. The Vcom signal, together with the gradation signal MN [3: 0] corresponding to the image data SD [1: 0] transferred serially for each nozzle hole 10, is turned on / off by the analog switch 35 to thereby turn the actuators 10Y1 to 10Y1. 10YN. Then, signals of Vout0, Vout1, Vout2, and Vout3 are formed, and “no droplet”, “small droplet”, “medium droplet”, “large droplet” are output according to the outputs of these Vout0, Vout1, Vout2, and Vout3. Are ejected from each nozzle hole 10. In terms of timing, as shown in FIG. 4, after serial image data is transferred with the SCK, SD [1: 0], and LT signals, the Vcom signal and the MN signal are output as a set, and the corresponding actuators 10Y1 to 10YN In operation, ink droplets are ejected from the corresponding nozzle holes 10.

  When the actuators 10Y1 to 10YN are operated by such a recording head control unit 26, the drive waveform output may be distorted by connecting the recording head control unit 26 and the recording head driving unit 30A with a harness. The level differs depending on the number of nozzle holes ejected at the same time, and there is a problem that an abnormal image is generated. As a result of examining this problem, it was found that there are the following causes.

  That is, a control unit such as a CPU sends image data to be written next to the recording head control unit 26. The recording head controller 26 sends drive waveform data for driving the piezoelectric elements in the actuators 10Y1 to 10YN to the DA converter circuit based on the image data. In the DA conversion circuit, the drive waveform data sent from the ROM is converted into an analog voltage and sent as a drive waveform output signal to the signal amplification amplifier circuit through the filter circuit. The amplifier output from this signal amplification amplifier circuit has an ideal waveform without being affected by inductance because it has not passed through the harness. Here, when the number of dots to be written at a time is small (when there are few nozzle holes that simultaneously eject ink droplets), the charging current to the piezoelectric element is small, so the influence of the inductance of the harness is small, and the piezoelectric element drive voltage is almost an amplifier output Will be the same. However, the current increases as the number of dots (number of nozzle holes) written at a time increases, causing undershoot and overshoot due to the inductance of the harness, and the drive voltage waveform of the piezoelectric element is broken. Naturally, this breaking method increases as the current increases. That is, the larger the number of dots written simultaneously, the greater the collapse of the drive voltage waveform of the piezoelectric element. The collapse of the waveform affects the ink discharge speed Vj. If Vj is different from the target, the ink landing position is affected and the image is affected. In particular, this is a serious problem in a printing mode in which printing is performed by bidirectional scanning in a reciprocating motion.

  In the present invention, in order to solve such a problem, the feeding timing timing of the drive waveform output signal is measured in advance according to the number of actuators 10Y1 to 10YN corresponding to the number of nozzle holes that simultaneously eject ink droplets. Correction and adjustment are performed based on the correction data that is present, so that the drive waveform output signal is prevented from collapsing.

(First embodiment)
Such correction and adjustment of the timing for supplying the drive waveform output signal will be described with reference to FIGS. FIG. 5 is a block circuit diagram of the recording head control unit according to the first embodiment of the present invention. FIG. 6 is a detailed block diagram of an image data count circuit (image data count means) in the printhead controller shown in FIG. FIG. 7 is a signal timing diagram illustrating correction of the timing of the drive waveform output signal by the recording head controller shown in FIG. FIG. 8 is a flowchart for correcting the timing of the drive waveform output signal by the recording head controller shown in FIG. FIG. 9 is a table of a correction table (first correction table) stored in the recording head controller shown in FIG.

  As shown in FIG. 5, the recording head control unit 26 according to the first embodiment of the present invention includes an image data control unit 26a, an image data count circuit 26b, a drive waveform control unit 26c, and a timing correction table (first correction table). 26d, a drive waveform shaping unit 26e having a DA conversion circuit, a filter circuit, a signal amplification amplifier circuit, and the like is provided. First, the image data SD [1: 0] is output from the image data control unit 26a. The image data SD [1: 0] output from the image data control unit 26a is supplied to the recording head drive unit 30A via the harness (see FIG. 3) and is also supplied to the image data count circuit 26b. . As shown in FIG. 6, SD [1: 0] image data signal is input to the image data count circuit 26b, and when the image data signal SD [1: 0] is an “ink droplet ejection” pattern, one count is performed. When the count for one nozzle hole array 10Y is completed, the signal is input to the drive waveform controller 26c as a JET_NUM [8: 0] signal.

  The drive waveform controller 26 refers to the timing correction table 26d according to the number of nozzle holes (actuators 10Y1 to 10YN) that simultaneously eject ink droplets in one nozzle hole array 10Y counted by the image data count circuit 26b. The timing time of the drive waveform voltage applied to the corresponding actuators 10Y1 to 10YN is corrected. That is, as shown in FIG. 7, the delay time tD from the end of the LT signal that latches the image data SD [1: 0] (the signal rise in FIG. 7C) is equal to the number of nozzle holes that discharge simultaneously. When the number is large (Vcom1), a short delay time tD1 is set (see FIG. 7D). When the number of nozzle holes ejected simultaneously is small (Vcom2), a long delay time tD2 is set (see FIG. 7E). ). For this correction, for example, as shown in FIG. 9, refer to a correction table 26d showing the relationship between the preset number of nozzle holes to be ejected simultaneously and the delay time tD of the drive waveform output signal corresponding to this number of nozzle holes. Then, the correction delay time tD value automatically determined is applied. Then, the drive waveform output signal Vcom whose timing is corrected in this way passes through the image waveform shaping unit 26e such as a DA conversion circuit, a filter circuit, and a signal amplification amplifier circuit, and drives the recording head 10Y. Is output as In this embodiment, the correction table illustrates an example in which tD is a small value when the number of nozzle holes ejected simultaneously is small, and a large value when the number of nozzle holes ejected simultaneously is small. Since it varies depending on the characteristics of the harness and the actuator, the correction value of the delay time tD of the drive waveform output signal corresponding to the number of nozzle holes discharged simultaneously and the number of nozzle holes in the correction table 26d is measured by measuring these relationships. And may be determined as appropriate.

  Next, a flow of performing the correction process of the drive waveform output signal as described above will be described with reference to FIG. First, when a print command is generated (step S1), image data and a drive waveform are set by software (step S2). At this time, the output timing correction value of the drive waveform is not fixed and is not set by software. Next, printing is started by software (step S3). The image data is output by hardware (step S4), and the number of nozzle holes for simultaneously discharging the output signal by the image data count circuit 26b is counted (step S5). Based on the result, the correction value is determined with reference to the correction table 26d (step S6), and the corrected drive waveform signal is output and input to the head drive unit 30A (step S7). Based on the drive waveform output signal, the actuators 10Y1 to 10YN are operated, and ink droplets are ejected from the corresponding nozzle holes 10 (step S8). By performing such correction processing, appropriate image formation can always be performed promptly regardless of the number of nozzle holes ejected simultaneously.

  Next, in this embodiment, as described above, four color inks of yellow (Y), cyan (C), magenta (M), and black (K) are used as the recording heads 91, 92, 93, 94. In use, ink droplets of corresponding colors are ejected from the respective nozzle hole arrays 10Y, 10C, 10M, and 10K. When an image is formed using such multi-colored inks, the viscosity characteristics are different for each ink color, so that the landing positions of the ink droplets ejected from the nozzle holes may be shifted for each color. For this reason, in this embodiment, the ink droplet ejection timing is adjusted for each color of ink used. The discharge timing for each color will be described with reference to FIGS.

  FIG. 10 is a block diagram for explaining a recording head control unit corresponding to each color of the recording head control unit according to the first embodiment of the present invention. FIG. 11 is a table showing a correction table for each color stored in the recording head controller corresponding to each color shown in FIG.

  The recording head control unit 26 according to the first embodiment performs recording for controlling the actuators 10Y1 to 10YN of the nozzle hole arrays 10Y, 10C, 10M, and 10K that respectively discharge yellow, cyan, magenta, and black ink droplets. Head controllers 26Y, 26C, 26M, and 26K are provided. As shown in FIG. 10, these recording head controllers 26Y, 26C, 26M, and 26K are image data controllers 26aY, 26aC, 26aM, and 26aB, image data count circuits 26bY, 26bC, 26bM, and 26bB, respectively. It has waveform control units 26cY, 26cC, 26cM, 26cB, correction tables 26dY, 26dC, 26dM, 26dB, and drive waveform shaping units 26eY, 26eC, 26eM, 26eB. Therefore, these recording head controllers 26Y, 26C, 26M, and 26K can independently control the ejection of ink droplets from the respective nozzle hole arrays 10Y1 to 10YN. As a result, it is possible to appropriately adjust the difference in landing position that differs for each ink color, and to form a high-quality image.

  FIG. 11 shows specific examples of the correction tables 26dY, 26dC, 26dM, and 26dB stored in the recording head controllers 26Y, 26C, 26M, and 26K. As shown in FIG. 11, corrections corresponding to the respective colors are shown. It is clear that the delay time tD in the table is different with respect to the number of nozzle holes ejected simultaneously.

  In the first embodiment, the case where the recording heads 91, 92, 93, and 94 have one nozzle hole array 10Y, 10C, 10M, and 10K having different ink colors has been described. However, the recording head 91 may have a plurality of nozzle hole rows 10Y1, 10Y2, 10Y3, 10Y4. Even in such a case, it is preferable to adjust the discharge timing at which the plurality of nozzle hole arrays 10Y1, 10Y2, 10Y3, and 10Y4 are independently discharged from each nozzle hole array.

  It is also preferable to configure the image forming system (printing system) by connecting the image forming apparatus according to the present embodiment to a personal computer as an information processing apparatus as shown in FIG. In this embodiment, the image forming system 300 includes a personal computer 301 as an example of an information processing apparatus (host PC) that is a host apparatus that transmits print data and a print job including a print condition for printing the print data. A printer apparatus (printer) 302 as an example of an image forming apparatus that prints print data is connected through a cable 303 as a connection unit.

  The personal computer 301 uses, for example, print data corresponding to the created document and print condition data set for printing the document (paper orientation, duplex, consolidation, bookbinding, staple, punch, enlargement / reduction, etc.) as a print job. The data is sent to the printer device 302.

  On the other hand, the printer apparatus 302 which is the ink jet recording apparatus prints print data in accordance with a print job sent from the personal computer 301. Specifically, the printer device 302 prints the print data included in the print job according to the print condition data included in the print job (for example, paper orientation, double-sided, aggregation, bookbinding, staple, punch, enlargement / reduction, etc.). Print on media such as.

  FIG. 13 is a block diagram illustrating a schematic configuration of a personal computer 301 as an information processing apparatus. The personal computer 301 includes an input unit 310 for inputting data, a display unit 311 such as a display, a communication unit 312 for performing data communication, a CPU 313 as control means for controlling the entire apparatus, A RAM 314 used as a work area, a recording medium drive device 315 that reads / writes data on the recording medium, a recording medium 316 such as a ROM that stores various programs for operating the CPU 313, and the like, and outputs sound And an audio output unit 317.

  The input unit 310 includes a keyboard having cursor keys, numeric input keys, various function keys, and the like, a mouse and a slice pad for selecting keys on the display screen of the display unit 311, and the user operates the CPU 313. This is a user interface for giving instructions and inputting data.

  The display unit 311 includes a CRT, an LCD, or the like, and performs display according to display data input from the CPU 313. The communication unit 312 is for data communication with the outside. For example, the communication unit 312 is for data communication with the printer device 302 or the like via the cable 303.

  The CPU 313 is a central control unit that controls the entire apparatus in accordance with a program stored in the recording medium 316. The CPU 313 includes an input unit 310, a display unit 311, a communication unit 312, a RAM 314, a recording medium drive device 315, and the like. Are connected to control data communication, reading of an application program by accessing a memory, reading / writing of various data, data / command input, display, and the like.

  Further, the CPU 313 sends the print data input from the input unit 310 and the print condition data of the print data to the printer device 302 via the communication unit 312 as a print job.

  The RAM 314 includes a work memory that stores designated programs, input instructions, input data, processing results, and the like, and a display memory that temporarily stores display data to be displayed on the display screen of the display unit 311.

  The recording medium 316 stores various programs and data such as an OS program executable by the CPU 313 (for example, Microsoft operating system Windows (registered trademark) XP), a document creation application program, a printer driver corresponding to the printer device 302, and the like. Store. As the recording medium 316, for example, an optical / magnetic / electric recording medium such as a floppy (registered trademark) disk, a hard disk, a CD-ROM, a DVD-ROM, an MO, or a PC card can be used.

  Various programs are stored in the recording medium 316 in a data format readable by the CPU 313. Various programs may be recorded in advance on the recording medium 316, downloaded via a communication line such as the Internet, and stored in the recording medium 316.

  Control for correcting and adjusting the timing of supplying the drive waveform output signal based on the correction table in accordance with the number of nozzle holes for simultaneously ejecting ink droplets by the ink jet recording apparatus according to the present invention described above is a program (image formation). Program). For example, the image forming program is preferably executed by the recording head control unit 26. For example, it is also preferable that the program is provided by downloading from the Internet and installed from the information processing apparatus 301 to the image forming apparatus 302. Further, the present invention is also applied to a mode of a recording medium (recording medium on which an image forming program is recorded) on which an image forming program is recorded so as to be executable by the image forming apparatus 302.

  FIG. 14 is a block diagram of a recording head controller of a modification of the ink jet recording apparatus according to the first embodiment of the present invention. In the ink jet recording apparatus shown in this modification, in the recording heads 91, 92, 93, 94 shown in the first embodiment, for example, a plurality of nozzle hole arrays 10Y1, 10Y2, 10Y3, 10Y4 are provided in the recording head 91. The recording head control unit in the case of having it is shown. That is, the recording head 91 has four nozzle hole rows 10Y1, 10Y2, 10Y3, and 10Y4. In these four nozzle hole rows 10Y1, 10Y2, 10Y3, and 10Y4, the number of nozzle holes that are ejected simultaneously is determined. In some cases, the landing positions of the ink droplets may be shifted. In the present invention, as described in the first embodiment, the deviation of the landing positions of the ink droplets is independent of the recording head controllers 26Y1, 26Y2 for each of the nozzle hole arrays 10Y1, 10Y2, 10Y3, 10Y4. , 26Y3, and 26Y4, and the ink droplet ejection timing can be adjusted for each of the nozzle hole arrays 10Y1, 10Y2, 10Y3, and 10Y4.

  In order to adjust the ink droplet ejection timing for each nozzle hole array 10Y1, 10Y2, 10Y3, 10Y4 in the recording head controller 26, the recording head controller 26Y1 corresponding to each nozzle hole array 10Y1, 10Y2, 10Y3, 10Y4. , 26Y2, 26Y3, and 26Y4. As shown in FIG. 14, the recording head controllers 26Y1, 26Y2, 26Y3, and 26Y4 include image data controllers 26aY1, 26aY2, 26aY3, and 26aY4, image data count circuits 26bY1, 26bY2, 26bY3, and 26bY4, and drive waveforms. The controller 26cY1, 26cY2, 26cY3, 26cY3, the correction table 26dY1, 26dY2, 26dY3, 26dY4, and the drive waveform shaping unit 26eY1, 26eY2, 26eY3, 26eY4 are provided. Therefore, these recording head controllers 26Y1, 26Y2, 26Y3, and 26Y4 can independently control the ejection of ink droplets from the respective nozzle hole arrays 10Y1 to 10YN. As a result, it is possible to appropriately adjust the deviation of the landing positions for each of the nozzle hole arrays 10Y1, 10Y2, 10Y3, and 10Y4 and form a high-quality image. In this case as well, the ink ejection timing is corrected using the preset correction tables 26dY1, 26dY2, 26dY3, and 26dY4 for each of the recording head controllers 26Y1, 26Y2, 26Y3, and 26Y4, as in the above embodiment. It is like that.

(Second Embodiment)
Next, as a second embodiment according to the present invention, a case where image formation by the recording heads 91, 92, 93, 94 is performed in both the forward and backward paths of the carriage 1 will be described with reference to FIGS. . FIG. 15 is a table showing a specific example of a reciprocation correction table stored in the recording head control unit according to the second embodiment of the present invention. FIG. 16 is a flowchart for correcting the ink droplet landing position using the reciprocation correction table shown in FIG. Note that a description of the same points as in the first embodiment will be omitted.

  When image formation by the recording heads 91, 92, 93, 94 is performed in both the forward path and the backward path of the carriage 1, the ink droplets in the forward path and the backward path are due to differences in the moving speed of the carriage 1 in the forward path and the backward path. There may be a deviation in the landing position. In the second embodiment, the deviation of the landing positions of the ink droplets in the forward path and the return path can be appropriately adjusted. That is, in the second embodiment, the recording head controllers 26Y, 26C, 26M, respectively corresponding to the nozzle hole arrays 10Y, 10C, 10M, and 10K of the recording heads 91, 92, 93, and 94 in the first embodiment. 26K, and the recording head controllers 26Y, 26C, 26M, and 26K are provided with reciprocal correction tables for correcting the timings of the drive waveform output signals in the forward path and the backward path, respectively. FIG. 15 shows, as an example, correction tables 26dYA and 26dYB for reciprocation of the forward path and the backward path in the nozzle hole array 10Y. As can be seen from FIG. 15, it is clear that the delay time tD to be corrected is different for the number of nozzle holes ejected simultaneously in the forward path and the backward path. In this way, by performing different corrections in the forward path and the backward path of the carriage 1, the landing positions of the ink droplets when recording in the forward path and the backward path are corrected, and appropriate image formation becomes possible.

  The image forming process in the forward path and the backward path using such a reciprocation correction table will be described based on the flowchart shown in FIG.

  First, when a print command is generated (step S9), image data and drive waveform are set by software (step S10). At this time, the output timing correction value of the drive waveform is not fixed and is not set by software. Next, printing is started by software (step S11). Image data is output by hardware (step S12), and the number of nozzle holes for simultaneously discharging the output signal is counted by the image data count circuits 26bYA and 26bYB (step S15). In this case, it is determined whether or not the count result is the forward path (step S14). If Yes, the output timing correction value is determined by referring to the forward path correction table 26dYA based on the result (step S14). In step S16, the corrected driving waveform signal is output and input to the head driving unit 30A (step S17). Based on the drive waveform output signal, the actuators 10Y1 to 10YN of the corresponding nozzle hole array are operated, and ink droplets are ejected from the corresponding nozzle holes 10 (step S18). On the other hand, if the number of nozzle holes counted by the image data count circuits 26bYA and 26bYB is determined No in step S14, the return path correction table 26dYB is referred to (step S19). Based on the result of the correction table 26dYB, the output timing is corrected in step 16 to determine the output timing correction value. Thereafter, the drive waveform is output in step S17, and the ink is ejected in step S18.

  Next, as shown in FIG. 17, when the image of the original data is formed with diagonal lines L along the sub-scanning direction B, when the image is formed by scanning the recording head in the main scanning direction A, In some cases, the front end and the end of the oblique line in the sub-scanning direction are deviated for each scanning. That is, as shown in FIG. 18, the scan of the recording head (scanning) is performed by alternately changing the scanning direction from S1 to S5, and the original data image having the oblique line L shown in FIG. When image formation is performed with such an ink jet recording apparatus, an image is formed by shifting the oblique lines L1 to L5 formed for each scan, for example, the end L1b of the oblique line L1 and the start end L2a of the oblique line L2 formed in the next scan, It may be different from the original data image.

  In the present invention, it is possible to correct the deviation between the end and the start of the oblique lines L1 to L5. That is, since the printing timing is performed by the LT signal and the Vcom signal shown in FIG. 3, the deviation can be corrected by adjusting the output timing of the LT signal and the Vcom signal and adjusting the Vout signal at the same time. It becomes. First, since the image is designed on the assumption that no delay occurs at the time of ejection, it is examined how much delay has occurred by introducing the method of the second embodiment. In the method of the second embodiment, as shown in FIG. 13, a delay when only one nozzle hole is ejected to match the landing position with respect to the simultaneous ejection of all 300 nozzle holes with the slowest ink ejection speed. Is set to 900 ns. That is, all are delayed in accordance with the simultaneous ejection of the 300 nozzle holes with the slowest ink droplet ejection speed. Assuming that the landing position at the ink ejection speed when only one nozzle hole is ejected is assumed in an image that does not take into account the ideal delay, the forward path of the method of the second embodiment is 900 ns, and the return path is only 958 ns. There will be a delay with respect to the ideal. Therefore, in the forward path, the output timing of the LT signal is advanced by 900 ns, so that the output timing of the Vcom signal is also advanced by 900 ns, so that the target position can be landed. In the return path, the output timing of the LT signal is advanced by 958 ns, so that the output timing of the Vcom signal is also advanced by 958 ns, so that the target position can be landed and the deviation can be corrected.

  As described above, the deviation can be corrected by adjusting the output timing of the LT signal and the Vcom signal. Such a shift for each scan is automatically determined at least for each scan by the print start timing adjusting means formed in the recording head control unit 26 for the print start timings of the LT signal and the Vcom signal set by measurement in advance. By setting to, it becomes possible to adjust appropriately.

(Third embodiment)
Next, a third embodiment of the image forming apparatus according to the present invention will be described. As a result of various studies by the inventors, the occurrence of undershoot, overshoot, and rise / fall delay due to fluctuations in the drive voltage described above is also affected by changes in conditions such as temperature changes. It was found that the faster the change in waveform (the faster the rise and fall speeds), the larger (the worse the deterioration), and the smaller the change, the smaller.

  That is, as described above, the larger the number of dots to be written simultaneously, the more the voltage waveform for driving the piezoelectric element collapses. In addition, the rising and falling speeds of the driving waveform also cause a large increase in current. I found out. Therefore, when the drive waveform has the fastest rising / falling speed and the number of nozzles ejected simultaneously is large, the drive waveform is most deformed.

  Therefore, in the image forming apparatus according to the third embodiment, the recording head controller 26 further includes a correction table (second correction table) in which the correction amount of the output timing corresponding to the type of waveform of the drive waveform output signal is stored. The drive waveform controller 26c provides a drive waveform output signal based on the output timing corrected based on the correction table (first correction table) for the number of nozzles and the correction table (second correction table) for the type of drive waveform. It is fed to the recording head drive unit 30A and corrected according to the number of nozzles discharged simultaneously and the rising and falling speeds of the drive waveform.

  FIG. 19 is a functional block diagram of the recording head control unit 26 according to the present embodiment. The recording head control unit 26 includes a ROM 26f in addition to the recording head control unit (first embodiment) shown in FIG.

  An example of drive waveform information stored in the ROM 26f is shown in FIG. As shown in FIG. 20, the drive waveform information is obtained by associating and storing a waveform rank corresponding to each type of waveform (drive waveform data stored in the ROM 24). The waveform rank is obtained by classifying the driving waveform rising and falling speeds. In the example shown in FIG. 20, the lower the speed, the smaller the numerical value of the rank, and the higher the speed, the higher the numerical value of the rank. .

  The influence on the rise and fall speed waveforms of the drive waveform will be described. First, as the speed increases, the current that flows instantaneously increases. The increase in the instantaneous current increases the influence of the inductance component of the transmission path, so that the distortion of the waveform increases. This distortion of the waveform causes the ink ejection speed (Vj ). Therefore, it is necessary to increase the delay amount of the output timing when the discharge speed is fast and to reduce the delay amount of the output timing when the discharge speed is slow so that the influence does not appear in the image.

  However, the relationship between the waveform distortion and the discharge speed may be slower as the distortion is larger, or may be faster as the distortion is larger. In the present embodiment, an example will be described in which the rise and fall speeds are fast and the waveform distortion is large, the delay amount for correcting the discharge speed is small, and the delay amount for correcting is large as the rise and fall is slow. It is not limited to this.

  Next, FIG. 21 shows a correction processing flow of the drive waveform output signal in the third embodiment. First, when a print command is generated (step S21), image data and a drive waveform are set by software (step S22). At this time, the drive waveform data and rank (drive waveform information) are read from the ROM 26f to the drive waveform controller 26c. Note that the output timing correction value of the drive waveform is not fixed and is not set by software.

  Next, printing is started by software (step S23). Image data is output by hardware (step S24), and the number of nozzle holes for simultaneously discharging the output signal by the image data count circuit 26b is counted (step S25).

  The output correction value is determined by referring to the correction table (first and second correction table) 26d based on the count result and the rank of the selected drive waveform (step S26), and the drive waveform signal corrected by this output correction value. Is output to the head drive unit 30A (step S27), and the actuators 10Y1 to 10YN are operated to eject ink droplets from the corresponding nozzle holes 10 (step S28).

  Next, FIG. 22 shows an example of the timing correction table 26d in the present embodiment. 22A shows a first correction table (nozzle number) in which a correction amount based on the number of nozzles is recorded, and FIG. 22B shows a second correction table (drive waveform information) based on the drive waveform information.

  The correction table for the number of nozzles shown in FIG. 22A stores a delay time t1 (ns) corresponding to the number of nozzles, and the waveform corresponding to the type of drive waveform shown in FIG. 22B. In the rank correction table, a delay time t2 (ns) corresponding to the rank of the drive waveform is stored.

  Therefore, the correction value can be determined based on the delay times t1 and t2 obtained based on the number of nozzles and the waveform rank. The correction amount may be calculated by, for example, tD = t1 + t2. However, the correction amount calculation method is not particularly limited, and one correction amount may be emphasized by weighting processing or the like.

  As described above, since the voltage control is performed by correcting the driving voltage in consideration of the number of nozzles to be ejected simultaneously and the type of the driving waveform, the desired ink can be ejected and a desired image is output. be able to. More specifically, by correcting the output timing according to the number of nozzles to be ejected simultaneously and the rising and falling speeds of the drive waveform, even when the ink ejection speed (Vj) generated due to the difference in the number of nozzles varies, The landing position on the paper can be set as a desired place, and the image quality can be improved.

  Also in the third embodiment, it is preferable that a recording head control unit corresponding to each color is provided as in the first embodiment (see FIG. 10). As a result, correction can be performed for each recording head, and correction in consideration of variations unique to each head can be performed.

  In addition, even in an image forming apparatus having a configuration in which the color of ink ejected by each recording head is different, it is preferable to include a recording head control unit corresponding to each color as shown in FIG. This makes it possible to correct for each recording head. Since ink has different properties such as viscosity for each color, as shown in FIGS. 24A and 24B, a correction table is provided for each color for further correction in consideration of the difference in properties. Image quality can be improved.

  Also, as shown in FIGS. 25A and 25B, in the third embodiment as well, as in the first embodiment (see FIG. 15), the table for the forward path and the return path (the correction table for reciprocation) ) Is also preferable. A flowchart of the correction process in this case is shown in FIG. In the correction process shown in FIG. 26, when determining the output correction value, the table to be referred to is changed in the forward path or the return path (steps S36-1 to S36-3), and the correction value is determined in accordance with the recording direction ( Step S36-4). Accordingly, since correction can be made for each traveling direction of the recording head, it is possible to perform correction in consideration of characteristics such as airflow in the apparatus and inclination of the carriage depending on the traveling direction of the carriage. Steps S31 to 35 and S37 to 38 correspond to steps S21 to 25 and S27 to 28 in FIG.

  Further, as described above, when an image as shown in FIG. 17 is printed by bidirectional printing, there is a possibility that an image shift for each scan occurs as shown in FIG. Hereinafter, in addition to the correction method by the print start timing adjustment unit in the second embodiment, an example of correction when driving waveform information is considered will be described.

  Also in the third embodiment, as in the second embodiment, for example, the correction of the number of ejection nozzles is performed by adjusting only one nozzle in order to adjust the landing position with respect to the simultaneous ejection of 300 nozzles at which the ink ejection timing is the slowest. The delay when not discharging is set to 900 ns. That is, all are delayed in accordance with the simultaneous ejection of 300 nozzles with the slowest ink ejection speed. In the correction of the waveform rank, all are delayed in accordance with rank 1 where the ink ejection timing is the latest.

  In an ideal image in which no delay is considered, assuming a landing position when ink discharge is discharged under the condition of waveform rank 5 when only one nozzle is discharged, for example, 1300 ns (900 ns + 400 ns) in the forward path On the return path, 1402 ns (958 ns + 444 ns), a delay occurs with respect to the ideal. In this case, it is possible to land at a desired position by increasing the output timing of the LT signal by 1300 ns in the forward path, and it is possible to land at the desired position by increasing the output timing of the LT signal by 1402 ns in the return path. It is also possible to correct image misalignment for each scan.

  The above-described embodiment is a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Carriage 1a Connecting part 2 Guide rod 3 Main scanning motor 4 Timing belt 5 Encoder sheet 6 Main scanning encoder sensor 7 Sub scanning motor 8 Recovery device 9A, 9B, 91, 92, 93, 94 Recording head 10 Nozzle holes 10Y, 10C , 10M, 10K Nozzle hole arrays 10Y1 to 10YN Actuators 11, 12, 16, 17 Pulley 13 Rotating shaft 14 Support shaft 15 Conveying belt 18 Timing belt 19 Encoder disk 20 Subscanning encoder sensor 21 Host PC
22 Host I / P
23 CPU
24 ROM
25 RAM
26, 26Y, 26C, 26M, 26K, 26Y1, 26Y2, 26Y3, 26Y4 Recording head control unit 26a Image data control unit 26b Image data count circuit 26b1 Counter 26c Drive waveform control unit 26d Timing correction table 26e Drive waveform shaping unit 26f ROM
27 Main scanning control unit 28 Sub scanning control unit 29 Buses 30A, 30B, 30C, 30D Recording head drive unit 31 Shift register 32 Latch 33 Gradation decoder 34 Level shifter 35 Analog switch

Japanese Patent Laid-Open No. 11-58735 JP 2007-203491 A

Claims (6)

A recording head having a nozzle hole array in which a plurality of nozzle holes for discharging ink droplets by driving a piezoelectric element are arranged;
A recording head drive unit for driving the piezoelectric element of the recording head;
An image data signal and a drive waveform output signal for driving the piezoelectric element of the recording head according to the image data signal are sent to the recording head driving unit, and ink droplets from the nozzle holes of the recording head are sent. In an image forming apparatus including a recording head control unit that controls ejection,
The recording head controller is
Image data counting means for simultaneously counting the number of nozzle holes for ejecting ink droplets from the image data signal;
A first correction table storing a correction amount of an output timing of a drive waveform output signal for driving the piezoelectric element according to the number of nozzle holes counted by the image data counting means;
An image forming apparatus comprising: a drive waveform control unit that sends the drive waveform output signal to the recording head drive unit at an output timing based on the first correction table. The recording head controller is
A second correction table storing a correction amount of the output timing of the drive waveform output signal according to the type of waveform of the drive waveform output signal;
2. The image formation according to claim 1, wherein the drive waveform control unit sends the drive waveform output signal to the recording head drive unit at an output timing based on the first and second correction tables. apparatus. The image forming apparatus according to claim 1, wherein
2. The image forming apparatus according to claim 1, wherein the recording head includes a plurality of nozzle hole arrays, and ejection of ink droplets is controlled by the recording head control unit for each nozzle hole array. The image forming apparatus according to any one of claims 1 to 3,
The recording head has a nozzle hole row that discharges ink droplets of different colors, and the ejection of ink droplets is controlled by the recording head controller for each nozzle hole row that discharges ink droplets of different colors. An image forming apparatus. The image forming apparatus according to claim 1,
The recording head is mounted so as to be capable of reciprocating in the main scanning direction, and includes a reciprocal correction table for correcting the output timing of the drive waveform output signal in the forward path and the backward path, and the reciprocal correction. An image forming apparatus, wherein a discharge timing of ink droplets from the nozzle holes of the recording head can be changed between a forward pass and a return pass using a table. The image forming apparatus according to claim 1,
The recording head scans in the main scanning direction and adjusts the printing start timing of the drive waveform output signal every time scanning is performed when an image is formed by ejecting ink droplets from the nozzle holes. Printing start timing adjusting means for the recording head control unit,
An image forming apparatus characterized in that the discharge start timing of ink droplets from the nozzle holes of the recording head can be changed using the print start timing adjusting means each time scanning is performed.