JP2004001479A - Drive controlling method for ink jet head, and ink jet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive controlling method for an ink jet head capable of easily achieving gradation printing by an electrostatic ink jet head for one-pixel printing by ejecting ink droplets by a plurality of times. <P>SOLUTION: An ink jet head drive controlling unit 1 for an ink jet printer carries out one-pixel printing by ejecting ink droplets by a plurality of times so that the gradation is modulated by increasing or reducing the number of the ink ejecting operations in a one-pixel printing period. A nozzle driving waveform signal is produced so that the ink droplet ejecting operation is always executed continuously in the one-pixel printing period, and the final ink droplet ejection is executed certainly by the final ejection timing of the one-pixel printing period. Compared with the case of executing a plurality of ink ejecting operations discontinuously in the one-pixel printing period, the nozzle drive control can be facilitated, and the printing process speed can be made higher. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a drive control method of an inkjet head including an electrostatic actuator that vibrates a vibration plate formed in a part of an ink chamber communicated with an ink nozzle by an electrostatic force, particularly for performing gradation expression and the like, and In order to suppress the variation in the ejection mass of ink droplets due to the individual difference of the inkjet head, the driving of the inkjet head suitable for forming one print pixel by ejecting the ink droplets once or more times. The present invention relates to a control method and an ink jet printer.
[0002]
[Prior art]
Patent Documents 1, 2, and 3 disclose an ink jet head including an electrostatic actuator that discharges ink droplets by changing the volume of an ink chamber that stores ink using electrostatic force. Are known.
[0003]
In addition, an ink jet printer having such an electrostatic ink jet head is known which has a print mode in which one pixel for printing is formed by discharging ink droplets a plurality of times (multiple shots). I have. For example, Patent Literature 4 discloses a method of forming one print pixel by multiple shots. The invention is not limited to the electrostatic type, and is similarly disclosed in Patent Document 5.
[0004]
[Patent Document 1]
JP-A-6-71882
[Patent Document 2]
JP-A-6-55732
[Patent Document 3]
JP-A-5-50601
[Patent Document 4]
JP-A-2001-322265
[Patent Document 5]
JP-A-5-124218
[0005]
[Problems to be solved by the invention]
In such an ink jet printer, the size of each pixel can be changed by increasing or decreasing the number of shots forming one print pixel, and the gradation of each pixel can be expressed, which is convenient.
[0006]
Here, when performing color printing, it is necessary to increase the number of shots forming one print pixel in order to perform gradation expression in multiple stages. In addition, when the number of shots is increased, the ink mass per shot is inevitably reduced. In order to secure the same density as in the past when printing characters and the like, the number of shots per pixel of printing is required. Need to be increased. From this viewpoint, the necessity of multi-shot drive has been increasing, such as 6-shot / dot drive in which one print pixel is formed by 6 shots.
[0007]
When gradation expression in color printing is performed in multiple stages by performing such multi-shot driving, the following problem that has not been noticed in the past occurs.
[0008]
When performing gradation expression in color printing of a picture, a photograph, or the like in multiple stages, it is necessary to set the number of shots for each pixel according to the gradation and perform each shot continuously or in a discontinuous state. Need to be set. Therefore, if the multi-shot driving is not performed properly, there is a problem that control for generating a driving signal waveform for the multi-shot driving becomes complicated.
[0009]
For example, when printing one pixel with a maximum of six shots, if two shots are selected, two shot time points are selected from the six shot time points. In this case, there are 15 combinations when selecting two out of six. Therefore, unless the two shot times are set appropriately, the control becomes complicated.
[0010]
Next, in the case of performing multi-shot driving, it is possible to eliminate variations in print density caused by variations in ink ejection mass and the like due to individual differences between inkjet heads by adjusting the number of shots. That is, the number of shots that can secure a desired print density is obtained in advance for each ink jet head, and this is carried on each ink jet head as head rank information. Is printed, it is possible to suppress variations in print density.
[0011]
For example, in an inkjet printer that performs multi-shot driving capable of printing one pixel with a maximum of six shots, if the number of shots represented by the head rank is three, characters are printed in three shots. Also in this case, if each shot is not properly performed, there is a problem that printed characters are missing and the print quality is reduced.
[0012]
For example, in the case of printing the number "1", if the time to perform three shots from the time of six shots is selected discontinuously, the line of the character may be missing and the print quality may deteriorate. As an example, when three shots are continuously performed as shown in FIG. 17A, the landing of each shot in one pixel is connected, but two shots are continuously performed and the last shot is performed. Is performed at the end of six shots, as shown in FIG. 17 (b), the impact of the last one shot is separated, a shadow is formed in the character, and the print quality deteriorates. Is not preferred.
[0013]
SUMMARY OF THE INVENTION It is an object of the present invention to stabilize the print quality to be formed in an ink jet printer that performs printing for one pixel with multiple shots.
[0014]
Another object of the present invention is to make it possible to easily perform printing operation control with different numbers of shots in an ink jet printer that performs printing for one pixel with multiple shots.
[0015]
[Means for Solving the Problems]
In order to solve the above problems, the present invention applies a drive voltage pulse to an electrostatic actuator to eject ink droplets from an ink nozzle, and prints one pixel one or more times. In the drive control method of the inkjet head formed by
When performing printing for one pixel by ejecting ink droplets a smaller number of times than the number of ejections of ink droplets included in one pixel printing period, it is necessary to perform a continuous ink droplet ejection operation. Features.
[0016]
In the present invention, when printing for one pixel is formed by discharging ink droplets a plurality of times, a continuous ink droplet discharging operation is always performed. In comparison with the case where a plurality of ink ejections are performed in a discontinuous state during a one-pixel printing period and printing for one pixel is performed, the collection of the ejected ink droplets that land on the recording medium is better. In this case, it is possible to stabilize the quality of a printed image when one-pixel printing is performed by discharging the ink droplets of the above.
[0017]
In addition, in the conventional multi-shot one-pixel printing, it is necessary to set at which time among the ejection times in the one-pixel printing period ink droplets are ejected, except when printing is performed with the maximum number of ejections. However, in the present invention, since the ink droplets are always continuously ejected the required number of times, it is only necessary to determine the first ejection point or the last ejection point regardless of the number of ejections.
[0018]
Therefore, software processing for generating a drive voltage pulse corresponding to each number of ejections becomes extremely simple, and the calculation processing time is thereby shortened. Therefore, it is possible to lower the rank of the components such as the CPU for controlling the driving of the ink jet head, and to reduce the cost. Further, since the calculation processing time is shortened, the print waiting time from the print command to the start of printing can be reduced, and the processing speed can be increased.
[0019]
Here, the drive control method according to the present invention can be used when the number of ejections of ink droplets for printing one pixel is changed to control the gradation of the pixel.
[0020]
In addition, the drive control method according to the present invention provides a method for controlling the number of ejections of ink droplets for forming one pixel of printing for each inkjet head in order to suppress a variation in the ejection mass of ink droplets due to individual differences between inkjet heads. Can be applied to the case where is set in advance.
[0021]
In this case, a head rank relating to a preset number of ejections of ink droplets is detected, and the number of ejections of ink droplets for forming one print pixel is determined based on the detected head rank relating to the number of ejections. If the number of ejections is less than the maximum number of ejections, the necessary number of ink droplets may be continuously ejected within one pixel printing period to print each pixel.
[0022]
Next, in the drive control method of the present invention, when printing one pixel by continuous ejection of ink droplets, the ejection of the last ink droplet is performed at the last ejection point in the one-pixel printing period. Is desirable.
[0023]
With this configuration, after performing continuous ejection of ink droplets for printing one pixel, an auxiliary voltage pulse for preventing unnecessary ink droplets from being ejected from the ink nozzle is applied to the electrostatic actuator. When applying, the application time point of the auxiliary voltage pulse can always be the last time point of the printing period for one pixel. Therefore, the process for generating the drive voltage pulse including the auxiliary voltage pulse is extremely simple, which is preferable.
[0024]
Here, the operation and effect of the auxiliary voltage pulse are as follows. When forming one pixel of printing by discharging ink droplets a plurality of times, pressure fluctuations generated by electrostatic force due to a plurality of driving voltage pulses are superimposed on the ink flow path communicating with the ink nozzle. In some cases, a residual pressure fluctuation that causes unnecessary ink droplets to be ejected from an ink nozzle may occur. By using the auxiliary voltage pulse, such a residual pressure fluctuation can be suppressed or eliminated.
[0025]
Next, when using the auxiliary voltage pulse, it is preferable to detect the ambient temperature of the inkjet head and apply the auxiliary voltage pulse only when the ambient temperature is equal to or higher than a predetermined value. When the auxiliary voltage pulse is applied, the printing speed of one pixel is reduced because the printing period of one pixel is extended by an amount corresponding to the addition of the auxiliary voltage pulse. Therefore, it is preferable that the auxiliary voltage pulse is not used except at the time of use at a high temperature where unnecessary ink droplets are likely to be generated after continuous ejection, so that an unnecessary decrease in printing speed can be avoided.
[0026]
Next, in an ink jet head that ejects ink droplets by an electrostatic actuator, when a drive voltage pulse of the same polarity is repeatedly applied to the electrostatic actuator, the counter electrode is charged and the proper ink ejection operation cannot be continued. There is a risk. Therefore, when printing for one pixel is performed by discharging ink droplets a plurality of times, it is desirable to apply the drive voltage pulse whose polarity is alternately inverted to the electrostatic actuator.
[0027]
Next, the present invention relates to an ink jet printer,
An ink nozzle for ejecting ink droplets,
An ink chamber communicating with the ink nozzle and holding ink;
An electrostatic actuator including a vibration plate elastically displaceable in an out-of-plane direction forming a part of the ink chamber and a counter electrode arranged to face the vibration plate at a predetermined interval,
An inkjet head drive control device for applying a drive voltage pulse to the electrostatic actuator to eject ink droplets from the ink nozzles and forming a print for one pixel by ejecting ink droplets one or more times; Has,
The ink jet head drive control device is configured to print a continuous ink liquid when one pixel is printed by ejecting ink droplets a smaller number of times than the number of ink droplet ejections included in one pixel printing period. A driving voltage pulse generating means for generating the driving voltage pulse for performing a droplet discharging operation is provided.
[0028]
Here, the inkjet head drive control device can be configured to control the gradation of the pixel by changing the number of ejections of ink droplets for printing one pixel.
[0029]
Further, the inkjet head drive control device includes:
A discharge rank head rank setting unit in which a head rank relating to the discharge count for forming one pixel of printing is set;
The number of ejections calculating means for calculating the number of ejections of ink droplets for forming one printing pixel based on the head rank relating to the number of ejections set in the number-of-ejections head rank setting means. Can be.
[0030]
In this case, the driving voltage pulse generating means is configured to generate the driving voltage pulse for forming one pixel of printing at the calculated number of ejections.
[0031]
Further, when printing one pixel by continuous ejection of ink droplets, the drive voltage pulse generating means sets the ejection of the last ink droplet as the ejection point of the last ink droplet in one pixel printing period. Preferably, the driving voltage pulse is generated.
[0032]
In this case, the driving voltage pulse generating means performs an auxiliary voltage pulse for preventing unnecessary ink droplets from being ejected from the ink nozzles after performing continuous ejection of ink droplets for printing one pixel. Is desirable.
[0033]
Here, it is preferable that the apparatus further includes a temperature detecting unit for detecting a surrounding environment temperature of the inkjet head, and the driving voltage pulse generating unit generates the auxiliary voltage pulse only when the surrounding environment temperature is equal to or higher than a predetermined value. .
[0034]
Next, when the printing of one pixel is performed by discharging ink droplets a plurality of times, it is preferable that the driving voltage pulse generating means generates the driving voltage pulse whose polarity is alternately inverted.
[0035]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of an inkjet printer including an electrostatic actuator to which the present invention is applied will be described with reference to the drawings.
[0036]
(overall structure)
FIG. 1 is a schematic block diagram showing an ink jet printer having the electrostatic actuator of the present embodiment, and FIG. 2 is a schematic configuration diagram of the electrostatic ink jet head.
[0037]
First, the configuration of the electrostatic inkjet head of the present embodiment will be described with reference to FIG. The electrostatic inkjet head 100 is configured by stacking a semiconductor substrate 102, a semiconductor substrate 103, and a glass substrate 104, and a plurality of ink nozzles 105 are formed on the semiconductor substrate 103. Independent ink chambers 106 communicating with the respective ink nozzles 105 are formed between the semiconductor substrates 102 and 103, and a vibration plate 107 capable of vibrating in an out-of-plane direction is formed on the bottom wall of each ink chamber 106. Is formed.
[0038]
Each vibrating plate 107 functions as a common electrode, and a concave portion is formed on the surface of the glass substrate 104 facing the respective vibrating plates 107. On the bottom surface, individual concave portions facing the vibrating plates 107 at predetermined intervals are provided. An electrode 109 is formed. Each of the vibration plates 107 and the individual electrodes 109 facing each other constitute an electrostatic actuator. A driving voltage pulse is applied to this electrostatic actuator, that is, the vibration plate 107 is vibrated by utilizing an electrostatic force generated by applying a driving voltage pulse between each vibration plate 107 and the individual electrode 109. ing. Due to the vibration of the vibration plate 107, the volume of the ink chamber 106 increases and decreases, whereby the ink droplet 110 is ejected from the ink nozzle 105 communicating with the ink chamber 106 based on the fluctuation of the ink pressure generated in the ink chamber 106. Is done.
[0039]
The electrostatic inkjet head 100 of the present example includes, for example, 64 ink nozzles 105 formed in a line on the semiconductor substrate 103, and selectively ejects ink droplets from these 64 ink nozzles 105. This makes it possible to print desired characters and images.
[0040]
Although the illustrated electrostatic inkjet head 100 is of a face eject type in which ink droplets are ejected from ink nozzles provided on the upper surface of the semiconductor substrate 103, the electrostatic inkjet head to be controlled by the present invention includes: An edge eject type in which ink droplets are ejected from an ink nozzle provided at an end of the substrate may be used.
[0041]
Next, referring to FIG. 1, the ink jet printer of the present embodiment has an ink jet head drive control device 1 for driving and controlling the electrostatic ink jet head 100. Has an inkjet head control unit 2 mainly composed of a CPU. Printing information is supplied to the CPU from the external device 3 via a bus, and a ROM, a RAM, and a character generator 4 are connected via an internal bus.
[0042]
The inkjet head control unit 2 executes a control program stored in the ROM, using a storage area in the RAM as a work area, and executes a control signal for driving the inkjet head based on character information generated from the character generator 4. Generate The control signal becomes a drive control signal corresponding to the print information via the logic gate array 5 and the drive pulse generation circuit 6, and is supplied to the head driver IC 9 formed on the head substrate 8 via the connector 7. . The head driver IC 9 is also supplied with a driving voltage pulse signal V3, a control signal LP, and a polarity inversion control signal REV.
[0043]
In the head driver IC 9, a driving voltage pulse to be applied to each of the vibration plates 107 of the electrostatic inkjet head 100, that is, a common electrode is determined based on the above-described signals supplied and the driving voltage Vp supplied from the power supply circuit 10. A drive voltage pulse to be output from the common output terminal COM and to be applied to each counter electrode (individual electrode) 109 corresponding to each ink nozzle 105 is output from the number of individual output terminals SEG corresponding to each individual electrode. The potential difference between the output of the common output terminal COM and the output of the individual output terminal SEG is applied between each of the vibration plates 107 corresponding to each of the ink nozzles 105 and the individual electrode 109 facing each. A driving potential difference waveform in a designated direction is applied during driving (when ink droplets are ejected), and no driving potential difference is applied when not driving.
[0044]
Here, on the head substrate 8, a shot rank identification circuit 12 carrying information on the number of ejections (the number of shots) for forming one print pixel, and information on the pulse width of the drive voltage pulse. (Pulse width head rank) is carried by a pulse width rank identification circuit 13. The ejection rank head rank carried by the shot rank identification circuit 12 is detected by the shot rank detection circuit 14 of the ink jet head control unit 2, and one pixel of printing is determined under the control of the CPU based on the detected ejection count head rank. The number of ejections of ink droplets for forming is calculated. The pulse width head rank carried by the pulse width rank identification circuit 13 is detected by the pulse width rank detection circuit 15 of the ink jet head control unit 2, and the pulse width of the drive voltage pulse is determined based on the detected pulse width head rank. Is calculated.
[0045]
A thermistor 16 for detecting the ambient temperature of the electrostatic ink jet head 100 is mounted on the head substrate 8, and a detection signal from the thermistor 16 is transmitted to the temperature detection circuit 17 of the ink jet head control unit 2 by A / A. It is D-converted so that the ambient temperature is detected.
[0046]
The drive pulse generating circuit 6 generates a control signal LP for forming one pixel of printing with the drive voltage pulse having the finally determined pulse width and the number of ejections, and outputs the control signal LP to the head driver IC 9.
[0047]
FIG. 3 is a schematic block diagram illustrating an example of the internal configuration of the head driver IC 9. The head driver IC 9 is a CMOS 64-bit output high withstand voltage driver that operates by being supplied with a high-voltage drive voltage Vp and a logic circuit drive voltage Vcc from the power supply circuit 10. The head driver IC 9 switches between the driving voltage pulse and the GND potential according to the supplied driving control signal and applies the switching between the opposing electrodes corresponding to the respective ink nozzles of the inkjet head 100.
[0048]
The number 91 in the head driver IC 9 indicates a 4-bit shift register. The shift register 91 shifts up a 64-bit DI signal input transmitted from the logic gate array 5 as serial data by an XSCL pulse signal input which is a basic clock pulse synchronized with the DI signal, and shifts the data. This is a static shift register stored in a register in the memory 91. The DI signal is a control signal indicating ON / OFF of selection information for selecting each of the 64 ink nozzles, and this signal is transmitted as serial data.
[0049]
Reference numeral 92 denotes a 64-bit latch circuit which latches 64-bit data stored in the shift register 91 by a latch pulse LP to store the data, and outputs the stored data to a 64-bit inversion circuit 93 as a signal. It is a tea clutch. In the latch circuit 92, the DI signal of the serial data is converted into a 64-bit parallel signal for outputting a 64-segment for driving each ink nozzle.
[0050]
The inverting circuit 93 outputs an exclusive OR of the signal input from the latch circuit 92 and the REV signal to the level shifter 94. The level shifter 94 is a level interface circuit that converts the voltage level of the signal from the inverting circuit 93 from a logic system voltage level (5 V level or 3.3 V level) to a head drive system voltage level (0 V to 45 V level).
[0051]
The SEG driver 95 has a transmission gate output of 64 channels, and outputs either a drive voltage pulse input or a GND input to the segment outputs of SEG1 to SEG64 by the input of the level shifter 94. The COM driver outputs either a drive voltage pulse input or a GND input to the REV input to the COM.
[0052]
Each signal of XSCL, DI, LP and REV is a signal of a logic system voltage level, and is a signal transmitted from the logic gate array 5 to the head driver IC 9.
[0053]
By configuring the head driver IC 9 in this manner, even when the number of segments to be driven (the number of nozzles) increases, the drive voltage pulse for driving each ink nozzle of the head and GND can be easily switched, and the above-described correctness can be obtained. Reverse alternating drive can be easily realized.
[0054]
(Print mode)
Here, in the inkjet head drive control device 1 of the present embodiment, it is possible to perform print control in a plurality of print modes. In the case of this example, two shot (shot) / dot (dot) driving, in which one printing pixel is formed by discharging two consecutive ink droplets at a maximum, and three consecutive ink droplet discharges are performed. Printing is performed by 3 shot / dot drive to be formed, 4 shot / dot drive to be formed by consecutively discharging ink droplets up to 4 times, and 6 shot / dot drive to be formed by continuous ink droplet discharge up to 6 times. Is possible.
[0055]
Further, in each driving state, it is possible to control the gradation of each pixel by changing the number of ejections of ink droplets in one pixel printing period.
[0056]
The print mode in each of the above-described drive modes can be selectively switched by an input from the external device 3 side.
[0057]
FIGS. 4 to 7 show signal waveforms of respective sections in a print mode by 2 shot / dot drive, 3 shot / dot drive, 4 shot / dot drive, and 6 shot / dot drive. In each figure, a drive voltage pulse signal V3, a control signal (latch pulse) LP, a polarity inversion control signal REV, a COM output which is an output of the common terminal COM, and an individual terminal are supplied from the inkjet head control unit 2 to the head driver IC 9. The SEG output, which is the output of the SEG, and the COM-SEG potential difference, which is the potential difference (nozzle drive voltage waveform) generated between the common electrode (diaphragm 107) and the individual electrode 109, are shown.
[0058]
The print mode by 2 shot / dot drive shown in FIG. 4 is one in which one pixel (dot) is formed by continuous ejection of ink droplets (shots) at a maximum of two times, and one dot is formed by two shots by the control signal LP. Is controlled to form
[0059]
Further, in this printing mode, as shown in a waveform diagram showing the COM-SEG potential difference, by increasing or decreasing the number of shots in one pixel printing period T, it is possible to perform pixel printing with three gradations. That is, the one-pixel printing period T1 is a two-shot driving period, and pixel printing with the highest density can be realized. The subsequent one-pixel printing period T2 is a non-driving period and no shot is performed, so that a pixel portion with the lowest density is formed. The subsequent one-pixel printing period T3 is a driving period of only one shot, and Density pixel printing can be realized.
[0060]
Here, in the one-pixel printing period T3 in which only one shot is performed, a drive voltage pulse is applied at the latter half of the two shots included in this period T3 to eject ink droplets. I have to.
[0061]
In addition, when printing one pixel by a continuous ejection operation, the polarity is controlled by the inversion control signal REV so that the polarity of the nozzle drive waveform applied between the opposed electrodes is inverted.
[0062]
Similarly, the print mode by the 3-shot / dot drive shown in FIG. 5 is to form one print pixel by continuously discharging ink droplets up to three times. In this printing mode, four gradation printing can be performed by performing shot modulation of four gradations. That is, the first gradation having the highest density is obtained by performing three consecutive shots in the one-pixel printing period T, the second gradation is obtained by performing two shots, and the third gradation is obtained. The gray scale is obtained by performing one shot, and the fourth gray scale is obtained by setting the non-drive state.
[0063]
Also in this case, when performing two shots for realizing the second gradation, the shot is performed at two consecutive shot timings in the latter half of three shot timings within one pixel printing period T. Like that. Further, one shot for realizing the third gradation is performed at the last shot timing in the one-pixel printing period T. Further, the nozzle drive waveform applied between the opposing electrodes is controlled by the inversion control signal REV so as to alternately change in reverse, positive, and reverse polarities.
[0064]
The print mode by the 4-shot / dot drive shown in FIG. 6 is one in which one pixel of print is formed by continuously discharging ink droplets up to four times. In this print mode, five gradation printing can be performed by performing five gradation shot modulation. In other words, the first gradation having the highest density is obtained by performing four consecutive shots in the one-pixel printing period T, the second gradation is obtained by performing three shots, and the third gradation is obtained. The gray scale is obtained by performing two shots, the fourth gray scale is obtained by performing one shot, and the fifth gray scale is obtained by not driving.
[0065]
Also in this case, when performing three shots for realizing the second gradation, the shot is performed at three consecutive shot timings in the latter half of the four shot timings within one pixel printing period T. Like that. In addition, two shots for realizing the third gradation are shot at the last two consecutive shot timings of the four shot timings in one pixel printing period T. Further, one shot for realizing the fourth gradation is performed at the last shot timing in the one-pixel printing period T.
[0066]
Further, the nozzle drive waveform applied between the opposed electrodes is controlled by the inversion control signal REV so as to alternately change in the positive, reverse, positive, and reverse polarities.
[0067]
In the print mode by 6 shot / dot drive shown in FIG. 7, one print pixel is formed by discharging ink droplets up to six times in succession. In this print mode, seven gradation printing can be performed by performing shot modulation of seven gradations. In other words, the first grayscale having the highest density is obtained by performing six consecutive shots in the one-pixel printing period T, the second grayscale is obtained by performing five shots, and the third grayscale is obtained. The gray scale is obtained by performing four shots, the fourth gray scale is obtained by performing three shots, the fifth gray scale is obtained by performing two shots, and the sixth gray scale is obtained. Can be obtained by performing one shot, and the seventh gradation can be obtained by setting the non-drive state.
[0068]
Also in this case, when performing five shots for realizing the second gradation, the shot is performed at the second consecutive five shot timings of the six shot timings in one pixel printing period T. Like that. In addition, four shots for realizing the third gradation are shot at four consecutive shot timings in the latter half of six shot timings in one pixel printing period T. Further, three shots for realizing the fourth gradation are performed in the latter three shot timings in the one-pixel printing period T. Similarly, two shots for the fifth gradation are performed at the second half shot timing. One shot for the sixth gradation is performed at the last shot timing.
[0069]
Also in this case, the nozzle drive waveform applied between the opposed electrodes is controlled by the inversion control signal REV so as to alternately change in positive, reverse, positive, reverse, positive, and reverse polarities.
[0070]
As described above, in the ink jet printer of the present embodiment, in the so-called multi-shot / dot print mode, printing of one pixel is formed by discharging ink droplets a plurality of times, continuous discharge of ink droplets is always performed. The operation is performed. As a result, compared to the case where a plurality of times of ink ejection is performed in a discontinuous state within one pixel printing period and printing of one pixel is performed, the collection of the ejected ink droplets that land on the recording medium is improved, The print quality of a print image formed by multiple shots / dots can be stabilized.
[0071]
Further, in this example, the drive voltage pulse is always applied to the electrostatic actuator by the required number of times continuously to eject the ink droplets by the required number of times continuously, and the last pulse of the continuous drive voltage pulse is applied. The nozzle drive waveform is formed such that the pulse at the final point in the one-pixel printing period is obtained regardless of the number of pulses (the number of shots). Therefore, when gradation expression is performed, a nozzle drive waveform having a configuration in which a required number of drive voltage pulses are arranged from the last pulse timing in each one-pixel printing period may be formed regardless of the number of shots.
[0072]
As a result, compared to a case where a plurality of shots are performed within a one-pixel printing period in a discontinuous state, a software for generating an ink nozzle driving waveform signal for one pixel printing corresponding to each gradation (each shot number) is provided. Wear processing becomes extremely simple. This also shortens the calculation processing time. Therefore, it is possible to lower the rank of the components such as the CPU for controlling the driving of the ink jet head, and to reduce the cost. Further, since the calculation processing time is shortened, the print waiting time from the print command to the start of printing can be reduced, and the processing speed can be increased.
[0073]
Further, in this example, the polarity of the potential difference applied for discharging the ink droplets is alternately inverted by the polarity inversion control signal REV. By inverting the polarity of the potential difference generated between the common electrode and the individual electrode in this way, a residual charge is generated between the electrodes, the electrostatic force fluctuates, and the desired ink ejection characteristics cannot be obtained. This can avoid the adverse effect of the situation.
[0074]
(Print mode with auxiliary voltage pulse)
Next, in the inkjet head drive control device 1 of the inkjet printer of the present embodiment, the ambient temperature of the inkjet head 100 is detected by the temperature detection circuit 17 using the thermistor 16. When the ambient temperature is high, unnecessary ink droplets may be ejected when multi-shot / dot printing is performed due to factors such as a decrease in ink viscosity.
[0075]
More specifically, in the case of forming one pixel of printing by continuously discharging ink droplets a plurality of times with the same ink nozzle, it is necessary to discharge the first and subsequent multiple times of ink droplets. Amplification of the pressure vibration due to mutual interference between the residual vibration of the first pressure change caused by the change in the volume of the ink chamber and the residual vibration of each pressure vibration generated from the second time until the last ink droplet ejection. In addition, there is a possibility that excessive ink droplets are ejected after the last ink droplet ejection.
[0076]
That is, when one pixel is formed by discharging a plurality of ink droplets and a pixel of a desired size or density is to be printed, surplus ink droplets are discharged after the last discharge of ink droplets. The ejection of the excess ink droplets causes ink mist to adhere to the printing surface or nozzle surface, causing problems such as deterioration of the printed image due to the ink mist or non-ejection of ink due to formation of an ink pool on the nozzle surface, and the printing result. The quality of the paper cannot be kept constant, or printing becomes impossible.
[0077]
Factors that cause excess ink droplets include a mismatch between a natural frequency of a vibration system including a vibration plate of an ink jet head and an ink flow path, and a drive frequency that repeatedly vibrates to form one pixel. . Furthermore, the dimensions of the diaphragm and ink nozzle that govern the natural frequency of the ink flow path, and the physical properties such as ink surface tension and viscosity that determine the ejection limit pressure of the ink droplets, may cause excessive ink droplet generation. It is mentioned as a factor.
[0078]
Therefore, in the ejection of the ink droplets a plurality of times, the driving frequency of the repetitive driving for forming one pixel is controlled so that the ink pressure in the ink chamber does not interfere with the residual vibration caused by each ejection. There is a need to.
[0079]
However, in order to discharge ink droplets normally and stably by this method, it is necessary to further control in consideration of the dimensional data of the vibration plate and the ink nozzle and the physical properties of the ink, which is difficult to realize. It is.
[0080]
Therefore, in a print mode in which one pixel is formed by successively discharging ink droplets a plurality of times, an auxiliary voltage pulse is applied after a plurality of drive voltage pulses for ink discharge which are continuously applied. It is desirable to adopt a method of suppressing or eliminating the residual pressure as described above to prevent unnecessary ejection of ink droplets.
[0081]
In particular, when the ambient environment temperature of the inkjet head 100 is high, there is a high possibility that such unnecessary ink droplets are ejected, and when the ambient environment temperature is low, such adverse effects are substantially ignored. can do.
[0082]
Therefore, in the inkjet head drive control device 1 of the present embodiment, when the detected ambient environment temperature is equal to or higher than the predetermined temperature, the drive voltage pulse in the print mode by the multi-shot / dot drive shown in FIGS. An auxiliary voltage pulse V3h is added to the signal V3 at the end of each one-pixel printing period to suppress or eliminate the residual pressure as described above, thereby preventing unnecessary ejection of ink droplets. .
[0083]
FIG. 8 shows a basic voltage waveform of the drive voltage pulse V3 and a voltage waveform of the auxiliary voltage pulse V3h used to realize such a print control method. 9 to 12 show timing charts of the printing operation in each printing mode to which the auxiliary voltage pulse V3h is added. 9 to 12 show print modes corresponding to FIGS. 4 to 7, respectively.
[0084]
In FIG. 8, a drive voltage pulse V3 discharges one shot of an ink droplet from an ink nozzle by one pulse application. Pwn (n = 1, 2,... K) is the pulse width of the drive voltage pulse V3 (n) for performing the n-th ejection, and Pwin (n = 1, 2,. This is a time interval between drive voltage pulses V3 (n) and V3 (n + 1) for performing the first and (n + 1) th ejections. As can be seen from the figure, the waveform of the auxiliary drive voltage pulse is slightly smaller than the basic voltage waveform.
[0085]
As can be seen from the timing charts of FIGS. 9 to 12, in each print mode, the timing of the last shot of the multiple shots is set to be the last shot timing in the one-pixel printing period. Therefore, unnecessary driving of the ink droplets can be prevented by performing driving by the auxiliary driving voltage pulse at the end of the one pixel printing period of the nozzle driving waveform signal in each printing mode. For this purpose, an auxiliary voltage drive pulse may be added at the end of each one-pixel printing period in the drive voltage pulse signal V3.
[0086]
As described above, in the inkjet head drive control device 1 according to the present embodiment, when one pixel is formed by discharging ink droplets a plurality of times in succession, the residual vibration of the first pressure change and the second and subsequent times occur. Since the amplification of the pressure oscillation due to the mutual interference of the residual oscillations of the respective pressure oscillations is regulated by the application of the auxiliary voltage pulse, the ejection of the surplus ink droplets can be prevented and the ink droplets can be stably ejected.
[0087]
Further, in order to prevent the ejection of the excess ink droplets, it is only necessary to add the auxiliary voltage pulse after the driving voltage pulse train for one pixel printing in which the ink droplets are ejected a plurality of times. Can be controlled by the common auxiliary voltage pulse V3h even when the control is performed, it is possible to generate the drive voltage pulse signal including the auxiliary drive voltage pulse by the same circuit as the circuit that generates the drive voltage pulse. The head driver IC 9 can be simplified, and a drive control device for an inkjet head that does not discharge excess ink droplets can be simply and easily realized. The simplification of the head driver IC 9 allows the driver IC 9 to be reduced in size and cost. When the number of nozzles of the head is large, the effect is increased.
[0088]
Furthermore, in this example, when using the auxiliary voltage pulse, the ambient temperature of the inkjet head is detected, and the auxiliary voltage pulse is applied only when the ambient temperature is equal to or higher than a predetermined value. When the auxiliary voltage pulse is applied, the printing speed of one pixel is reduced because the printing period of one pixel is extended by an amount corresponding to the addition of the auxiliary voltage pulse. Therefore, if the auxiliary voltage pulse is not used except at the time of use at a high temperature where unnecessary ink droplets are likely to be generated after continuous ejection, there is an advantage that unnecessary reduction in printing speed can be avoided.
[0089]
The number of auxiliary voltage pulses to be added is not limited to one, but may be plural. If the reduction in printing speed is not a problem, multi-shot / dot printing may be performed using a driving voltage pulse signal to which an auxiliary voltage pulse has been added, regardless of the ambient temperature.
[0090]
(Initial setting of pulse width of drive voltage pulse based on head rank)
Next, in the inkjet head drive control device 1 of the present embodiment, the pulse width of the drive voltage pulse is initially set as follows. A pulse width rank identification circuit 13 is mounted on the surface of the head substrate 8, and an optimum drive based on actual ink droplet ejection characteristics of the inkjet head 100 measured at the time of shipment of the inkjet head 100 is provided here. Pulse width head rank information indicating a pulse width initial value Pws of the voltage pulse is carried. The pulse width rank identification circuit 13 of this example includes short lands Rank 1, 2, and 3 of 3 bits. One terminal of each of the short lands Rank 1, 2, and 3 is grounded, and the other terminal is connected to the inkjet head via the connector 7. It is connected to the pulse width rank detection circuit 15 of the control unit 2.
[0091]
FIG. 13A shows a correspondence table of combinations of short-circuit states of the 3-bit short lands Ranks 1, 2, and 3, and pulse width head ranks A to H. FIG. 13B is a diagram showing an example of a correspondence relationship between each of the head ranks A to H and the optimum pulse width initial value Pws. The correspondence table 21 shown in this figure is stored in the ROM of the inkjet head control unit 2 in advance. FIG. 13C shows a graph of ink discharge characteristics (ink discharge weight or ink discharge speed) with respect to the pulse width Pw of the drive voltage pulse in the case of head ranks A, B, and G.
[0092]
As can be seen from these figures, the ink ejection characteristics were measured at the time of shipment of the inkjet head 100, and as a result, when it was found that the rank of the inkjet head 100 was A, in order to obtain certain characteristics, the drive It is necessary to set the pulse width initial value Pws of the voltage pulse to 18 μsec. To this end, as shown in the table of FIG. 13A, all the short lands Rank1, Rank2, and Rank3 of the pulse width rank identification circuit 13 may be short-circuited with solder. The head rank A set in this manner is detected on the side of the pulse width rank detection circuit 15, and when the CPU receives the detection result via the input / output port I / O, the head rank stored in the ROM in advance. The pulse width initial value Pws (= 18 μs) of the rank A is called and expanded in the RAM. As a result, the pulse width of the drive voltage pulse of the inkjet head 100 is basically set to the initial pulse width Pws.
[0093]
As described above, the inkjet head drive control device 1 of the present embodiment obtains the pulse width initial value Pws that optimizes the ink droplet ejection characteristics of the individual inkjet heads 100, and generates a drive voltage pulse using this. Therefore, the ink droplet ejection characteristics of the inkjet head 100 can be made uniform.
[0094]
(Initial setting of the number of shots for forming one pixel of print based on head rank)
The ink jet head drive control device 1 of the present example further sets an initial setting of the number of ejections of ink droplets (the number of shots) for forming one print pixel based on the shot rank carried by the shot rank identification circuit 12. Is going.
[0095]
That is, there is an individual difference in the ink droplet mass per shot of the inkjet head 100, and this cannot be solved only by setting the optimum pulse width initial value Pws. In particular, in the case where one print pixel is formed by discharging ink droplets a plurality of times, the variation in the ink droplet mass for each shot is superimposed, so that the print density greatly varies for each pixel.
[0096]
Therefore, in this example, when the inkjet head 100 is shipped, after the optimum pulse width initial value Pws is obtained as described above, the ejection of the ink droplets from the ink nozzles is performed using the driving voltage pulse having the pulse width. The mass is measured, and the ink jet heads are classified based on the measurement result, and this is carried by the shot rank identification circuit 12 as ejection number head rank information.
[0097]
FIG. 14 is a diagram illustrating an example of an inkjet head classified by rank based on actual measurement. As shown in this figure, the ink ejection mass per shot was measured at the time of shipment of the ink jet head, and divided into four ranges according to the variation amount. , B, C, D.
[0098]
Here, the example of FIG. 14 is based on the 6 shot / dot print mode. In this case, in the drive control device 1 of this example, the number of shots is assigned to the number-of-discharges head rank C so that one print pixel is formed by six shots, and the other number-of-discharges head ranks A, B, and D are The number of shots is 10, 8, and 4, respectively.
[0099]
FIG. 15 is a graph in which the effect of correcting the number of ink ejection shots of the inkjet head per pixel is compared with the number of shots before correction. In this graph, the line segments A to D represent variations in the ink droplet ejection amount when one pixel of printing is formed with the corrected number of shots by the inkjet heads belonging to the ranks A to D, respectively. On the other hand, the line segment E indicates a variation when one print pixel is formed by six shots without performing rank classification.
[0100]
As described above, when the ranking is not performed, the variation in the ink ejection mass is Δ1 but the variation is reduced to Δ2 by changing the number of shots according to the ranking. Therefore, even if the ink ejection mass per shot varies due to the individual difference of the inkjet head 100, the mass of the ink droplet per pixel is corrected by correcting the number of shots per pixel for each rank. Can be suppressed.
[0101]
Here, FIG. 16 shows a correspondence table between the ejection rank head ranks A to D and the corresponding shot number S in 6 shots / dot moat. Such a correspondence table 22 is stored in the ROM of the inkjet head control unit 2. Generally, a correspondence table between the number of ejections head rank and the number of shots in the n-shot / dot print mode (n = 1, 2, 3,...) Is stored.
[0102]
As shown in FIG. 1, the shot rank identification circuit 12 carrying the information on the number of ejections head ranks A to D also has a 4-bit short land RankA as shown in FIG. , RankB, RankC, and RankD. One terminal of each of the short lands RankA, RankB, RankC, and RankD is grounded, and the other terminal is connected to the shot rank detection circuit 14 of the inkjet head control unit 2 via the connector 7. ing.
[0103]
The state of the shot rank identification circuit 12 shown in FIG. 1 carries information that the short land RankB is in a short-circuit state, and therefore, the head rank of the number of ejections is B. The head rank B set in this way is detected by the shot rank detection circuit 14, and when the CPU receives the detection result via the input / output port I / O, the shot number correction value stored in the ROM in advance , The number of shots corresponding to rank B is retrieved and output.
[0104]
Therefore, in this example, the number of shots for one-pixel printing in the n-shot / dot printing mode is initially set by the initial setting based on the head rank. For example, when the head rank is B in FIG. 16, the number of shots for one-pixel printing in the above-described 6-shot / dot printing (see FIGS. 7 and 12) is set to “8” instead of “6”. Is done. Thereby, it is possible to prevent the print quality from being varied due to the individual difference of the inkjet head.
[0105]
(Other embodiments)
In the above example, since the print mode in which the auxiliary voltage pulse is applied is provided, at the time of discharging the last ink droplet in one pixel printing period, the last of the continuous ink droplet discharging in one pixel printing period is performed. Discharge is performed. Instead, the first ink droplet may be always ejected at the time of the first ink ejection within the one-pixel printing period. Alternatively, it is also possible to start the continuous ejection of ink droplets from a time point other than the first and last discharge times in the one-pixel printing period.
[0106]
【The invention's effect】
As described above, in the ink jet head drive control method and the ink jet printer provided with the electrostatic actuator of the present invention, the ink liquid is ejected a smaller number of times than the number of ink droplet ejections included in one pixel printing period. When printing for one pixel is performed by discharging droplets, a continuous ink droplet discharging operation is performed. Therefore, as compared with the case where a plurality of ink ejections are performed in a discontinuous state within one pixel printing period and printing for one pixel is performed, each ejection ink droplet that lands on the recording medium is better grouped. The print quality of a print image formed by multi-shot one-pixel printing can be stabilized.
[0107]
Further, since the ink droplets are always continuously ejected for the required number of times, it is only necessary to determine the first ejection point or the last ejection point within one pixel printing period regardless of the number of ejections. Good. Therefore, software processing for generating a drive voltage pulse corresponding to each number of ejections becomes extremely simple, and the calculation processing time is thereby shortened. Therefore, it is possible to lower the rank of the components such as the CPU for controlling the driving of the ink jet head and to reduce the cost. Further, since the calculation processing time is shortened, the print waiting time from the print command to the start of printing can be reduced, and the processing speed can be increased.
[0108]
Therefore, by using the drive control method of the present invention, it is possible to easily realize the control of changing the gradation of the pixel by changing the number of ejections of the ink droplets for printing of one pixel and achieving high quality. A gradation expression can be realized.
[0109]
Further, in the present invention, in order to suppress variations in the ejection mass of ink droplets due to individual differences between inkjet heads, the number of ejections of ink droplets for forming one print pixel is set in advance for each inkjet head. The number of ejections of ink droplets for one-pixel printing is set based on this. Also in this case, an effect is obtained that control for achieving one-pixel printing based on the set number of ejections can be easily realized. Further, the head driver IC 9 can be simplified, and the size and cost of the driver IC 9 can be reduced. When the number of nozzles of the head is large, the effect is increased.
[0110]
Next, in the present invention, continuous ejection is performed such that the last ink droplet is ejected at the last ejection point in the one-pixel printing period. With this configuration, after performing continuous ejection of ink droplets for printing one pixel, an auxiliary voltage pulse for preventing unnecessary ink droplets from being ejected from the ink nozzle is applied to the electrostatic actuator. In this case, the auxiliary voltage pulse may be added for one pixel at the end of the printing period. Therefore, processing for generating a drive voltage pulse including such an auxiliary voltage pulse becomes extremely simple.
[0111]
Further, in the present invention, when using the auxiliary voltage pulse, the ambient temperature of the inkjet head is detected, and the auxiliary voltage pulse is applied only when the ambient temperature is equal to or higher than a predetermined value. When the auxiliary voltage pulse is applied, the printing speed of one pixel is reduced because the printing period of one pixel is extended by an amount corresponding to the addition of the auxiliary voltage pulse. Therefore, if the auxiliary voltage pulse is not used except at the time of use at a high temperature where unnecessary ink droplets are likely to be generated after continuous ejection, there is an advantage that an unnecessary decrease in printing speed can be avoided.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram mainly showing a control system of an ink jet printer to which the present invention is applied.
FIG. 2 is a schematic sectional view illustrating a configuration example of an inkjet head of the inkjet printer of FIG.
FIG. 3 is a schematic block diagram showing an internal configuration of a head driver IC in FIG. 2;
FIG. 4 is a timing chart showing signal waveforms of respective units in 2 shot / dot driving in the inkjet printer of FIG. 1;
FIG. 5 is a timing chart showing signal waveforms of respective units in 3 shot / dot driving in the inkjet printer of FIG. 1;
FIG. 6 is a timing chart showing signal waveforms of respective units in 4 shot / dot driving in the ink jet printer of FIG. 1;
FIG. 7 is a timing chart showing signal waveforms of various parts in 6 shot / dot driving in the inkjet printer of FIG. 1;
FIG. 8 shows waveforms of a driving voltage pulse and an auxiliary voltage pulse in a driving control mode in which an auxiliary voltage pulse is applied after a plurality of ink droplet ejections to prevent unnecessary ink droplet ejection in the ink jet printer of FIG. FIG.
FIG. 9 is a timing chart showing signal waveforms of various parts in 2 shot / dot driving in the inkjet printer of FIG. 1;
FIG. 10 is a timing chart showing signal waveforms of respective units in 3 shot / dot driving to which an auxiliary voltage pulse is added in the inkjet printer of FIG. 1;
11 is a timing chart showing a timing chart showing a signal waveform of each unit in 4 shot / dot driving to which an auxiliary voltage pulse is added in the inkjet printer of FIG. 1;
FIG. 12 is a timing chart showing signal waveforms of various parts in 6-shot / dot drive to which an auxiliary voltage pulse is added in the ink jet printer of FIG. 1;
FIG. 13 is an explanatory diagram showing a head rank related to a pulse width in the inkjet printer of FIG. 1;
FIG. 14 is an explanatory diagram showing a head rank of the number of ejections in a 6-shot / dot print mode in the inkjet printer of FIG. 1;
FIG. 15 is a graph showing variations in the ink ejection mass when the number of ejections is calculated based on the number of ejections head rank in the inkjet printer of FIG. 1 and variations in the conventional ink ejection mass.
FIG. 16 is an explanatory diagram showing a relationship between a head rank and the number of ejections (the number of shots) in a 6-shot / dot printing mode in the inkjet printer of FIG. 1;
FIG. 17 is an explanatory diagram showing a problem in multi-shot driving.
[Explanation of symbols]
1 inkjet head drive control device
2 Inkjet head controller
6. Drive pulse generation circuit
8 Head substrate
9 Head driver IC
12. Shot rank identification circuit
13 Pulse width rank identification circuit
14. Shot rank detection circuit
15 Pulse width rank detection circuit
16 Thermistor
17 Temperature detection circuit
100 inkjet head
105 ink nozzle
106 ink chamber
107 diaphragm (common electrode)
109 Individual electrode (counter electrode)
V3 drive voltage pulse signal
V3h auxiliary voltage pulse
LP control signal
REV inversion control signal
T 1 pixel printing period

Claims (14)

In a drive control method for an inkjet head, a drive voltage pulse is applied to an electrostatic actuator to eject ink droplets from an ink nozzle, and printing for one pixel is formed by ejecting ink droplets one or more times.
When performing printing for one pixel by ejecting ink droplets a smaller number of times than the number of ejections of ink droplets included in one pixel printing period, it is necessary to perform a continuous ink droplet ejection operation. Characteristic drive control method of an ink jet head. In claim 1,
A drive control method for an ink-jet head, wherein the number of ejections of ink droplets for printing one pixel is changed to control the gradation of the pixel. In claim 1,
Detecting a head rank related to the number of ejections of ink droplets set in advance,
A drive control method for an ink jet head, comprising: calculating a number of ejections of ink droplets for forming one print pixel based on a detected head rank related to the number of ejections detected. In claim 1, 2 or 3,
In the case where one pixel is printed by continuous ink droplet ejection, the last ink droplet ejection is set as the last ink droplet ejection time of one pixel printing period. Method. In claim 4,
After performing continuous ejection of ink droplets for printing one pixel, an auxiliary voltage pulse for preventing unnecessary ink droplets from being ejected from the ink nozzle is applied to the electrostatic actuator. Drive control method for an inkjet head. In claim 5,
Detecting the ambient temperature of the inkjet head,
A drive control method for an ink-jet head, wherein the auxiliary voltage pulse is applied only when the ambient temperature is equal to or higher than a predetermined value. In any one of claims 1 to 6,
In the case where printing for one pixel is performed by ejecting ink droplets a plurality of times, the drive voltage pulse of which polarity is alternately applied is applied to the electrostatic actuator, and a drive control method for an ink jet head is provided. . An ink nozzle for ejecting ink droplets,
An ink chamber communicating with the ink nozzle and holding ink;
An electrostatic actuator including a vibration plate elastically displaceable in an out-of-plane direction forming a part of the ink chamber and a counter electrode arranged to face the vibration plate at a predetermined interval,
An inkjet head drive control device for applying a drive voltage pulse to the electrostatic actuator to eject ink droplets from the ink nozzles and forming a print for one pixel by ejecting ink droplets one or more times; Has,
The ink jet head drive control device is configured to print a continuous ink liquid when one pixel is printed by ejecting ink droplets a smaller number of times than the number of ink droplet ejections included in one pixel printing period. An ink jet printer comprising a driving voltage pulse generating means for generating the driving voltage pulse for performing a droplet discharging operation. In claim 8,
An ink jet printer, wherein the ink jet head drive control device controls the gradation of the pixel by changing the number of ejections of ink droplets for printing one pixel. In claim 8,
The inkjet head drive control device,
A discharge rank head rank setting unit in which a head rank relating to the discharge count for forming one pixel of printing is set;
A discharge count calculating unit that calculates a discharge count of ink droplets for forming one print pixel based on a head rank related to the discharge count set in the discharge count head rank setting unit;
An ink jet printer, wherein the drive voltage pulse generating means generates the drive voltage pulse for forming one pixel of a print at the calculated number of ejections. In any one of claims 8 to 10,
The drive voltage pulse generating means sets the ejection of the last ink droplet to the ejection point of the last ink droplet in one pixel printing period when printing one pixel by continuous ejection of ink droplets. An ink jet printer that generates a voltage pulse. In claim 11,
The driving voltage pulse generating means generates an auxiliary voltage pulse for preventing unnecessary ink droplets from being ejected from the ink nozzles after performing continuous ejection of ink droplets for printing one pixel. An ink jet printer, characterized in that: In claim 12,
Having a temperature detecting means for detecting the ambient temperature of the inkjet head,
The ink-jet printer according to claim 1, wherein the driving voltage pulse generating means generates the auxiliary voltage pulse only when an ambient temperature is equal to or higher than a predetermined value. In any one of claims 8 to 13,
An ink jet printer, wherein the drive voltage pulse generating means generates the drive voltage pulse whose polarity is alternately reversed when printing of one pixel is performed by discharging ink droplets a plurality of times.

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