JPH08156244A - Ink jet printer - Google Patents

Abstract

PURPOSE: To realize stable recording by controlling the amt. of emitted ink droplets when ink droplets are emitted to perform printing. CONSTITUTION: An ink jet printer is equipped with an emitting part constituted of nozzles and electrothermal conversion means, a supply part B supplying a pulse electric signal to the electrothermal conversion means, a control part C and an emitting history memory part D storing the emitting history of the emitting part A. The pulse signal applied to the electrothermal conversion means is divided into blocks with predetermined width and ON/OFF at every blocks is controlled to control the amts. of emitted ink droplets. Therefore, stable printing quality can be obtained regardless of printing history and environment temp. Further, multigradation in a dot unit is enabled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer used for output printing of office computers, personal computers and the like, and more particularly, a thermal ink jet printer which causes thermal boiling of ink to cause ink boiling. It concerns printers.

[0002]

2. Description of the Related Art FIG. 20 is a block diagram of an ink ejecting portion of a conventional ink jet printer. This is described, for example, in US Pat. No. 3,179,042. In FIG. 20, 1 is a conductive ink, 2 is an ink chamber filled with the conductive ink 1, 3 is an ink tank containing the conductive ink 1, and 4 and 5 are a pair arranged below the liquid surface of the conductive ink. , 6 is a power source, 7 is a switch for the power source 6, 8 is a nozzle for ejecting the conductive ink 1, 9 is a surface to be printed, and 10 is an ink droplet ejected from the nozzle 8. When a voltage is applied to the pair of electrodes 4 and 5, a current flows through the conductive ink 1, and the Joule heat causes a part of the conductive ink 1 between the tips of the electrodes 4 and 5 to vaporize. Further, the vaporized vapor of the conductive ink 1 is discharged from the nozzle 8 to the surface 9 to be printed.
The ink is expanded until sufficient pressure is generated to eject the ink droplet 10. By selecting the electrode to which the voltage is applied by the switch 7, the nozzle hole for ejecting the conductive ink 1 is selected so that a desired character can be formed on the surface 9 to be printed.

[0003]

However, in the conventional ink ejecting section, the change in the ink temperature due to the change in the outside air temperature may affect the recording. That is, since the viscosity of the ink remarkably increases as the temperature decreases,
At low temperature, the diameter of the boiling bubble became small, the amount of ink droplets ejected from the nozzle decreased, and the print quality deteriorated due to satellite or splash. In addition, there is a problem that the amount of ink ejected droplets changes due to heat storage of ink due to continuous boiling. Further, since the density of dots themselves cannot be multi-graded in the conventional inkjet printer, when printing a natural image such as a photograph, the number of dots in a square lattice of n × n dots is increased or decreased depending on the brightness of the original image. Multi-gradation printing was realized by a method such as a method. However, in this method, for example, 4 × 4 for 16 gradations and 8 × 8 for 64 gradations are required. To obtain more gradations, it is necessary to use a large square grid, so that the resolution There was a problem that it was difficult to achieve both gradations.

Therefore, an object of the present invention is to provide an ink jet printer which can control the amount of ink ejected from a nozzle and can perform stable printing.

[0005]

To this end, an ink jet printer according to the present invention includes a nozzle for ejecting a liquid, a liquid passage communicating with the nozzle, an electrothermal converting means provided in the liquid passage, and a pulsed electric device. A supply means for intermittently supplying a signal to the electrothermal conversion means to generate thermal energy capable of forming flying droplets and discharging the liquid from a nozzle, and a pulsed electric signal divided into blocks each having a predetermined width A control unit for controlling each pulse electric signal block and a print history storage unit for storing the print history of the nozzle, and the liquid discharged from the nozzle based on the history data stored in the print history storage unit. Control was performed for each pulse electric signal block so as to keep the drop amount constant.

Further, a temperature detecting means for detecting the temperature around the nozzle is provided, and based on the temperature detected by the temperature detecting means,
Control was performed for each pulse electric signal block so that the amount of liquid droplets ejected from the nozzle was kept constant.

Further, the amount of liquid droplets ejected from the nozzle is changed by controlling each pulse electric signal block.

Further, a nozzle for ejecting a liquid, a liquid path filled with the conductive ink and communicating with the nozzle, a plurality of ejection portions formed of a pair of electrodes provided in the liquid path, and a pulse voltage applied between the electrodes. A supply means for supplying and a control means for controlling each pulse electric signal block by dividing into blocks having a predetermined width are provided, and the electrodes are shared by the adjacent ejecting portions and reverse to any pair of electrodes. Supplying a pulse voltage of the phase, energizing the conductive ink between the electrodes with an alternating current, heating and boiling to eject the ink due to the generated pressure of the boiling bubbles and perform the energized ink ejection for printing,
A pulse voltage of the same phase was supplied between the electrodes that did not discharge.

[0009]

According to the present invention, it is possible to realize an ink jet printer capable of high-quality printing regardless of the heat storage of ink in the liquid passage communicating with the nozzle and the change of the outside air temperature. Further, by controlling the print dot diameter, it is possible to realize an inkjet printer with high resolution and multiple gradations.

[0010]

Embodiments of the present invention will be described below. FIG. 1 is a configuration diagram of an ink ejection device of an inkjet printer according to a first embodiment of the present invention. Reference symbol A is a discharge unit including a nozzle and electrothermal conversion means, B is a supply unit that supplies a pulse electric signal to the electrothermal conversion unit of the discharge unit A, C is a control unit that controls the supply unit B, and D is a discharge unit. A discharge history storage unit that stores the discharge history of A, S1 is a print data signal, S2 is a print start signal, a, b, c, d are control signals of the supply unit, and P
1, P2 are pulse electric signals, and H1 to H8 are signals.

FIG. 2 is a configuration diagram of an ink ejecting portion of an ink jet printer according to the first embodiment of the present invention, and FIG. 3 is a relational diagram of input energy and ejected droplet amount per unit time for conductive ink of the ink jet printer. is there.
In FIG. 2, 13 is a nozzle for ejecting ink, 14 is an ink liquid path, 15 is conductive ink, 16 is an ink tank for supplying the conductive ink 15 to the nozzle 13, 17, 18
Is an electrode for energizing the conductive ink 15, and by supplying pulse electric signals P1 and P2 to the electrodes 17 and 18 from the supply unit B alternately, a current I flows in both directions through the conductive ink 15. The conductive ink 15 generates heat and boils due to the resistance component, and the ink is ejected from the nozzle 13. At this time, the current is passed in both directions in order to suppress the wear due to the electrolysis of the electrodes 17 and 18 due to the direct current. In addition, the conductive ink 1 per unit time at this time
There is a characteristic shown in FIG. This is because the heat generated by energizing is conducted from the vicinity of the electrodes 17 and 18 to the periphery thereof, but when the input energy per unit time is large,
Since it is heated rapidly, only a small portion of the conductive ink 15 near the electrodes 17 and 18 boils before the heat propagates to the conductive ink 15 in the surroundings, so that the boiling bubbles generated do not become so large. Therefore, the amount of liquid droplets ejected from the nozzle 13 is also small, and conversely, when the input energy per unit time is small, the conductive ink 15 is slowly heated, so that heat propagates to the outer conductive ink 15, This is because the amount of ink that boils increases, the boiling bubbles increase, and the amount of ejected droplets also increases. Therefore, the electrodes 17, 18
It is possible to control the discharge droplet volume by dividing the pulse electric signal applied to the block into blocks and controlling this pulse signal block to turn on and off and equivalently increase or decrease the input energy per unit time. Becomes

FIG. 4 is a block diagram of the supply unit of the ink jet printer in the first embodiment of the present invention. 19, 20
Is a current source type drive circuit, 21 and 22 are current sink type drive circuits, 17 and 18 are electrodes of the ink ejection portion A, R is an ink resistance of the conductive ink 15, 23, 24, 25 and 26 are AND gates, 27 , 28 are NOT gates, a, b,
c and d are control signals given from the control unit C. When the logic levels of the control signals c and d are L, the current source type drive circuits 19 and 2 are irrespective of the logic levels of the control signals a and b.
0 and the current sink type drive circuits 21 and 22 are off, and the electrodes 17 and 18 are in a high impedance state. When the logic levels of the control signals c and d are H and the logic levels of the control signals c and d are H and L, respectively, the current source drive circuit 1
9. The current sink type drive circuit 22 is turned on, the current source type drive circuit 19 and the current sink type drive circuit 22 are turned off, and the current I1 flows through the ink resistance R. When the logic levels of the control signals c and d are H and the logic levels of the control signals c and d are L and H, respectively, the current source drive circuit 1
9. The current sink type drive circuit 22 is turned off, the current source type drive circuit 19 and the current sink type drive circuit 22 are turned on, and the current I2 flows through the ink resistance R.

FIG. 5 is a block diagram of the ejection history storage section of the ink jet printer in the first embodiment of the present invention. The print data signal S1 is sequentially input to the shift register 29 by the print timing signal S2, and serially connected to H1 to H8.
Converted in parallel. H1 to H8 are input to the control unit C as history data indicating the ejection history up to the last eight.

FIG. 6 is a block diagram of the control unit of the ink jet printer in the first embodiment of the present invention, and FIG. 7 is a timing chart of the operation of the control unit of the ink jet printer. In FIG. 6, H1 to H8 are ejection history data generated in the ejection history storage unit D, 31 is a printing time counter 33 corresponding to the ejection history data H1 to H8 input in advance,
A memory in which initial values of the cutoff period counter 34 and the pulse block counter 35 are stored, 32 is a clock signal generation unit, 33 is a printing time counter for determining the application time of the pulse electric signal to the electrodes 17 and 18, and 35 is a pulse. A pulse block counter for determining blocks of electrical signals, 34
Is a cutoff cycle counter that determines the cutoff time of the pulse block, 36 is a pulse generation circuit that generates energization pulses, 3
7, 38 and 39 are AND gates, 40 is an output signal of the pulse block counter 35, 41 is a cutoff period counter 34
, 42 is an output signal of the printing time counter 33,
Reference numeral 43 is a clock signal output from the clock signal generator 32, and a, b, c and d are control signals.

The operation of the controller C will be described below with reference to the timing chart of FIG. In this example, the initial values of the print time counter 33, the cutoff period counter 34, and the pulse block counter 35 are 8, 2, and 7, respectively.

When the print data signal S1 is at H level and the print start signal S2 is input, the print time counter 33, the cutoff period counter 34, and the pulse block counter 35 preset load the initial values generated by the memory 31, respectively.
Count down. The pulse block counter 35 circulates from 8 to 0, and the counter value 8 to 1 is output from the output signal 40.
When the counter value is 0, the H level is output, and when the counter value is 0, the L level is output. The cutoff cycle counter 34 circulates 2 to 0 at the rising edge of the output signal 40, and the output signal 41 outputs H level when the counter value is 2 to 1 and L level when the counter value is 0. The print time counter 33 counts down from the initial value at the rising edge of the output signal 40, and the output signal 4
2 has an H level until the counter value is 0, and has an L level when the counter value is 0. The pulse generation circuit 36 uses the clock signal 4
3 is divided and pulse signals 43 and 44 having a phase of 180 degrees are output. Then, by the AND gates 37, 38, 39, the control signals a, b, c, d shown in the timing example of FIG.
Is output.

FIG. 8 is a diagram showing the relationship between the printing frequency of nozzles and the amount of discharged liquid droplets of the ink jet printer according to the first embodiment of the present invention. FIG. 9 is a timing chart of the ink jet printer. There is a tendency that heat is accumulated, the boiling bubbles become large, and the discharge amount increases. In the present embodiment, as shown in FIG. 9, the ink liquid passage 14 is normally formed by the respective parts configured as described above.
If the ink inside is not accumulating heat, a pulse electric signal with a short interruption period for turning off the energization pulse block is applied to the electrodes 17 and 18 of the ejection portion A, and the ink accumulates heat according to the past printing history. In the case where the size of the boiling bubble is increased, a pulsed electric signal having a long interruption period for turning off the energization pulse block is applied to the electrodes 17 and 18 of the ejection portion A to rapidly heat the energized pulse block according to the degree of heat storage. By suppressing the effect of increasing the diameter of the boiling bubble due to heat storage by the suppressing effect, the amount of discharged droplets can be made uniform and stable printing quality can be realized.

FIG. 10 is a block diagram of the control unit of another ink jet printer in the first embodiment of the present invention, and FIG. 11 is a timing chart of the same operation. In the embodiment described above, the pause period included in the energization pulse block is in the high impedance state, but as shown in FIG. 10, the output signal 42 of the printing time counter 33 and the output signal 41 of the cutoff period counter 34 are supplied to the AND gate 46. By inputting and outputting signals c and d, it is also possible to control the idle period included in the energization pulse block to the GND level as shown in FIG.

Next, a second embodiment of the present invention will be described. FIG.
2 is a configuration diagram of an ink ejection device of an ink jet printer in a second embodiment of the present invention, FIG. 13 is a relationship diagram between the same environmental temperature and the amount of ejected liquid droplets, and FIG. 14 is the same timing chart. The configuration of the ink ejection device shown in FIG. 12 is the same as that of the ejection history storage unit D shown in FIG.
7, the data stored in advance in the memory 31 shown in FIG. 6 is changed to the initial values of the print time counter 33, the cutoff cycle counter 34, and the pulse block counter 35 according to the environmental temperature.

The temperature detector 47 detects the environmental temperature and converts it into temperature data H1 to H8. As shown in FIG. 13, the change in the amount of discharged ink droplets with respect to the environmental temperature tends to increase as the environmental temperature rises. Therefore, as shown in FIG. Is applied to the electrodes 17 and 18 of the ejection portion A with a short cut-off cycle for turning off the energization pulse block, and when the environmental temperature is high, a pulse with a long cut-off cycle for turning off the energization pulse block is applied. By applying an electric signal to the electrodes 17 and 18 of the ejection part A to rapidly heat the same, the effect of suppressing the size of the boiling bubble is offset, and the effect of increasing the diameter of the boiling bubble due to the increase in the environmental temperature is offset, thereby achieving the ejection. It is possible to realize a stable print quality by making the droplet amount uniform.

Next, a third embodiment of the present invention will be described. FIG.
5 is a configuration diagram of an ink ejection device of an ink jet printer in a third embodiment of the present invention, and FIG. 16 is a timing chart of the ink ejection device. In the configuration of the ink ejection device of the third embodiment, the print data H1 to H8 having gradation as shown in FIG. 15 is input to the control unit C and stored in advance in the memory 31 of the control unit C shown in FIG. Printing time counter 33 and cutoff cycle counter 3 according to the gradation data
4. It can be realized by changing the initial value of the pulse block counter 35. That is, as shown in FIG. 16, in order to obtain high-density printing, a pulse electric signal with a short interruption period for turning off the energization pulse block is applied to the electrodes 17 and 18 of the ejection portion A to increase the boiling bubble diameter. In order to increase the amount of ejected ink droplets and to obtain a print with a low density, the pulsed electric signals with a long interruption period for turning off the energization pulse block are applied to the electrodes 17, 18 of the ejection unit A.
By controlling the amount of the ejected ink droplets by controlling the size of the boiling bubble by rapidly applying the applied voltage to the ink, it is possible to express gradation in print dot units.

FIG. 17 is a block diagram of an ink ejection device of an ink jet printer according to a fourth embodiment of the present invention, and FIG.
Is a configuration diagram of a supply unit of the ink ejecting apparatus, and FIG. 19 is a timing chart of the ink ejecting apparatus. In FIG. 17, reference numeral 48 is a discharge part composed of a nozzle and electrothermal converting means, 49 is a supply part for supplying a pulse electric signal to the electrothermal converting means of the discharge part 48, 50 is a control part for controlling the supply part 49, S1 is a print data signal, S2 is a print start signal, 51
Reference numerals 62 to 62 are control signals for the supply unit, and 63 to 68 are pulse electric signals.

In FIG. 18, 163 to 168 are current source type drive circuits, 69 to 74 are current sink type drive circuits,
75 to 86 are AND gates, 87 to 92 are NOT gates, 93 to 98 are electrodes of the ink ejection portion 48, and R1 to R5.
Is an ink resistance of the conductive ink, and 51 to 62 are control units 50.
This is a control signal given by

When the logic levels of the control signals 51 to 56 are L, the current source type drive circuits 163 to 168 and the current sink type drive circuits 69 to 74 are off and the electrodes 93 are irrespective of the logic levels of the control signals 57 to 62. ~ 98 is in a high impedance state. The logic levels of the control signals 51 to 56 are H, and the logic levels of the control signals 57 to 62 are L, respectively.
In the case of, the current source type drive circuits 163-168 are off,
The current sink type drive circuits 69 to 74 are turned off, the logic levels of the control signals 51 to 56 are H, and the control signals 57 to 62 are
, The current source type drive circuits 163 to 168 are on, and the current sink type drive circuits 69 to 168.
74 is turned on. Therefore, for example, by turning on the current source type drive circuit 163 and the current sink type drive circuit 70, the current I3 causes the ink resistance R1 between the electrodes 93 and 94.
Flowing through. Others are the same.

Next, the timing chart of this embodiment will be described. In FIG. 19, energizing pulse blocks T1, T2
Then, a current flows through the ink resistances R1, R3, R5 between the electrodes 93 and 94, the electrodes 95 and 96, and the electrodes 97 and 98 whose output levels are 180 degrees in phase. In the energization pulse block T3, the electrode 9 whose output level phase is 180 degrees is used.
Current flows through the ink resistors R1 and R5 between the electrodes 3 and 94 and the electrodes 97 and 98. Further, since the electrodes 95 and 96 have high impedance, when the phase of the output level of the electrodes 94 and 97 is 180 degrees, current flows through R2 to R4.
Here, since the output levels of the electrodes 94 and 97 are in phase with each other, no current flows through R2 to R4. In the energization pulse blocks T4 and T5, the phase of the electrode output level is 180
Therefore, the current flows through the ink resistances R1, R3 and R5 as in the energization pulse blocks T1 and T2.

In this way, when the energizing pulse is applied to the plurality of ejecting portions and the energizing pulse block is turned on / off to individually control the amount of ink droplets ejected from the ejecting portion, the ejection is performed. Only the phase of the energizing pulse between the electrodes of the discharge part is set to the opposite phase, and the phase between the electrodes that are not related to other discharge is controlled to be the same phase, and only the conductive ink between the electrodes of the discharge part that discharges is controlled. By allowing an electric current to flow, stable boiling can be performed and stable printing can be obtained. Further, in the present embodiment, since the energization pulse block has the quiescent period, the quiescent period enters the phase change point, so that the period of the energizing pulse can always be made constant.

[0027]

As described above, according to the present invention, it is possible to realize an ink jet printer which can always perform stable and high quality printing regardless of the printing frequency of nozzles. Further, it is possible to realize an ink jet printer which can always perform stable and high-quality printing regardless of changes in environmental temperature. Furthermore, since it is possible to perform multi-gradation printing for each nozzle, it is possible to inexpensively realize a high-resolution and multi-gradation inkjet printer, and it is possible to prevent current from flowing to an ejection unit that does not eject. Stable boiling can be performed and high quality printing can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an ink ejection device of an inkjet printer according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of an ink ejection unit of the inkjet printer according to the first embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between the input energy and the amount of discharged liquid droplets per unit time for the conductive ink of the inkjet printer according to the first embodiment of the present invention.

FIG. 4 is a configuration diagram of a supply unit of the inkjet printer according to the first embodiment of the present invention.

FIG. 5 is a configuration diagram of an ejection history storage unit of the inkjet printer according to the first embodiment of the present invention.

FIG. 6 is a configuration diagram of a control unit of the inkjet printer according to the first embodiment of the present invention.

FIG. 7 is a timing chart of the operation of the control unit of the inkjet printer according to the first embodiment of the present invention.

FIG. 8 is a diagram showing the relationship between the printing frequency of nozzles and the amount of discharged liquid droplets in the inkjet printer according to the first embodiment of the present invention.

FIG. 9 is a timing chart of the inkjet printer according to the first embodiment of the present invention.

FIG. 10 is a configuration diagram of a control unit of another inkjet printer according to the first embodiment of the present invention.

FIG. 11 is a timing chart of the operation of the control unit of another inkjet printer according to the first embodiment of the present invention.

FIG. 12 is a configuration diagram of an ink ejection device of an inkjet printer according to a second embodiment of the present invention.

FIG. 13 is a diagram showing the relationship between the environmental temperature of the ink ejecting apparatus of the ink jet printer and the ejected liquid droplet amount in the second embodiment of the present invention.

FIG. 14 is a timing chart of the ink ejection device of the inkjet printer according to the second embodiment of the present invention.

FIG. 15 is a configuration diagram of an ink ejection device of an inkjet printer according to a third embodiment of the present invention.

FIG. 16 is a timing chart of an ink ejection device of an inkjet printer according to a third embodiment of the present invention.

FIG. 17 is a configuration diagram of an ink ejection device of an inkjet printer according to a fourth embodiment of the present invention.

FIG. 18 is a configuration diagram of a supply unit of an ink ejection device of an inkjet printer according to a fourth embodiment of the present invention.

FIG. 19 is a timing chart of an ink ejection device of an inkjet printer according to a fourth embodiment of the present invention.

FIG. 20 is a configuration diagram of an ink ejection unit of a conventional inkjet printer.

[Explanation of symbols]

 A ejection unit B supply unit C control unit D ejection history storage unit S1 print data signal S2 print start signal a, b, c, d control signal P1, P2 pulse electric signal 13 nozzle 14 ink liquid path 15 conductive ink 16 ink tank 17, 18 Electrodes 19, 20 Current source type drive circuit 21, 22 Current sink type drive circuit 23, 24, 25, 26 AND gate 27, 28 NOT gate 29 Shift register 30 AND gate 31 Memory 32 Clock signal generator 33 Printing time Counter 34 Cutoff period counter 35 Pulse block counter 36 Pulse generation circuit 37, 38, 39 AND gate 47 Temperature detector

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location B41J 3/04 104 F (72) Inventor Shinsuke Sato 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. In-house (72) Inventor Akihiro Yamashita 1006 Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (7)

[Claims] 1. A nozzle for discharging a liquid, a liquid path communicating with the nozzle, an electrothermal converting means provided in the liquid path, and a pulsed electric signal intermittently supplied to the electrothermal converting means. Supplying means for generating thermal energy capable of forming flying droplets and discharging the liquid from the nozzle, and controlling the pulse electric signal block by dividing the pulse electric signal into blocks each having a predetermined width Control means to perform,
A print history storage unit for storing the print history of the nozzle, and the pulse electric signal block for keeping the amount of droplets discharged from the nozzle constant based on the history data stored in the print history storage unit. An inkjet printer characterized by performing control for each. 2. The high-impedance idle period is included in the pulse electric signal block.
The described inkjet printer. 3. The ink jet printer according to claim 1, wherein the pulse electric signal block includes a GND level idle period. 4. A nozzle for discharging a liquid, a liquid path communicating with this nozzle, an electrothermal converting means provided in this liquid path, and a pulsed electric signal which is intermittently supplied to the electrothermal converting means. Supplying means for generating thermal energy capable of forming flying droplets and discharging the liquid from the nozzle, and controlling the pulse electric signal block by dividing the pulse electric signal into blocks each having a predetermined width Control means to perform,
A temperature detecting means for detecting the temperature around the nozzle, and performing control for each pulse electric signal block so as to keep the amount of liquid droplets ejected from the nozzle constant based on the temperature detected by the temperature detecting means. Inkjet printer characterized by. 5. A nozzle for discharging a liquid, a liquid passage communicating with this nozzle, an electrothermal converting means provided in this liquid passage, and a pulsed electric signal intermittently supplied to the electrothermal converting means. Supplying means for generating thermal energy capable of forming flying droplets and discharging the liquid from the nozzle, and controlling the pulse electric signal block by dividing the pulse electric signal into blocks each having a predetermined width An ink jet printer, comprising: a control unit that performs the control, and changing the amount of liquid droplets ejected from the nozzle by performing control for each of the pulse electric signal blocks. 6. The control means divides the pulse signal into blocks each having a predetermined width according to the gradation of image data to be printed, and controls each pulse electric signal block, 6. The ink jet printer according to claim 5, wherein the print dot diameter is changed by changing the amount of liquid droplets ejected from the nozzle by performing control for each pulse electric signal block. 7. A nozzle for ejecting a liquid, a liquid path filled with a conductive ink and communicating with the nozzle, a plurality of ejecting portions provided in the liquid path, each having a pair of electrodes, and a pulse between the electrodes. A supply means for supplying a voltage and a control means for controlling a pulsed electric signal for each block having a predetermined width are provided, and the electrodes are shared by adjacent ejection parts and have opposite phases to any pair of the electrodes. Pulse current is applied to the conductive ink between the electrodes to heat and boil the ink, and the generated pressure of the boiling bubbles causes the ink to fly to perform printing. An inkjet printer characterized in that pulse voltages of the same phase are supplied between electrodes that are not used.