JP3511766B2 - Driving method of ink jet head and ink jet printer using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of driving an ink jet head which ejects ink droplets by changing the volume of an ink chamber communicating with an ink nozzle and uses the same.
And an inkjet printer .

More specifically, the present invention relates to a method of driving an ink jet head which can appropriately perform a preliminary ejection operation which is performed prior to an ink droplet ejection operation for actual printing.

[0003]

2. Description of the Related Art As an ink jet head, in addition to a type in which a heating element is used to induce a volume change of ink to eject an ink droplet, an ink chamber connected to an ink nozzle which is the object of the present invention is used. A type is known in which ink droplets are ejected by changing the volume.

As an ink jet head to which the present invention is applied, for example, an electromechanical conversion element such as a piezoelectric element may be used as disclosed in Japanese Patent Publication No. 2-24218. Also, for example, US Pat.
As disclosed in the specification of No. 75 and Japanese Patent Application Laid-Open No. 5-50601, there is one that displaces a diaphragm forming a part of an ink chamber by using electrostatic force.

As the ejection driving mode of ink droplets in these ink jet heads, modes called "push ejection" method and "pull ejection" method are known.
The push-out method reduces the volume of the ink chamber when the ink meniscus rests at the ink nozzle opening after displacing a displacement plate such as a vibration plate that is formed in a part of the ink chamber in the direction of increasing the volume of the ink chamber. By displacing the displacement plate in such a direction, ink droplets are ejected from the ink nozzles. On the other hand, the pulling-out method is as described in Japanese Patent Publication No. 2-24218 mentioned above.
When the displacement plate is displaced in the direction in which the volume of the ink chamber decreases, and in this state the displacement plate is displaced in the direction in which the volume of the ink chamber increases, the ink meniscus is drawn in from the nozzle opening, and when the ink meniscus is most drawn in. By displacing the displacement plate in the opposite direction, ink droplets are ejected from the ink nozzles.

Here, in the ink jet head, when the non-use period of the nozzle becomes long, the solvent of the ink filled therein evaporates from the nozzle opening and the ink viscosity becomes high. For this reason, when ejecting ink droplets for printing characters and the like, the ink viscosity increases and the natural frequency of the ink in the ink chamber fluctuates. Therefore, the preset drive voltage pulse is applied to the nozzle portion to be driven. There is a case where an appropriate ejection operation cannot be immediately performed even when the voltage is applied to. That is, there are cases in which the amount of ink droplets that are ejected is small and dot printing of an appropriate size cannot be formed. Such an adverse effect may occur in an inkjet head having a large number of nozzles, even in a printing operation, in a nozzle that is rarely used.

In order to avoid this adverse effect, conventionally, the ink jet head is moved to a position away from the printing position before the start of printing or even during printing, so that each ink nozzle is moved. By driving, the ink droplets are wastefully ejected, that is, the preliminary ejection operation is performed a fixed number of times. Such preliminary ejection is disclosed in, for example, Japanese Patent Publication No. 4-64311 and Japanese Patent Publication No. 6-39163.

[0008]

In the conventional driving method for preliminary ejection, the ejection of ink droplets is not properly performed, and the state of each nozzle is set to a state suitable for actually printing characters and the like. May not be able to recover up to.
In the driving method disclosed in Japanese Patent Publication No. 6-39163, the head driving frequency at the time of preliminary ejection is lower than the frequency at the time of printing a normal character, and the driving frequency is stepwise. Or continuously increase. However, such a method of changing the driving frequency may not be suitable for an inkjet head of a type that ejects ink droplets by vibrating the diaphragm of the ink chamber by using electrostatic force.

An object of the present invention is to propose a method of driving an ink jet head, which is capable of performing a preliminary ejection drive properly to surely recover an ink nozzle.

In particular, an object of the present invention is to provide an ink jet head of a type which discharges ink droplets by vibrating a vibrating plate forming a part of an ink chamber communicating with an ink nozzle by utilizing electrostatic force. It is to propose a driving method suitable for preliminary ejection driving.

[0011]

In order to solve the above-mentioned problems, the present invention provides a nozzle, an ink chamber communicating with the nozzle, a displacement plate provided with a part of the ink chamber, and a drive pulse. The displacement of the displacement plate using a voltage changes the volume of the ink chamber to eject ink droplets from the nozzles, and in an inkjet head that prints characters and the like with the ejected ink droplets, nozzle recovery is performed. The ejection of each ink droplet in the preliminary ejection drive is performed by a push-push method.

That is, in the preliminary ejection drive of ink droplets for recovering the nozzle, the displacement plate is displaced in the direction in which the volume of the ink chamber increases, and the nozzle moves in accordance with the increase of the volume. When the ink meniscus is once drawn back and then returns to the opening position of the nozzle in a substantially stationary state, the displacement plate is displaced in the direction in which the volume of the ink chamber decreases.

Further, in the method of the present invention, the ejection drive for printing the ink droplets for printing characters and the like is performed by a pulling method. That is, the displacement plate is displaced in the direction in which the volume of the ink chamber increases, and when the ink meniscus of the nozzle is substantially pulled in as the volume increases, the displacement plate is moved to the volume of the ink chamber. Is performed by displacing in the direction of decreasing.

In the above-described pulling-out method, since kinetic energy in the displacement direction of the displacement plate is also used as the ejection energy of ink droplets, a large amount of ink droplets can be ejected at a higher speed than in the pushing-out method. You can In the present invention, since this method is adopted for the usual ink droplet ejection drive for printing characters and the like, it is possible to realize stable and high-speed dot printing of ink droplets.

On the other hand, since the above-mentioned pushing method does not substantially utilize the kinetic energy of the displacement plate,
The ejection amount and ejection speed of ink droplets are generally inferior to those of the ejection method. However, the characteristics of the ink in the ink chamber, in particular, the ejection characteristics of the ink droplets do not change due to changes in the dynamic characteristics that accompany changes in the viscosity.
In other words, unlike the ejection method, the ejection characteristics of the ink droplets do not deteriorate due to changes in the dynamic characteristics that accompany changes in the viscosity of the ink. In the present invention, this method is adopted for the preliminary ejection drive in which the ejection operation of the ink droplets is performed in the state where the ink viscosity is increased. Therefore, appropriate ink droplets can always be ejected without being affected by fluctuations in ink viscosity, and the nozzle can be reliably returned to the recovery state.

Here, the change in the ejection characteristic of the ink droplet due to the fluctuation of the ink viscosity as described above is particularly caused by vibrating the vibrating plate forming a part of the ink chamber by utilizing the electrostatic force. This is remarkable in an inkjet head that ejects ink droplets. Therefore, the method of the present invention is suitable for use as a method of driving this type of inkjet head.

Further, in an ink jet head which ejects ink droplets by vibrating the vibrating plate by using electrostatic force, residual electric charge is generated between the vibrating plate and a counter electrode facing the vibrating plate. If the residual charge is generated, the vibration characteristics of the vibration plate fluctuate, and an appropriate ink droplet ejection operation cannot be performed. Therefore, during the preliminary ejection drive, it is desirable to apply a drive voltage pulse having a polarity opposite to the polarity of the drive voltage pulse applied during the drive for printing characters and the like. By doing so, the residual charge is removed together with the nozzle recovery operation during the preliminary ejection drive. Therefore, it is possible to always perform the ejection operation for printing characters and the like performed thereafter in an appropriate state. Na
The inkjet printer of the present invention includes the above-mentioned drive units.
It is a printer that adopts the operating method, and the same items as each method
Is specified in.

[0018]

DETAILED DESCRIPTION OF THE INVENTION A method of driving an inkjet head to which the present invention is applied will be described below with reference to the drawings.

First, FIG. 1 is a schematic diagram of an ink jet printer to which the present invention is applied. The overall structure of the ink jet printer 310 of this example is a general one. The platen 300 that conveys the recording paper 105 and the platen 30
The inkjet head 10 facing 0, a carriage 302 for reciprocating the inkjet head 10 in the main scanning direction which is the axial direction of the platen 300, and an ink tube 30 for the inkjet head 10.
It has an ink tank 301 for supplying the ink via 6. Reference numeral 303 denotes a pump, which is used for cap 3 when an ink ejection failure occurs in the inkjet head 10.
04, it is used to suck ink through the waste ink collection tube 308 and collect it in the waste ink reservoir 305.

FIG. 2 is an exploded perspective view of the ink jet head 10 described above. 3 is a cross-sectional configuration diagram of the entire assembled inkjet head, and FIG. 4 is a view taken along the line AA of FIG.

The ink jet head 10 of this embodiment is of a type that ejects ink droplets by changing the volume of the ink chamber communicating with the nozzle by vibrating the vibrating plate using electrostatic force. Of course, it is also possible to adopt a type in which the volume of the ink chamber communicating with the nozzle is changed using a piezoelectric element or the like to eject ink droplets. Further, in this example, the edge eject type in which the ink droplets are ejected from the nozzle holes provided in the end portion of the substrate is used, but the face eject type in which the ink droplets are ejected from the nozzle holes provided in the upper surface of the substrate may be used.

The structure of the ink jet head 10 will be described with reference to FIGS. The inkjet head 10 of this example has a laminated structure in which three substrates 1, 2, and 3 are stacked. The intermediate substrate 2 is, for example, a silicon substrate, and includes a plurality of nozzle grooves 21 that are formed in parallel on the surface of the substrate 2 from one end at equal intervals so as to form a plurality of nozzle holes 4, and each nozzle groove. 21 and a bottom wall that forms a discharge chamber 6 (ink chamber) whose bottom wall functions as the vibrating plate 5, and an ink inlet port that forms an orifice 7 provided at the rear of the recess 22. And a recess 24 that will form a common ink cavity 8 for supplying ink to each ejection chamber 6.

Further, in the lower portion of the vibrating plate 5, a concave portion 25 which constitutes a vibrating chamber 9 for mounting an electrode described later is formed.
Is provided. The nozzle grooves 21 have a pitch of about 2 mm and a width of about 40 μm. On the other hand, the common electrode 17 is formed on the upper surface of the intermediate substrate. The upper substrate 1 joined to the upper surface of the intermediate substrate 2 is made of, for example, glass or plastic, and the joining of the upper substrate 1 constitutes the nozzle hole 4, the ejection port 6, the orifice 7 and the ink cavity 8. An ink supply port 14 communicating with the ink cavity 8 is formed in the upper substrate 1. The ink supply port 14 is connected to the ink tank 301 (see FIG. 1) via the connection pipe 16 and the tube 306.

Lower substrate 3 bonded to the lower surface of intermediate substrate 2
Is made of, for example, glass or plastic, and the vibrating chamber 9 is constituted by joining the lower substrate 3, and the individual electrodes 31 are formed on the surface of the lower substrate at respective positions corresponding to the respective vibrating plates 5. The individual electrode 31 has a lead portion 32 and a terminal portion 33. Further, except for the terminal portion 33, the electrode 3
The entire 1 and the lead portion 32 are covered with an insulating film 34. A lead wire 35 is bonded to each terminal portion 33.

In the ink jet head 10 constructed by stacking the substrates in this manner, a driver 220 is further connected between the common electrode 17 formed on the intermediate substrate 2 and the terminal portion 33 of each individual electrode 31. The ink 11 is supplied from the ink tank 301 to the inside of the intermediate substrate through the ink supply port 14 and fills the ink cavity 8, the ejection port 6, and the like. The distance between the electrode 31 and the diaphragm 5 is 1 μm.
Is held to a degree. In FIG. 2, 13 is an ink droplet ejected from the nozzle hole 4.

The ink used is prepared by dissolving or dispersing a surfactant such as ethylene glycol and a dye or pigment in a main solvent such as water, alcohol or toluene. Furthermore, if a heater or the like is attached to the inkjet head, hot melt ink can also be used.

When the driver 220 applies, for example, a positive voltage pulse to the individual electrode 31 to charge the surface of the electrode 31 to a positive potential, the lower surface of the corresponding diaphragm 5 is charged to a negative potential. . Therefore, the diaphragm 5 is attracted by the electrostatic force and bends downward. Next, when the voltage pulse applied to the electrode 31 is turned off, the diaphragm 5 returns to its original position. By this returning operation, the internal pressure of the ejection chamber 6 is rapidly increased, and the ink droplets 13 are ejected from the nozzle holes 4 toward the recording paper 105. Then, the vibration plate 5 bends downward, so that the ink 11 is replenished from the ink cavity 8 to the ejection chamber 6 via the orifice 7.

FIG. 5 shows the drive control system of the ink jet head 10 in the control system of the ink jet printer of this embodiment. In the figure, reference numeral 201 denotes a printer control circuit, which can be constituted by, for example, a one-chip microcomputer. This printer control circuit 20
1 includes a RAM 205 and a ROM via internal buses 202, 203 and 204 including an address bus and a data bus.
206 and character generator ROM (CG-
ROM) 207 is connected. A control program is stored in advance in the ROM 206, and a drive control operation of the inkjet head 10 as described below is executed based on the control program called from here and activated. The RAM 205 is used as a working area in drive control. A dot pattern corresponding to an input character is developed in the CG-ROM 207.

Reference numeral 210 is a head drive control circuit, and under the control of the printer control circuit 201, the head driver 22
A drive signal, a clock signal, etc. are output to 0. Further, print data DATA is supplied via the data bus 211.

The head driver 220 is composed of, for example, a TTL array, generates drive voltage pulses corresponding to the input drive signal, and applies these to the individual electrode 31 and the common electrode 17 to be driven. Ink droplets are ejected from the corresponding nozzle holes 14. In order to generate a driving voltage pulse signal, the head driver 2
The ground voltage GND, the drive voltage Vn, and the like are supplied to 20. These voltages are drive voltages Vc of the power supply circuit 230.
It is generated from c.

FIG. 6 shows a flow chart of a schematic operation of the ink jet printer 1 having the above-mentioned configuration.
FIG. 7B shows a nozzle recovery operation subroutine in FIG.
Shows a print operation subroutine.

First, the overall operation will be described. Step S
At T1, the printer mechanism is initialized. Next, in step ST2, a nozzle recovery operation is performed immediately after the power is turned on. This nozzle recovery operation is shown in FIG.
It comprises a series of steps shown in steps ST21 to ST23.

In this nozzle recovery operation, the carriage 302 carrying the ink jet head 10 is moved from the standby position to the position of the cap 304 in step ST21. Next, in step ST22, the nozzle recovery operation, that is, the preliminary ejection drive is performed. Preliminary ejection drive of the nozzles is a diaphragm corresponding to all nozzles in order to eject defective ink that causes defective ejection of ink, such as highly viscous ink in the nozzle hole portion of the inkjet head 10. 5 is driven so that ink droplets are ejected from all nozzles a predetermined number of times. After that, the carriage 302 is returned to the standby position again in step ST23.

Returning to the flowchart of FIG. 6 again, in step ST3, the time from the previous nozzle recovery operation is counted. This count is based on the printer control circuit 2
01 using a built-in counter. When the time interval for performing the nozzle recovery operation has elapsed, the process proceeds from step ST3 to step ST9 and the nozzle recovery operation is performed again. If not, it is determined in step ST4 whether or not to print, and if the printing operation is to be performed,
After resetting the count value of the nozzle recovery operation period in step ST5, the process proceeds to step ST6, and the printing operation for printing characters and the like on the recording paper 105 is executed.

FIG. 7B shows this printing operation. As shown in this figure, first, in step ST61, the count value n is set to "1", and in step ST62, the carriage 302 is moved by one dot in the main scanning direction. In steps ST63 and ST64, the diaphragm 5 of the nozzle corresponding to the designated dot based on the print data DATA is driven to perform the suction and ejection operations of the ink of the nozzle. Next, in step ST65, the count value n is incremented by "1", and in step ST66 it is determined whether or not the count value n is the final dot in the main scanning direction. If it is the final dot, the printing operation is ended. If not, the process returns to step ST62 and the above operation is repeated.

After the printing operation for one line in the main scanning direction is completed in this way, it is determined in step ST10 in FIG. 6 whether or not to continue the process. If it is continued, the process returns to step ST3. If not, the process ends.

Here, in the ink jet printer of this example, during the printing operation shown in FIG. 7B, that is, during the ejection drive for printing for driving the ink jet head when printing characters, symbols, etc. on the recording paper, Ink droplets are ejected by a hitting method. On the other hand, during the preliminary ejection drive for the nozzle recovery operation shown in FIG. 7A, ink droplets are ejected by the push-push method.

FIG. 8A shows a circuit example of a head driver 220 portion attached to each diaphragm 5 in order to drive an ink jet head by such a different driving method. Further, in FIG. 8B, the energizing pulse Pw supplied from the head drive control circuit 210 side.
And the waveform of the drive voltage pulse V applied between the diaphragm 5 (common electrode 17) and the individual electrode 31 by the head driver 220.

In FIG. 8A, the capacitance C represents the capacitance formed between the diaphragm 5 and the individual electrode 31. In this circuit, when the energizing pulse Pw is in the off state, the transistor 51 is held in the off state, whereas the transistor 52 side is held in the on state via the knot circuit 53. As a result, the potential V1 on the individual electrode 31 side is Vn.
Is held at the same level as the potential Vcom on the common electrode 17 side, and the potential difference between the electrodes is zero. In this state, when the energizing pulse Pw rises to ON, the transistor 51
Is turned on, the transistor 52 is turned off, the potential Vcom of the common electrode 17 rises to Vn, and the individual electrode 3
The potential V1 of 1 is set to the ground potential GND. As a result, the potential difference V between the electrodes becomes (Vcom-V1). When the energizing pulse Pw falls, the potential difference V becomes zero again.

As shown in FIG. 8B, in this example, the energizing pulse Pw is the energizing pulse Pw0 (i) (i = 1, 2, 3, ...) With a large pulse width during the preliminary ejection drive. The voltage is applied at a constant timing. Due to the drive voltage pulse V representing the potential difference between the electrodes thus generated, an electrostatic force is generated between the electrodes, the diaphragm 5 is attracted to the individual electrode 31 side, and the volume of the ejection chamber 6 increases.
The pulse width W0 of the energizing pulse Pw0 (i) is set to such a width that ink droplets are ejected by the push-push method.

That is, when the vibrating plate 5 is attracted to the individual electrode 31 side by the electrostatic force generated by the driving voltage pulse V, the ink meniscus in the nozzle hole 4 is discharged.
Is drawn inside as the volume increases. After the diaphragm 5 is displaced to the maximum by the electrostatic force, this state is maintained so that the ink meniscus of the nozzle hole 4 is directed from the retracted position toward the ejection side again as the ink pressure in the ejection chamber fluctuates. The vibration of moving to the drawing side again after repeating the above movement is attenuated, and the vibration is attenuated due to the viscosity of the ink or the like. As a result, the ink meniscus returns to the opening position of the ink nozzle 4 in a substantially static state. At this time, the time when the energizing pulse Pw falls, that is, its pulse width W0 is set so that the diaphragm 5 can be restored to its original state by its own elastic force. Since the pulse width is set in this way, the volume of the discharge chamber 6 is reduced by the vibrating plate 5 that is released from the electrostatic force and returns to its original position, and the ink pressure generated by this reduces the ink liquid from the nozzle hole 4. Droplets are ejected.

On the other hand, in the printing ejection drive for actually printing characters on the recording paper, the energizing pulse P
w1 (i) (i = 1, 2, 3, ...) Is set to a pulse width W1 narrower than the pulse width W0 at the time of the above-described preliminary ejection drive, and the ejection operation of ink droplets by the ejection method is performed. It is supposed to be done. That is, in this case,
When the vibration plate 5 is attracted to the individual electrode 31 side by the electrostatic force generated by the drive voltage pulse V, the volume of the ejection chamber 6 is reduced by this, and the ink meniscus of the nozzle hole 4 is moved to the ejection chamber 4 side. Be drawn in. The pulse width W1 of the energizing pulse Pw1 (i) is set so that the diaphragm 5 can be restored to the original state when the ink meniscus is pulled in to the maximum. By setting in this way, ink droplets are ejected from the nozzle holes 4 by the ink pressure accompanying the increase of the volume of the ejection chamber 4 due to the return of the vibration plate 5 and the kinetic energy at the time of elastic return of the vibration plate itself. Done.

As described above, in the driving method of this embodiment, the pulling-out method is used during the ejection drive for printing for printing characters and the like, and the pushing method is used during the preliminary ejection drive.

Since the pulling-out method also uses the kinetic energy of the vibrating plate at the time of elastic recovery as the ejection energy of the ink droplets, a larger amount of ink droplets can be ejected at a higher speed than the pushing-out method. it can. In this example, since this method is adopted for the usual ink droplet ejection drive for printing characters and the like, high-speed and stable ink droplet dot printing can be realized.

On the other hand, since the push-type method does not substantially utilize the kinetic energy of the vibrating plate, the discharge amount and discharge speed of ink droplets are generally inferior to the pull-type method. However, the ejection characteristics of the ink droplets are not significantly affected by the characteristics of the ink in the ink chamber, in particular, the change in the dynamic characteristics associated with the change in the viscosity thereof. That is, unlike the hitting method, the ejection characteristics of the ink droplets do not deteriorate due to changes in the dynamic characteristics that accompany changes in the viscosity of the ink. In this example, this method is adopted for the preliminary ejection drive in which the ejection operation of the ink droplets is performed in the state where the ink viscosity is increased. Therefore, appropriate ink droplets can always be ejected without being affected by fluctuations in ink viscosity, and the nozzle can be reliably returned to the recovery state.

(Other Embodiments) FIG. 9 (a) shows FIG.
Another example of the drive circuit of each diaphragm 5 shown in (a) is shown. In this circuit configuration, the head drive control circuit 21
The polarity inversion pulse Pr generated on the side of 0 is supplied to the transistor 54 and is also supplied to the transistor 55 via the knot circuit 56. The potential Vcom on the side of the common electrode 17 is controlled by this pulse Pr, and during the preliminary ejection drive, a drive voltage having a polarity opposite to that of the normal ejection drive for printing is applied between the electrodes, so that the residual charge between the electrodes is reduced. To remove.

When the polarity inversion pulse Pr is off, the transistor 54 is off and the transistor 55 is on, so that the potential Vcom side of the common electrode 17 is held at Vn. On the contrary, when the pulse Pr rises to ON, the transistor 54 is switched to ON, so that the potential V of the common electrode is
com is held at the ground potential.

As shown in FIG. 9B, the off-state pulse width W2 between the energizing pulses Pw2 (i) supplied during the preliminary ejection is the pulse width of the pulse Pw0 (i) in FIG. 8B. It is set similarly to W0. Therefore, the ejection operation of the ink droplets is performed by the push-push method.
Further, during the pre-ejection drive, the polarity reversal pulse Pr is held in the ON state, so the common electrode potential Vcom is held at the ground potential.

On the other hand, during the printing discharge drive for printing characters and the like, the on-state pulse width W3 of the through pulse Pw3 (i) is the pulse Pw1 in FIG. 8 (b).
It is set similarly to the pulse width W1 of (i). Therefore, the ejection operation of the ink droplets is performed by the hitting method. Further, during the ejection drive for printing, the polarity reversal pulse Pr is held in the OFF state, so that the common electrode potential Vc
om is held at Vn. As a result, the polarity of the drive voltage pulse V applied between the electrodes is switched to the polarity opposite to that in the above-described preliminary ejection drive.

As described above, also in the driving method of this embodiment, the ink droplets are ejected by the push ejection method during the preliminary ejection drive, and the ink droplets are ejected by the pull ejection method during the ejection drive during printing. Therefore, as in the case shown in FIG. 8, an appropriate preliminary ejection operation can always be performed even when the ink characteristics have changed, and during normal printing, ejection of ink droplets with a stable liquid volume can be performed at high speed. The advantage is that it can be done.

Further, in this example, the polarity of the drive voltage pulse applied between the electrodes during the preliminary ejection driving is set to be opposite to the polarity during the normal printing ejection driving. Therefore, since the residual charge generated between the electrodes can be removed during the preliminary ejection drive, there is also an advantage that printing defects and the like due to the residual charge can be avoided.

The above description is for the case where the driving method of the present invention is applied to an ink jet head which discharges ink droplets by utilizing electrostatic force. However, the driving method of the present invention is also applicable to an inkjet head of a system that ejects ink droplets by changing the volume of the ink chamber (the ejection chamber 6 in the above example) using an electromechanical conversion element such as a piezoelectric element. It can be applied similarly.

[0053]

As described above, according to the present invention, in the ink jet head of the type that ejects ink droplets by changing the volume of the ink chamber, the preliminary ejection drive for nozzle recovery is performed by the push-push method. I am trying. Therefore, the pre-ejection drive is performed by the hitting method.
Unlike Nau, variations in ink characteristics, particularly avoiding the ejection failure of ink droplets at the time of the preliminary-ejection driving due to an increase in the ink viscosity, it is possible to reliably restore the ink nozzles to a proper state.

Further, in the driving method of the present invention, the preliminary ejection drive is performed by the pulling ejection method, and at the time of the normal printing ejection drive, the pulling ejection method is performed. Well
The inkjet printer of the present invention implements the above method.
It is equipped with driving means for carrying out. Therefore, according the present invention, both to be able to reliably recover the ink nozzle by the preliminary-ejection driving, at the time of printing, such as an ordinary character, can be performed ejection operation stable ink droplets at high speed.

Further, according to the driving method of the present invention, the above-mentioned driving method is adopted in the ink jet head of the type in which the volume of the ink chamber is changed by utilizing the electrostatic force to eject the ink droplets, and the preliminary ejection driving is performed. At times, ink droplets are ejected by applying a voltage pulse having a polarity opposite to that of a drive voltage pulse applied between electrodes during normal printing ejection drive. Therefore, it is possible to remove the residual charges generated between the electrodes during the preliminary ejection drive.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an overall configuration of an inkjet printer to which the present invention has been applied.

2 is an exploded perspective view showing an inkjet head mounted in the printer of FIG. 1. FIG.

FIG. 3 is a schematic cross-sectional view showing the inkjet head of FIG.

FIG. 4 is a view taken along the line AA of FIG.

5 is a schematic block diagram showing a control system of an inkjet head in the inkjet printer of FIG.

FIG. 6 is a schematic flowchart showing an operation of the inkjet printer of FIG.

FIG. 7A is a flowchart showing a subroutine of a nozzle recovery operation, and FIG. 7B is a flowchart showing a dot printing operation for one main scanning line.

FIG. 8A is a schematic circuit diagram showing a circuit configuration example of a head driver, and FIG. 8B is a timing chart showing the operation of each part of the circuit.

FIG. 9A is a schematic circuit diagram showing another example of the circuit configuration of the head driver, and FIG. 9B is a timing chart showing the operation of each part of the circuit.

[Explanation of symbols]

1, 2, 3 substrates 4 nozzle holes 5 diaphragm 6 Discharge chamber (ink chamber) 10 inkjet head 13 ink droplets 17 Common electrode 31 individual electrodes 201 Printer control circuit 210 Head drive control circuit 220 head driver V1 Individual electrode potential Vcom Common electrode potential Pw energizing pulse

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Maruyama 3-3-5 Yamato, Suwa City, Nagano Seiko Epson Corporation (56) Reference JP-A-6-198874 (JP, A) JP-A 7-214769 (JP, A) JP-A-3-224745 (JP, A) JP-B 6-39163 (JP, B2) (58) Fields investigated (Int.Cl. ⁷ , DB name) B41J 2/045 B41J 2/055 B41J 2/18 B41J 2/185

Claims (6)

(57) [Claims] 1. A nozzle and ink communicating with the nozzle.
Chamber, a displacement plate provided in a part of the ink chamber,
Displace the displacement plate to change the volume of the ink chamber.
Ink droplets are ejected from the nozzle by
Ink jet for printing characters etc.
In the driving method of the head, Only when pre-driving is performed to recover the nozzle.
Each of the ink droplets is ejected by the displacement plate of the ink chamber.
Displace in the direction in which the volume increases, and
The ink meniscus of the moving nozzle is pulled in once
After being entrapped, it remains substantially stationary at the opening position of the nozzle.
At the time of restoration, the displacement plate is reduced in volume of the ink chamber.
By displacing it in the direction ofI This should be done when driving to eject ink droplets for printing characters, etc.
Each of the ink droplets is ejected by the displacement plate of the ink chamber.
Displace in the direction of increasing volume, and increase the volume.
And the ink meniscus of the nozzle is essentially the most retracted
The volume of the ink chamber is reduced when the displacement plate
By moving it in the direction Characterized by
Inkjet head driving method. 2. The displacement plate according to claim 1 , wherein the displacement plate is a vibration plate provided in a part of the ink chamber, an electrode is provided facing the vibration plate, and the electrode is provided between the electrode and the vibration plate. A method for driving an inkjet head, characterized in that by applying a drive voltage pulse, the vibration plate is deformed using electrostatic force to eject ink droplets from the nozzles. 3. The ejection drive for printing according to claim 2 , wherein the drive voltage pulse having a first polarity is applied between the diaphragm and the electrode, and the preparatory ejection drive includes the vibration plate. And a driving pulse voltage having a second polarity opposite to the first polarity is applied between the electrode and the electrode. 4. A nozzle, an ink chamber communicating with the nozzle, a displacement plate provided in a part of the ink chamber, and the displacement plate displaced in a direction in which the volume of the ink chamber increases.
As the ink volume of the nozzle increases.
When the scrap is substantially pulled in most, the displacement plate is
The ink in the direction in which the volume of the ink chamber decreases.
By means of which each ink droplet is ejected, and the ejection ejection means for printing that prints characters and the like by the ejected ink droplet, and the ejection of each ink droplet at the time of pre-ejection drive for recovering the nozzle, The displacement plate is displaced in a direction in which the volume of the ink chamber increases, and after the ink meniscus of the nozzle that moves with the increase in the volume is temporarily drawn, the displacement plate returns to the opening position of the nozzle in a substantially stationary state. And a preliminary ejection drive means for displacing the displacement plate in a direction in which the volume of the ink chamber decreases at that time. 5. The displacement plate according to claim 4 , wherein the displacement plate is a vibration plate provided in a part of the ink chamber, an electrode is provided facing the vibration plate, and the electrode is provided between the electrode and the vibration plate. An ink jet printer characterized in that by applying a drive voltage pulse, the vibration plate is deformed using electrostatic force to eject ink droplets from the nozzles. 6. The ejection driving device for printing according to claim 5 , wherein the driving voltage pulse of the first polarity is applied between the diaphragm and the electrode, and the preliminary ejection driving device includes the diaphragm. An inkjet printer, wherein the drive pulse voltage having a second polarity opposite to the first polarity is applied between the electrode and the electrode.