JP3613297B2 - Inkjet recording device - Google Patents

Description

[0001]
[Field of the Invention]
The present invention relates to a technique for preventing clogging of nozzle openings of a recording apparatus using an on-demand type ink jet recording head.
[0002]
[Prior art]
The on-demand type ink jet recording head includes a plurality of nozzle openings and a pressure generation chamber communicating with each nozzle opening, and is configured to generate ink droplets by expanding and contracting the pressure generation chamber in response to a print signal. Has been. In such a recording head, since new ink is sequentially supplied to the nozzle openings where the printing operation is performed, there is almost no risk of clogging. Clogging is likely to occur when it is extremely low or in a resting state.
[0003]
For this reason, when the printing operation is continued for a certain period of time, the recording head is retracted to the capping means in the non-printing area, where a drive signal is applied to the piezoelectric vibrator to drop ink droplets from all nozzle openings toward the cap. It has been proposed to perform a so-called flushing operation for forcibly ejecting water.
[0004]
[Problems to be solved by the invention]
However, if such measures are taken, the printing operation is interrupted, resulting in a decrease in printing speed and consumption of ink. Therefore, the pressure generation chamber connected to the nozzle opening that does not generate ink droplets during the printing operation is provided. Many techniques have been proposed to prevent clogging by applying a minute drive signal that does not cause ink droplets to be ejected to a piezoelectric vibrator and causing the meniscus in the vicinity of the nozzle opening to vibrate minutely (Japanese Patent Laid-Open No. 55-123476). JP, 57-61576, U.S. Pat. No. 4,350,989).
[0005]
According to these, the number of flushing operations can be reduced to prevent a decrease in printing speed and ink consumption, but an audible sound caused by minute vibration becomes noise and the number of vibrations of the piezoelectric vibrator increases dramatically. Therefore, there is a problem of shortening the life of the recording head.
The present invention has been made in view of such problems, and an object of the present invention is to perform ink jet recording capable of reliably preventing clogging of nozzle openings while reducing the number of vibrations of the piezoelectric vibrator. Is to provide a device.
[0006]
[Means for Solving the Problems]
In order to solve such a problem, an ink jet recording head having a pressure generating chamber formed by a nozzle plate having a nozzle opening and a vibration plate deformed by displacement of the piezoelectric vibrator, and the nozzle opening A drive signal generating means for generating a first drive signal for ejecting ink droplets from the nozzle, a second drive signal for vibrating the meniscus to such an extent that no ink droplets are ejected from the nozzle openings, and the recording head in a non-printing state. If the second drive signal is Ink droplet ejection A first mode applied to the piezoelectric vibrator with a period longer than the period, and a time longer than the application time in the first mode immediately before printing when the recording head switches from a non-printing state to a printing state. Means for selecting a second mode in which the second drive signal is continuously applied to the piezoelectric vibrator.
[0007]
[Action]
In the resting state, the meniscus is minutely vibrated at a minimum necessary period to reduce the fatigue of the piezoelectric vibrator and prevent clogging. Immediately before the start of printing, the minute vibration is continuously performed to reliably eliminate clogging of the nozzle openings, and the printing operation is started after the ink in the vicinity of the nozzle openings is replaced with the ink in the pressure generating chamber.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Therefore, details of the present invention will be described below based on the illustrated embodiment.
FIG. 1 shows a structure around a printing mechanism of a printer of the present invention. In FIG. 1, reference numeral 1 denotes a carriage, which is connected to a pulse motor 3 via a timing belt 2 and guided to a guide member 4. Thus, the recording paper 5 is configured to reciprocate in the paper width direction.
[0009]
An ink jet recording head 6 to be described later is attached to the carriage 1 on the surface facing the recording paper 5, in this embodiment on the lower surface. The ink jet recording head 6 receives ink replenishment from the ink cartridge 7 mounted on the upper portion of the carriage 1 and ejects ink droplets onto the recording paper 5 in accordance with the movement of the carriage 1 to form dots. Print images and text on recording paper.
[0010]
8 is a capping device that is provided in a non-printing area and seals the nozzle openings of the recording head 6 during a pause while receiving ink droplets from the recording head 6 by a flushing operation performed during the printing operation. It is. In the figure, reference numeral 9 denotes a cleaning means.
[0011]
FIG. 2 shows an embodiment of the recording head 6. In the figure, reference numeral 10 denotes a first cover plate, which is composed of a thin zirconia plate having a thickness of about 10 μm, and pressure generation described later is formed on the surface thereof. A drive electrode 12 is formed to face the chamber 11. A piezoelectric diaphragm 13 made of PZT or the like is formed on the surface of the drive electrode 12.
[0012]
The pressure generation chamber 11 contracts and expands in response to the flexural vibration of the piezoelectric vibration plate 13, ejects ink droplets from the nozzle openings 14, and sucks ink in the common ink chamber 16 through the ink supply port 15.
[0013]
Reference numeral 17 denotes a spacer having a thickness suitable for forming the pressure generating chamber 11, for example, a 150 μm zirconia (ZrO 2) ceramic plate made of a through hole, and a second lid described later. Both surfaces are sealed by the body 18 and the first lid body 10 to form the pressure generation chamber 4 described above.
[0014]
Reference numeral 18 denotes a second lid, which is also connected to a later-described ink supply port 15 and a pressure generating chamber 11 on a ceramic plate such as zirconia, and the ink in the pressure generating chamber 11 is directed toward the nozzle opening 14. An ink discharge port 20 for discharging is formed, and is fixed to the other surface of the spacer 17.
[0015]
Each of the members 10, 17, and 18 is formed in the actuator unit 21 without using an adhesive by forming a clay-like ceramic material into a predetermined shape, laminating and firing the materials.
[0016]
Reference numeral 22 denotes an ink supply port forming substrate, which is made of a metal such as non-rust steel or ceramics having ink resistance so that it can serve as a fixed substrate for the actuator unit 21 and can also be connected to an ink cartridge. Has been.
[0017]
The ink supply port forming substrate 22 is provided with an ink supply port 15 for connecting a common ink chamber 16 (described later) and the pressure generation chamber 11 at one end of the pressure generation chamber 11 side. A communication hole 23 that connects the nozzle opening 14 and the ink discharge port 20 of the actuator unit 21 is provided on the end side.
[0018]
Reference numeral 24 denotes a common ink chamber forming substrate, and a plate material having a thickness suitable for forming the common ink chamber 16, for example, a plate material having corrosion resistance such as 150 μm stainless steel, corresponding to the shape of the common ink chamber 16. A communication hole 26 that connects the hole and the nozzle opening 14 of the nozzle plate 25 and the ink discharge port 20 is formed.
[0019]
The ink supply port forming substrate 22, the common ink chamber forming substrate 24, and the nozzle plate 25 are grouped together in the flow path unit 27 by adhesive layers S and S made of a heat welding film, an adhesive, or the like. .
[0020]
A recording head is configured by fixing the actuator unit 1 with an adhesive on the surface of the ink supply port forming substrate 22 of the flow path unit 27.
[0021]
With such a configuration, when the piezoelectric vibrator 13 is charged and the piezoelectric vibrator 13 bends, the pressure generating chamber 11 contracts. As a result, the ink in the pressure generating chamber 11 is pressurized and ejected as ink droplets from the nozzle openings 14 to form dots on the recording paper.
[0022]
When the electric charge of the piezoelectric vibrator 13 is discharged after a predetermined time has elapsed, the piezoelectric vibrator 13 returns to the original state. As a result, the pressure generating chamber 11 expands, the ink in the common ink chamber 16 flows into the pressure generating chamber 11 via the ink supply port 15, and ink for the next printing is supplied to the pressure generating chamber 11. The
[0023]
On the other hand, when the piezoelectric vibrator 13 is charged with a minute voltage that does not cause the ink drops to be ejected to the piezoelectric vibrator 13 and the piezoelectric vibrator 13 is deflected by a small amount, the pressure generating chamber 11 is also slightly contracted. Thereby, a minute amount of meniscus in the vicinity of the nozzle opening 14 is pushed out to the nozzle opening 14 side.
[0024]
Next, when the electric charge of the piezoelectric vibrator 13 is discharged to return to the original state, the pressure generation chamber 11 expands by a small amount, and the meniscus pushed out to the nozzle opening side is pulled back to the pressure generation chamber 11 side.
[0025]
Thus, when the piezoelectric vibrator 13 is deflected by a minute amount at the same cycle as the printing timing or returned to the original state, the meniscus in the vicinity of the nozzle opening also vibrates by a minute amount, and the ink near the nozzle opening is pressurized. The ink in the generation chamber 11 is replaced to help prevent clogging.
[0026]
FIG. 3 shows an embodiment of a control device for driving the recording head 6 described above. In FIG. 3, reference numeral 30 denotes a control means, which receives a print command signal and print data from the host and generates a drive signal which will be described later. The circuit 31, the head drive circuit 32, and the carriage drive circuit 33 are controlled to execute a printing operation, and flushing is performed at the capping position or the above-described meniscus is minutely vibrated by time data of a print timer 36 described later. For this purpose, the magnitude, application period, and time of the second and third drive signals are controlled.
[0027]
The drive signal generation circuit 31 is configured to generate a trapezoidal first drive signal (FIG. 4 (a)) having a voltage value VH necessary for ejecting ink droplets from the nozzle openings 11.
The first drive signal has a duration T1 of the natural vibration period Tc of the pressure generation chamber 13, that is,
When the inertance of the nozzle opening 11 is Ln, the inertance of the ink supply port is Li, the compliance of the diaphragm is Cv, and the compliance of the ink is Cink,
Tc = 2π√ [(CV + Cink) × Ln × Li] / (Ln + Li)
Is set to match the value represented by.
As a result, the displacement of the piezoelectric vibrator 13 can be effectively converted into the movement of the meniscus.
[0028]
The drive circuit 32 selectively applies the first drive signal (FIG. 4A) of the drive signal generation circuit 31 to the piezoelectric vibrator 13 corresponding to the print data, and in the standby state, the first drive signal The second drive signal (FIG. 4 (b)) of about ½ is applied to the first drive regardless of the presence or absence of ink ejection for printing (ink ejection by the first drive signal) during the printing period. A third drive signal (FIG. 4C) about 1/5 of the signal is applied.
[0029]
That is, the piezoelectric vibrator 13 in which the recording head is present in the print area and the print data is present is supplied with the third drive signal (FIG. 4C) and the first drive signal (FIG. 4C) before ink droplet ejection. 4 (A)) is applied as a pair, and only the third drive signal (FIG. 4 (C)) is applied to the piezoelectric vibrator 13 in which the recording head 6 exists in the print region and no print data exists. To do.
[0030]
Reference numeral 35 denotes a second drive signal corresponding to the voltage values of the second and third drive signals, data for adjusting the gradient of the second drive signal corresponding to the temperature, and the amount of ink consumed during printing. Data for adjusting the signal level is stored. Reference numeral 36 denotes a print timer for measuring the duration of the printing operation, which is activated when the printing operation starts and is reset by the flushing operation.
[0031]
A print amount counter 37 counts the number of dots printed at the time of printing and detects the ink consumption amount. In the figure, reference numeral 38 denotes temperature detecting means for detecting the temperature around the recording head.
[0032]
FIG. 5 shows an embodiment of the drive signal generation circuit 31 described above. In FIG. 5, reference numeral 40 denotes a one-shot multivibrator that converts a timing signal from an external device into a pulse signal having a constant width, and is synchronized with the timing signal. Then, a positive signal and a negative signal are output from the output terminal. One terminal is connected to the base of an NPN transistor 41, to which a PNP transistor 42 is connected. When a timing signal is input, the capacitor 53 is connected at a constant current Ir until the power supply voltage VH is reached. Charge.
[0033]
An NPN transistor 48 is connected to the other terminal of the one-shot multivibrator 40. When the timing signal is switched, the transistor 42 is turned off, while the transistor 48 is turned on to charge the capacitor 43. It is discharged at a constant current If until the charged electric charge drops to substantially zero voltage.
[0034]
That is, assuming that the base-emitter voltage of the transistor 44 is VBE44 and the resistance value of the resistor 46 is Rr, the charging current Ir is
Ir = Vbe44 / Rr
If the capacitance of the capacitor 43 is C0, the charging voltage rise time Tr is
Tr≈C0 × VH / Ir
It becomes.
[0035]
On the other hand, the discharge current If of the drive signal is represented by VBE45 as the base-emitter voltage of the transistor 45 and Rf as the resistance value of the resistor 47.
If = Vbe45 / Rr
And the fall time is
Tf≈C0 × VH / If
It becomes.
[0036]
As a result, the terminal voltage of the capacitor 43 has a region that rises at a constant gradient α, a saturation region that holds a constant value, and a region that falls at a constant gradient β, as shown in FIG. A trapezoidal waveform is obtained, and the current is amplified by the transistors 49 and 50. The piezoelectric vibrators 13, 13, 13... To drive It is output as a motion signal.
[0037]
Next, the operation of the drive signal generation circuit 31 described above will be described.
All the switching transistors T, T, T... Are turned on for a short time by a signal from the drive circuit 32 described later. As a result, all the piezoelectric vibrators 13, 13, 13 are charged by the voltage from the drive signal generation circuit 31, but the switching signal T, T, T,. Thus, charging is completed at a voltage determined by the time up to this point.
[0038]
For this reason, by controlling the charging time, the second drive signal VH / 2 and the third drive signal Vh / 5 that are suitable for generating minute vibrations during the printing pause or during the printing period can be generated. It becomes possible.
[0039]
As a result, the piezoelectric vibrator 13 has the same gradient α as that during printing as shown in FIGS. 4B and 4C, and 1/2 or 1/1 of the drive signal VH for ink droplet ejection. A flexural vibration that does not allow ink droplets to fly from the nozzle opening 14 with a small voltage of about 5 is caused, and the pressure generating chamber 11 is minutely expanded and contracted to give a minute vibration to the meniscus in the vicinity of the nozzle opening 14.
[0040]
Since the period T1 is the same as the first drive signal for ejecting the ink droplets, it coincides with the natural vibration period of the pressure generation chamber 11, and clogging is prevented with as little displacement as possible. The meniscus can be efficiently microvibrated with a possible amplitude.
[0041]
On the other hand, when a print signal is input from the control means 30, the transistors 42 and 48 are turned on and off to output a trapezoidal voltage, that is, a first drive signal. Since the switching transistors T, T, T,... Connected to the piezoelectric vibrator 13 to be printed are turned on by a drive circuit 32 described later, the switching transistors T, T, T,. become.
[0042]
As a result, the drive signal generated by the drive signal raw circuit 31 flows into the piezoelectric vibrator 13 and charges the piezoelectric vibrator 13 with a constant current. As a result, the piezoelectric vibrators 13, 13,... That should eject ink droplets for printing bend toward the pressure generating chamber 11 side to contract the pressure generating chamber 11 and eject ink droplets from the nozzle openings 14.
[0043]
When a certain period of time elapses, the transistor 48 is turned on and the capacitor 43 is discharged. Accordingly, the piezoelectric vibrators 13, 13, 13... Are discharged to return to the original state, and the pressure generating chamber 11 And the ink in the common ink chamber 16 flows into the pressure generating chamber 11.
[0044]
Hereinafter, the piezoelectric vibrator 1 belonging to the nozzle opening in which dots are to be formed in accordance with the timing signal is subjected to the application of a third drive signal capable of inducing micro-vibration before ink droplet ejection, and then the ink droplet Since only the third drive signal is applied to the piezoelectric vibrator 13 that receives the first drive signal that can generate the dot and does not form dots, the meniscus of all the nozzle openings 14 is Form ink droplets period (Hereinafter referred to as “ink droplet ejection cycle”) Microvibrates in accordance with.
[0045]
When the recording head moves to the non-printing area, a second drive signal that is about ½ of the first drive signal is applied to the piezoelectric vibrator 13 and is charged / discharged by this voltage. Microvibration is performed with a driving force larger than that in the region.
[0046]
The operation of the apparatus configured as described above will be described based on the timing charts of FIGS.
In the resting state and the recording head 6 is not sealed with the capping device 8, the control means 30 reads data defining minute vibrations during the resting period from the data storage means 35, Ink droplet ejection A cycle in which a minute vibration is performed for a predetermined period ΔT, for example, 75 milliseconds, and a minute vibration is stopped for 680 milliseconds, with a time T of a plurality of periods, for example, 755 milliseconds as one period. Repeat during the rest period.
[0047]
In this way, the meniscus is continuously microvibrated for a predetermined time continuously at a period shorter than the time at which the nozzle opening 14 is clogged, whereby the alternating current between the ink in the vicinity of the nozzle opening and the ink in the pressure generating chamber 11 is changed. Prompt and reduce the viscosity of the ink near the nozzle opening to prevent clogging.
[0048]
The temperature rises due to Joule heat by stopping the minute vibration for a time approximately nine times the time ΔT when the minute vibration is performed, that is, for a time shorter than the time when the nozzle opening is clogged after the minute vibration. The piezoelectric vibrator 13 is promoted to be cooled, and fatigue of the piezoelectric vibrator 13 due to continuous micro vibrations is reduced as much as possible.
[0049]
When the carriage 1 starts moving in response to the input of a print signal in a state of waiting by such intermittent micro vibrations, the control unit 30 stops the intermittent micro vibrations at a constant period T. Then, while accelerating the carriage 1 toward the printable speed, the minute vibration is continuously executed again for a time longer than the pause period, for example, 75 milliseconds or more immediately before reaching the printing speed. As a result, the ink in the vicinity of the nozzle opening is replaced with the ink in the pressure generating chamber 11 that has not increased in viscosity, and can be reliably discharged during printing.
[0050]
The output of the second drive signal is stopped immediately before the printing operation is performed in this manner, for example, 100 milliseconds before the print signal is input, and the drive signal generation circuit 31 is a signal of a level necessary for ejecting the ink droplets. System to be able to output.
When the carriage 1 reaches the printing speed and print data is input, the print timer 36 is started. Ru . In this state, the third drive signal is applied to all the piezoelectric vibrators 13 to slightly vibrate the meniscus of the nozzle openings 14. That is, since the third drive signal is as low as VH / 5 compared to the first drive signal for ejecting ink droplets, the ink droplets are ejected even when the piezoelectric vibrator 13 undergoes flexural vibration. However, the meniscus in the vicinity of the nozzle opening 14 is slightly vibrated.
[0051]
Thus, the recording head 6 which is in a standby state in the printing area for printing is Ink droplet ejection The piezoelectric vibrator 13 is driven with a voltage about 1/5 of the first drive signal for ink droplet ejection in accordance with the cycle (FIG. 7 (III)), and clogging of the nozzle opening 14 is prevented. .
[0052]
When a print signal is input in this state, the piezoelectric vibrator 13 to be printed following the third drive signal is moved to the first drive signal while the recording head 6 is scanned in the width direction of the recording paper 5 by the carriage 1. The pressure generation chamber 13 is contracted by increasing voltage, and ink droplets are ejected from the nozzle openings 14. Then, when the predetermined time has elapsed, the piezoelectric vibrator 13 is returned to the original state by the voltage drop of the first drive signal, the pressure generating chamber 13 is expanded, and the ink in the common ink chamber 16 is transferred to the pressure generating chamber 11. Let it flow.
[0053]
The application of the first drive signal stops and the next Ink droplet ejection When the period arrives, the third drive signal is applied to all the piezoelectric vibrators 13 as described above to prevent clogging of the nozzle openings 14 that did not eject ink droplets.
[0054]
When the time of the print timer 36 reaches a predetermined time, for example 10 seconds, during printing, the control means 30 moves the recording head 6 to the flushing position, that is, the position facing the capping device 8, and reaches a predetermined number, for example, several thousand dots. A regular flushing operation for discharging the ink droplets is performed. When the flushing operation is completed, the print timer 36 is reset to perform the time measuring operation again, and the printing operation is started again by the above-described steps.
[0055]
Thereafter, a regular flushing operation is performed every time the print timer 36 measures a predetermined time, and ink is forcibly discharged from all the nozzle openings 14 to prevent clogging.
[0056]
In the above-described embodiment, the level of the second drive signal applied to the piezoelectric vibrator 13 is maintained at a constant value VH / 2 in order to cause the meniscus to vibrate minutely during the pause period in the non-printing region. Based on the data from the printing amount counter 37, the recording head 6 detects the amount of ink ejected by the printing region and by regular flushing. If the amount of ejected ink is large, the voltage value of the second drive signal is lowered. In addition, if the number is small, the voltage value is increased within a range where ink droplets are not ejected, and the minute vibration is performed while taking into consideration the viscosity of the ink in the pressure generating chamber 11, and the piezoelectric vibrator 13 during the resting period. Clogging can be surely prevented while reducing the burden of.
[0057]
The setting of the level of the second drive signal corresponding to the ejection amount of the ink droplets during these printing periods is performed by storing the relationship between the ejection amount and the voltage value in the storage unit 35 in advance, and the ejection amount data of the printing amount counter 37. This can be easily realized by reading the voltage value corresponding to.
[0058]
Further, since the viscosity of ink greatly changes depending on the temperature, when a low voltage signal is applied to the piezoelectric vibrator 13 to cause the meniscus to perform minute vibration, the amplitude value of the minute vibration is greatly changed by temperature. .
[0059]
In order to solve such a problem, it may be possible to adjust the voltage level. However, since the charging time needs to be controlled, the circuit configuration becomes complicated. Therefore, the voltage value of the second drive signal is maintained constant (VH / 2), and only the rising slope and the falling slope are adjusted to correspond to the environmental temperature.
[0060]
That is, the rising slope α is 4 V / μsec for room temperature (25 ° C), the falling slope β is 6.7 V / μsec, and the rising slope α1 is 5 V for a low temperature of 10 ° C. / Μsec, the falling gradient β1 is 8.4 V / μsec, the rising gradient α2 is 3 V / μsec and the falling gradient β2 is 5 V / μsec for high temperatures, and the deflection rate of the piezoelectric vibrator 17 is In addition, the return speed was increased as the temperature decreased to help the movement of the ink whose viscosity increased at low temperatures.
[0061]
The rising slopes α, α1, α2 and the falling slopes β, β1, β2 at these temperatures are adjusted in advance in the storage means 35 in relation to the temperature and the gradients α, α1, α2, β, β1, β2. Can be stored easily and read out by the temperature signal from the temperature detecting means 38.
[0062]
In the above-described embodiment, the third drive signal is set to a constant value of about 20% of the drive signal based on room temperature, for example, 25 ° C., but for ink having a large viscosity change due to temperature, If the temperature is adjusted to about 10% of the drive signal at a low temperature of about 10 ° C. and adjusted to about 30% of the drive signal at a high temperature of about 40 ° C., the meniscus can be vibrated sufficiently in response to a change in temperature. .
[0063]
Furthermore, as shown in FIG. 9, the nozzle opening row B for discharging black ink, the nozzle opening row C for discharging cyan ink, the nozzle opening row M for discharging magenta ink, and the nozzle opening row Y for discharging yellow ink are referred to. For the recording heads 60 and 61 having nozzle opening rows that are driven independently as described above, a plurality of nozzle opening rows B, C, M, and Y, including a first set 62 and a second set 63, are provided. It is desirable to set a time difference ΔT1 between each pair 62 and 63 as shown in FIG. 10 for the second drive signal applied during the rest period.
[0064]
According to this embodiment, the level of audible sound caused by minute vibrations can be reduced to a fraction of the number of sets, and the noise of the recording apparatus can be reduced. In the above-described embodiment, the release of the pause state is detected by the movement of the carriage. However, the same effect can be obtained by detecting the input of the print signal from the external device.
[0065]
FIG. 10 shows an embodiment of a recording head using a piezoelectric vibrator in a longitudinal vibration mode to which the present invention is applicable. In the figure, reference numeral 71 denotes a diaphragm, which corresponds to the tip of the piezoelectric vibrator 72. The flow path unit 75 is formed by a thin plate that is elastically deformed in contact with the nozzle plate 74 with the flow path forming plate 73 interposed therebetween.
[0066]
Reference numeral 76 denotes a base, which includes an accommodation chamber 77 that accommodates the piezoelectric vibrator 72 so as to vibrate, and an opening 78 that supports the flow path unit 75, and the tip of the piezoelectric vibrator 72 contacts the island portion 71 a of the diaphragm 71. The flow path unit 75 is fixed so as to be in contact with each other to constitute a recording head.
[0067]
With such a configuration, when the piezoelectric vibrator 72 is charged and contracts, the pressure generating chamber 83 expands. As a result, the ink in the common ink chambers 80 and 80 flows into the pressure generating chamber 83 via the ink supply ports 81 and 81.
[0068]
When the electric charge of the piezoelectric vibrator 72 is discharged after a predetermined time elapses and the piezoelectric vibrator 72 returns to the original state, the pressure generating chamber 83 contracts and the ink in the pressure generating chamber 83 is compressed and the ink from the nozzle opening 82 is compressed. It is ejected as droplets to form dots on the recording paper.
[0069]
When a small pulse that does not cause ink droplets to be ejected to the piezoelectric vibrator 72 is applied and the piezoelectric vibrator 72 is contracted by a small amount, the pressure generating chamber 83 also expands slightly, so that the meniscus near the nozzle opening 82 generates pressure. It is drawn into the chamber 83 side. Next, when the piezoelectric vibrator 72 is returned to the original state, the pressure generating chamber 83 contracts and the meniscus is pushed back slightly toward the nozzle opening 82 side.
[0070]
As described above, when the piezoelectric vibrator 72 is expanded and contracted by a minute amount at the same cycle as the printing timing, the meniscus in the vicinity of the nozzle opening 82 also vibrates by a minute amount. It is possible to prevent clogging of the nozzle openings by replacing with 83 ink.
[0071]
In the above-described embodiment, the printing operation of the recording head is such that the first drive signal is applied after the third drive signal is applied, but the first drive signal is applied. Thereafter, the same effect is obtained even when a third drive signal is applied.
[0072]
【The invention's effect】
As described above, the present invention According to In the rest state, the vibration of the piezoelectric vibrator is reduced by reducing the number of vibrations of the piezoelectric vibrator as much as possible by making the meniscus minutely vibrate for a certain period of time shorter than the time when the nozzle opening is not clogged. At the same time, clogging is prevented, and minute vibration is continuously performed immediately before the start of printing. Teno The printing operation can be ensured by replacing the ink in the vicinity of the nozzle opening with the ink in the pressure generating chamber having a low viscosity.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of an ink jet recording apparatus to which the present invention is applied.
FIG. 2 is a cross-sectional view showing an embodiment of an ink jet recording head.
FIG. 3 is a block diagram of an apparatus showing an embodiment of the present invention.
FIGS. 4A to 4C are waveform diagrams showing first, second, and third drive signals applied to the piezoelectric vibrator, respectively.
FIG. 5 is a diagram illustrating an example of a drive signal generation circuit.
FIGS. 6A and 6B are diagrams showing drive signals applied to the piezoelectric vibrators during a pause period, corresponding to the movement of the carriage. FIGS.
FIGS. 7A to 7I are waveform diagrams showing drive signals applied to a piezoelectric vibrator for ink ejection and non-ink ejection during a printing period, respectively.
FIG. 8 is a diagram showing an embodiment of an ink jet recording head to which the present invention can be applied, in the form of an array of nozzle openings.
FIGS. 9 (I) to (III) are diagrams showing other embodiments of the present invention in the form of application of the second drive signal applied during the idle period, respectively.
FIG. 10 is a diagram showing an embodiment of a recording head of another type to which the present invention can be applied.
[Explanation of symbols]
6 Inkjet recording head
8 Capping device
9 Cleaning device
11 Pressure generation chamber
13 Piezoelectric vibrator
14 Nozzle opening

Claims (8)

An ink jet recording head having a pressure generating chamber formed by a nozzle plate having a nozzle opening and a diaphragm deformed by displacement of the piezoelectric vibrator;
Drive signal generating means for generating a first drive signal for ejecting ink droplets from the nozzle openings and a second drive signal for vibrating the meniscus to such an extent that no ink droplets are ejected from the nozzle openings;
When the recording head is in a non-printing state, the first mode in which the second driving signal is applied to the piezoelectric vibrator at a cycle longer than the ink droplet ejection cycle; When switching from the printing state to the printing state, the second mode in which the second drive signal is applied to the piezoelectric vibrator continuously for a time longer than the application time in the first mode immediately before printing is selected. Means to
An ink jet recording apparatus comprising: The ink jet recording apparatus according to claim 1, wherein the duration of the second drive signal is set to coincide with the natural vibration period of the pressure generating chamber. An ink jet recording head having a pressure generating chamber formed by a nozzle plate having a nozzle opening and a diaphragm deformed by displacement of the piezoelectric vibrator;
A first drive signal for ejecting ink droplets in synchronization with an external timing signal, a second drive signal for vibrating the meniscus to such an extent that no ink droplets are ejected from the nozzle opening, and a meniscus for the nozzle opening are vibrated. A drive signal generating circuit capable of generating a third drive signal capable of inducing vibration having a smaller amplitude than that of the second drive signal;
A first mode in which the second drive signal is intermittently applied to the piezoelectric vibrator in a state where the ink jet recording head is in a print pause state and not sealed by a capping unit; and the ink jet recording head performs printing. Immediately before accelerating toward the possible speed and reaching the printing speed, the second drive signal is applied to the piezoelectric vibrator continuously for a time longer than the application time of the second drive signal in the first mode. When the ink jet recording head enters a standby state in the printing region, the third drive signal is applied to all the piezoelectric vibrators in accordance with the ink droplet ejection cycle, and ink droplet ejection is performed. Means for selecting a third mode in which the first drive signal is applied to the piezoelectric vibrator for discharging the ink droplets to eject ink droplets ;
An ink jet recording apparatus comprising: 4. The ink jet recording apparatus according to claim 3, wherein a duration time of the second drive signal and the third drive signal is set to coincide with a natural vibration period of the pressure generating chamber. 4. The ink jet recording apparatus according to claim 1, wherein the second drive signal and the third drive signal have rising and falling slopes corresponding to an environmental temperature. 5. 4. The ink jet recording apparatus according to claim 1, wherein voltages of the second drive signal and the third drive signal are changed according to an ejection amount of ink droplets during printing. 5. 4. The ink jet recording apparatus according to claim 1, wherein the second drive signal is applied to the plurality of nozzle opening rows with a certain time difference. 5. An ink jet recording head including a pressure generating chamber having a wall surface formed by a diaphragm that communicates with a nozzle opening and is deformed by displacement of a piezoelectric vibrator;
Capping means for sealing a nozzle opening of the ink jet recording head;
A first drive signal for ejecting ink droplets from the nozzle openings;
Drive signal generating means for generating a second drive signal for vibrating the meniscus to such an extent that ink droplets are not ejected from the nozzle openings;
When the ink jet recording head is in a non-printing state, the second drive signal is applied to the piezoelectric vibrator at a predetermined cycle so as to continue for a predetermined time, and printing is performed from a state where the movement of the ink jet recording head is stopped. Means for applying the second drive signal to the piezoelectric vibrator for a time longer than the predetermined time immediately before reaching a printable speed after being accelerated to a possible speed;
An ink jet recording apparatus comprising:

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