JPH0930007A - Ink jet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent clogging even when ink easy to form a film for printing of high quality is used. SOLUTION: An ink jet recording apparatus is equipped with a drive voltage generation circuit 31 generating a trapezoidal first drive voltage in synchronous relation to the timing signal from the outside, a drive circuit 32 outputting first drive voltage to a piezoelectric vibrator 17 corresponding to the printing signal from the outside and also outputting second voltage for generating small pulses of a degree not emitting ink droplets from nozzle orifices to the piezoelectric vibrator 17 held to a non-printing state over one cycle or more and a control means 30 stopping the application of small pulses when the application time of small pulses after the completion of printing exceeds a predetermined time. Fine vibration is applied to a meniscus in order to prevent the clogging of nozzle orifices without generating ink mist by applying small pulses when ink droplets are not emitted over one cycle or more and the application of small pulses is stopped at a point of time when printing is interrupted and the application of small pulses continues for a predetermined time or more to prevent the filming of ink at the nozzle orifices by fine vibration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for preventing clogging of nozzle openings of a printer using an on-demand type ink jet recording head.

[0002]

2. Description of the Related Art An on-demand type ink jet recording head is provided with a plurality of nozzle openings and pressure generating chambers communicating with the nozzle openings, and the pressure generating chambers are expanded and contracted in response to a print signal to generate ink drops. Is configured to occur. By the way, the ink droplets adhering to the recording medium may be bleeded depending on the quality of the paper or may be rubbed by coming into contact with other members, so that the solvent is prepared to volatilize and solidify as quickly as possible. For this reason, when the printing operation is interrupted, the ink solvent in the nozzle openings is volatilized and clogging occurs. Therefore, measures are taken to prevent evaporation of the ink solvent by mounting a cap on the nozzle openings. On the other hand, since new ink is supplied to the nozzle openings during the printing operation, there is less risk of clogging, but there is a great opportunity to eject ink droplets at specific nozzle openings, such as the nozzle openings at the upper and lower ends. Since it is low, clogging easily occurs.

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, and the piezoelectric vibrator drive signal is applied to the cap from all nozzle openings toward the cap. It has been proposed to perform a so-called flushing operation in which ink droplets are forcibly ejected, but this method requires interruption of the printing operation, and thus has a problem of extremely slowing the printing speed.

In order to reduce the frequency of such flushing operation as much as possible, ink droplets are ejected to a piezoelectric vibrator provided in a pressure generating chamber that communicates with a nozzle opening that does not generate ink droplets during a printing operation. Many technologies have been proposed to prevent clogging by applying a minute driving signal to such an extent that the meniscus in the vicinity of the nozzle opening is minutely vibrated (JP-A-55-123476 and JP-A-57-61).
576, U.S. Pat. No. 4,350,989).

According to this, although the interruption of the printing operation due to the flushing operation can be reduced and the reduction of the printing speed can be prevented, after ejecting the ink droplet, if the ink droplet is not ejected at the next timing, Since the minute vibration is applied after the ink droplet is ejected, there is a problem that the minute vibration is superimposed on the residual vibration of the meniscus caused by the ink droplet ejection to eject an unnecessary ink droplet.

In order to solve such a problem, an ink jet printer in which a meniscus of a nozzle opening is minutely vibrated at regular intervals after ejecting ink droplets as shown in US Pat. No. 5,329,293. Is proposed.

However, recently, in order to improve the printing density, it is necessary to form dots of a smaller size.
An ink that causes less bleeding on a recording medium, for example, an ink that contains a resin emulsion and promotes rapid film formation is used.

[0008] If such an ink that is easy to form into a film is used, and unnecessary microvibration is applied to the meniscus to prevent clogging, the ink solvent near the meniscus will easily volatilize and the film formation will be promoted and the nozzle opening will be clogged. There is a problem that causes.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to reduce the flushing operation as much as possible while preventing the printing speed from decreasing. An object of the present invention is to provide an ink jet apparatus that can prevent clogging of a nozzle opening due to microvibration even for ink that easily forms a film.

[0010]

In order to solve such a problem, a nozzle plate having a nozzle opening is formed,
An inkjet recording head including a pressure generating chamber formed by a vibration plate that is deformed by expansion and contraction of a piezoelectric vibrator,
A drive voltage generation circuit that generates a trapezoidal first drive voltage in synchronization with a timing signal from the outside, and outputs the first drive voltage to the piezoelectric vibrator in response to a print signal from the outside, A drive circuit that outputs a second voltage for generating a small pulse to the extent that an ink droplet is not ejected from the nozzle opening in synchronization with the timing signal to the piezoelectric vibrator in which the non-printing state has continued for one cycle or more, and A control means for stopping the application of the small pulse when the small pulse application time exceeds a predetermined time is provided.

[0011]

During the printing period, a small pulse is selectively applied to a nozzle opening that does not eject ink droplets for one cycle or more, and a meniscus vibrates to prevent clogging of the nozzle opening without causing ink mist. On the other hand, when the printing is interrupted and the application of the small pulse continues for a predetermined time or longer, the application of the small pulse is stopped to prevent the ink film formation at the nozzle opening.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments. FIG. 1 shows a structure around a printing mechanism of a printer of the present invention, showing an embodiment, in which reference numeral 1 is a carriage, and a pulse motor 3 is provided via a timing belt 2 to a pulse motor 3. The recording sheet 5 is connected and guided by the guide member 4 to reciprocate in the paper width direction of the recording sheet 5.

An ink jet recording head 6, which will be described later, is attached to the surface of the carriage 1 facing the recording paper 5, that is, the lower surface in this embodiment. The inkjet recording head 6 receives ink replenishment from an ink cartridge 7 mounted on the upper portion of the carriage 1, ejects ink droplets on recording paper in accordance with the movement of the carriage 1, forms dots, and performs recording. Print images and characters on paper.

Reference numeral 8 denotes a capping device, which is provided in the non-printing area and seals the nozzle opening of the recording head 6 during rest, while ink drops from the recording head 6 due to the flushing operation performed during the printing operation. To receive.

A cleaning means 9 is provided in the vicinity of the capping device 8 and is configured to wipe the surface of the nozzle plate of the recording head 6 with a blade or the like to wipe off the ink residue and paper dust on the surface of the nozzle plate. There is.

FIG. 2 shows an embodiment of the above-mentioned ink jet recording head with a sectional structure of one pressure generating chamber. In the drawing, reference numeral 10 is a nozzle plate, and nozzle openings 11 are formed. Further, reference numeral 12 is a flow path forming plate, which defines a through hole that defines the pressure generating chamber 13, and two ink supply ports 14 and 1 that communicate with both sides of the pressure generating chamber 13.
4 and the ink supply port 1
It is configured by providing through holes that partition two common ink chambers 15, 15 communicating with the ink cartridges 4, 14.

Reference numeral 16 is a vibrating plate, which is a thin plate that comes into contact with the tip of the piezoelectric vibrator 17 and elastically deforms.
The nozzle plate 10 and the nozzle plate 10 are liquid-tightly and integrally fixed to sandwich the gap to form the flow path unit 18.

A base 19 is provided with an accommodation chamber 20 for accommodating the piezoelectric vibrator 17 in a vibrating manner, and an opening 21 for supporting the flow path unit 18. The piezoelectric vibrator 17 has its tip exposed from the opening 21. And fixed with the fixed substrate 22,
The recording head is assembled by bringing the island portion 16a of the diaphragm 16 into contact with the piezoelectric vibrator 17 and fixing the flow path unit 18 in the opening 21.

With such a structure, when the piezoelectric vibrator 17 contracts and the pressure generating chamber 13 expands, the ink in the common ink chambers 15, 15 enters the pressure generating chamber 13 via the ink supply ports 14, 14. Pour in. When the piezoelectric vibrator 17 expands and the pressure generating chamber 13 contracts after a lapse of a predetermined time, the ink in the pressure generating chamber 13 is compressed and ink droplets are ejected from the nozzle openings 11 to form dots on the recording paper.

When a small pulse that does not cause ink droplets to be ejected is applied to the piezoelectric vibrator 17 to contract the piezoelectric vibrator 17 by a small amount, the pressure generating chamber 13 also slightly expands, so that the meniscus near the nozzle opening 11 is expanded. Is the pressure generation chamber 13
When the piezoelectric vibrator 17 is returned to the original state, the pressure generating chamber 13 contracts and the meniscus is slightly pushed back toward the nozzle opening 11 side.

By thus applying the small pulses to the piezoelectric vibrator 17 periodically in accordance with the printing timing,
It is possible to vibrate the meniscus in the vicinity of the nozzle opening by a small amount. Such vibration of the meniscus promotes the replacement of the ink in the vicinity of the nozzle opening with the ink in the pressure generating chamber 13, which is useful for preventing clogging.

In the present invention, in order to reduce the ink bleeding on the recording paper and form fine dots to improve the printing quality, the ink which is quickly formed into a film on the recording medium is used. As such an ink, for example, an ink having a composition of pigment 2 wt% resin emulsion 15 wt% diethylene glycol 5 wt% multitose 7 wt% surfactant 2 wt% pure water balance is desirable.

This ink has a viscosity of 3 to 5 mP at room temperature.
a ・ S and larger than normal ink, but surface tension is 3
0 to 50 mN / m, which is smaller than ordinary ink,
The ink droplets that have landed on the recording paper have a small spread,
Moreover, since the resin emulsion contained as a component is cured to form a film quickly, bleeding on the recording medium is extremely reduced, and especially in color printing, it is possible to prevent color mixture of inks and obtain high color development. it can.

FIG. 3 shows an embodiment of a control device for driving the above-described recording head. In the figure, reference numeral 30 is a control means, which receives a print command signal and print data from a host and drives the drive which will be described later. The voltage generation circuit 31, the drive circuit 32, and the carriage drive circuit 33 are controlled to execute the printing operation, and flushing is performed or application of a small pulse during the pause period is performed by the time measurement data of the timer unit 34 described later. It controls and further cleans the recording head 6.

The drive voltage generating circuit 31 includes a nozzle opening 11
Is configured to generate a first trapezoidal wave having a voltage value necessary for ejecting an ink droplet from.

The drive circuit 32 selectively applies the drive voltage of the drive voltage generation circuit 31 to the piezoelectric vibrator 17 corresponding to the print data, and the piezoelectric vibration of the nozzle opening in which ink droplets are not ejected for at least one cycle or more. The drive voltage of the drive voltage generation circuit 31 is applied to the child 17 as a small pulse.

Reference numeral 35 denotes a print timer for measuring the duration of the printing operation, which is activated by the start of printing and reset by the flushing operation. Reference numeral 36 is a pause timer, which is backed up by a battery or the like so as to be able to keep time even after the main power is turned off, and when the printing operation is stopped and the recording head 6 is sealed by the capping device 8, the time counting is started. In addition, it is configured to be reset when printing is started. A small pulse timer 37 starts counting at the time when a small pulse for vibrating the meniscus by a small amount at the nozzle opening is applied, and is reset at the time when the printing operation is started.

Reference numeral 38 denotes a power-off timer, which starts from the time when the power switch detection means 39 detects that the power switch SW of the box is off, and after the time required to seal the recording head 6 with the capping device 8 has elapsed. A signal is output to deactivate the relay 40 to cut off the main power supply to the device.

FIG. 4 shows an embodiment of the drive voltage generating circuit 31 described above. In the figure, reference numeral 50 is a one-shot multivibrator for converting a timing signal from an external device into a pulse signal of a constant width. The positive and negative signals are output from the output terminal in synchronization with the signal. The base of the NPN type transistor 51 is connected to one terminal, and the PNP type transistor 52 is connected to this, and when the timing signal is input, the capacitor 53 is connected until the power source voltage VH reaches approximately the voltage VH. Charge with a constant current Ir.

An NPN-type transistor 58 is connected to the other terminal of the one-shot multivibrator 50, and when the timing signal is switched, the transistor 52 is turned off, and instead, the transistor 58 is turned on and the capacitor 53 is turned on. It is discharged at a constant current If until the electric charge charged at the voltage drops to approximately zero volt.

That is, when the base-emitter voltage of the transistor 54 is VBE54 and the resistance value of the resistor 56 is Rr, the charging current Ir is Ir = Vbe54 / Rr, and when the capacitance of the capacitor 53 is C0, the charging voltage rises. The time Tr becomes Tr≈C0 × VH / Ir.

On the other hand, as for the discharge current If of the drive signal, the base-emitter voltage of the transistor 55 is VBE55 and the resistance 5 is
If the resistance value of 7 is Rf, If = Vbe55 / Rr, and the fall time is Tf.apprxeq.C0.times.VH / If.

As a result, the terminal voltage of the capacitor 53 becomes
As shown in FIG. 6 (V), the trapezoidal waveform has a region that rises at a constant gradient, a saturation region that holds a constant value, and a region that descends at a constant gradient. This capacitor 5
The terminal voltage of No. 3 is current-amplified by the transistors 59 and 60, and is transmitted from the terminal 61 to the piezoelectric vibrators 17, 17, 17 respectively.
It is output as a drive signal to.

Next, the operation of the drive voltage generating circuit 31 described above will be described. When the timing signal is input from the control means 30, the transistors 52 and 58 are turned on / off to output a drive signal having a trapezoidal voltage waveform. On the other hand, since the switching transistors T, T, T, ... Connected to the piezoelectric vibrator 17 to be printed are turned on by the drive circuit 32 described later, they are charged to the voltage VH by the drive signal. It will be.

As a result, the voltage signal generated in the drive voltage generating circuit 31 flows into the piezoelectric vibrator 17, and the piezoelectric vibrator 17
Is charged at a constant current. As a result, the piezoelectric vibrators 17, 17, 17, ... Which should eject ink droplets for printing contract and the pressure generating chamber 13 expands.

After a lapse of a certain time, the transistor 58 is turned on and the capacitor 53 is discharged, so that the electric charges of the piezoelectric vibrators 17, 17, 17 ... The pressure generating chamber 13 contracts due to expansion of 17, 17, ..., And ink droplets are ejected from the nozzle openings 11.

On the other hand, when the print data is not input for one cycle or more, the corresponding 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, the piezoelectric vibrators 17, 17, 17 are charged by the voltage from the drive voltage generating circuit 31, but the pulse signal falls during the charging, so that the switching transistors T, T, T ... Are turned off. The charging is completed at the voltage Vs up to this point.

As described above, in the state of being charged with the voltage Vs,
The transistor 58 turns on and the piezoelectric vibrators 17 and 1
When the electric charges 7, 17, ... Are discharged, the electric charges are extended by an amount proportional to the charging voltage Vs.

As a result, the piezoelectric vibrator 17 is shown in FIG.
As shown in FIG. 7, the pressure generation chamber 13 is expanded based on the voltage VS smaller than that at the time of printing, and the expansion sufficient to cause the ink droplets to fly from the nozzle opening 11 cannot be caused. It is possible to prevent the generation of an ink film in the vicinity of the nozzle opening 11 in the non-printing state in which the meniscus in the vicinity of the nozzle opening 11 is contracted to give a minute vibration.

Hereinafter, the piezoelectric vibrator 17 belonging to the nozzle opening for forming a dot in accordance with the timing signal is charged and discharged with a voltage capable of generating an ink droplet, and when print data is not input for one cycle or more. Is charged and discharged with a low voltage Vs that does not cause ink droplets to fly.

FIG. 5 shows an embodiment of the drive circuit 32 described above. Reference numeral 71 in the drawing is a shift register, which is constituted by flip-flops F1, F1, F1, ... The print data is sequentially transferred according to the shift clock.

Reference numeral 70 denotes a latch circuit, which is a shift register 7 in which flip-flops F2, F2, F2 ...
The signal from 1 is latched by the latch signal, and the piezoelectric vibrator 1
Each switching T connected to 7, 17, 17
A selection signal is output to T, T ....

72 is a switching means, which has two input terminals A,
B, the print data is input to the terminal A, and the terminal B
The print data to be printed at the next timing and a signal obtained by inverting the print data of the current print output from the shift register 71 by the inverter 73 are input via the OR gate 74, and are selected from the control means 30. Print by signal,
Alternatively, the data input for applying a small pulse can be selected.

Next, the operation of the drive circuit 32 will be described with reference to the timing chart of FIG. At the (n-1) th printing cycle, which is one cycle before the printing target cycle (nth printing cycle), the terminal B of the switching means 72 is selected by the selection signal, and the printing target data of all the nozzle openings is shift clocked. To the shift register 71 in synchronism with.

Then, the time tn-1 at which the trapezoidal drive voltage signal output in synchronization with the timing signal generated each time the recording head 6 moves by a predetermined distance reaches the ground level.
At the same time, a latch signal is output, and the data stored in the shift register 71 is latched by the latch circuit 70 all at once,
The conduction of each switching transistor T, T, T ... Is controlled.

That is, the switching transistor T of the nozzle opening that ejects ink droplets in the immediately preceding printing cycle ((n-1) th printing cycle) and does not eject ink droplets in the next printing cycle (nth printing cycle). Is selectively made non-conductive, the other switching transistors T of the nozzle openings are made conductive, and this state is maintained until the time tn at which a latch signal is subsequently input to the latch circuit 70, and the print target is printed. The corresponding piezoelectric vibrator 1 via the switching transistor T in the conductive state in the nth printing cycle of
Are charged to the voltage Vs.

After the data is latched at the time point tn-1, the terminal A of the switching means 72 is selected by the selection signal, and the data to be printed is again synchronized with the shift clock and stored in the shift register 71 as described above. Output at time tn
Then, only the print target data is latched in the latch circuit 70.

As a result, when the print data is data for ejecting ink droplets, the piezoelectric vibrators 17, 17, ... Are continuously charged to the voltage VH, and if the ink droplets are not ejected, or if the data is not ejected. The charging of the piezoelectric vibrators 17, 17, ... While charging is stopped, and the voltage VS is maintained thereafter.

After that, the driving voltage signal suddenly falls, so that the piezoelectric vibrator 1 charged to the voltage VH
The electric discharge of 7, 17, ... Causes the pressure generating chamber 13 to contract and ejects an ink droplet from the nozzle opening 11. On the other hand, the piezoelectric vibrators 17, 1 that have been charged to the voltage VS
7 also discharge at this voltage VS, but due to the low voltage value, they do not reach the point where ink droplets are ejected, and the meniscus in the vicinity of the nozzle opening 11 is simply vibrated.

According to the drive circuit 32 having such a configuration, as shown in FIG. 10, a small pulse (Fig. (II
Since I)) is applied, the vibration of the meniscus after ink droplet ejection is not amplified, and the generation of ink mist can be prevented.

The application of the above-mentioned small pulse is carried out for a certain period of time after the print data, which will be described later, has disappeared, or even when the carriage is stopped, such as during the printing process, during the conveyance of the recording paper. In such a case, the timing signal is virtually output, and the drive circuit 32 outputs data that does not eject ink droplets as print data.
It is realized by outputting to.

Next, the operation of the entire apparatus configured as described above will be described based on the flowcharts shown in FIGS. 7 to 9. When the power switch SW of the box is turned on (Fig. 7
Step a), the control means 30 checks the rest time of the rest timer 36, moves the carriage 1 to the home position when a predetermined time, for example, 6 hours or more has elapsed, and performs cleaning according to the length of the rest time. (Figure 7
Step b), reset the sleep timer 36 and restart it (step c in FIG. 7).

With no print command input (step D in FIG. 7), the recording head 6 is not sealed by the capping device 8 (step E in FIG. 7), and a small pulse is applied (step S7 in FIG. 7). ), Small pulse timer 3
When 7 has passed the predetermined time (step in FIG. 7), the application of the small pulse is stopped (step in FIG. 7), the small pulse timer 37 is reset (step in FIG. 7), and the print command is output. Wait for input (Figure 7 step
D).

Further, the recording head 6 is a capping device 8
If the small pulse is not applied (Fig. 7 Step E), it is not sealed (Fig. 7 Step E).
(F) It is investigated whether or not the pause timer 36 has passed a predetermined time.
), Perform cleaning (step 7 in Figure 7),
The recording head 6 is sealed by the capping device 8 (see FIG.
Step W) and reset the sleep timer 36 (see FIG. 7).
Step c) Wait for input of print command (step d in Fig. 7). If the elapsed time of the pause timer 36 does not exceed the predetermined time (step 7 in FIG. 7), the print command is input as it is (step 7 in FIG. 7).
D).

On the other hand, when a print command signal is input (see FIG. 7).
Step d), it is determined whether or not the recording head 6 is sealed by the capping device 8 (step C in FIG. 7), and if it is opened, the pause time is determined based on the data of the pause timer 36. If the predetermined time or more has not elapsed (step 7 in FIG. 7), a flushing operation is performed to eject a predetermined number, for example, 200 drops of ink from each nozzle opening 11 (step 7 in FIG. 7).

After the flushing operation, the control means 30 applies a small pulse to the recording head 6 (step) to vibrate the meniscus of the nozzle opening 11 slightly. Then, the pause timer 36 is reset, the small pulse timer 37 is started, and the print timer 35 is further started (step S in FIG. 7) to wait for the print data to be continuously input.

On the other hand, the capping device 8 for the recording head 6
If the release time from is more than a predetermined time (Fig. 7
After performing the cleaning (step yo) (Fig. 7)
Step S), a small pulse is applied to the recording head 6 (step S in FIG. 7), the meniscus of the nozzle opening 11 is slightly vibrated, the pause timer 36 is reset, the small pulse timer 37 is started, and the printing timer Three
Start 5 (step 7 in FIG. 7) and wait for input of print data.

On the other hand, when a print command is input (see FIG. 7).
Step D), when the recording head 6 is sealed by the capping device 8 (step C in FIG. 7),
The recording head 6 is released from the capping device 8 (see FIG.
Step N) Cleaning is performed (Step N in FIG. 7), a small pulse is applied to the recording head 6 (Step S), and the meniscus of the nozzle opening 11 is slightly vibrated.

Then, the pause timer 36 is reset, the small pulse timer 37 is started at the same time, and the print timer 35 is started (step S in FIG. 7) to wait for the input of print data.

When the print preparation is completed based on the print command and the print data is input, the control means 30 waits until the elapsed time of the small pulse timer 36 reaches a predetermined time, for example, 20 seconds (step b in FIG. 8). , Execute printing (Fig. 8
Step).

When the time measured by the small pulse timer 36 reaches a predetermined time, for example, 20 seconds during printing (step 8 in FIG. 8).
A), the control means 30 moves the recording head 6 to a flushing position, that is, a position facing the capping device 8 in accordance with the movement of the recording head 6 to the home position side (FIG. 8 Step B), and a predetermined number, For example, ink droplets of 60 dots are ejected to execute the regular flushing operation (step C in FIG. 8). When the flushing operation is completed, the small pulse timer 37 is reset and then the time counting operation is executed (step d in FIG. 8).

When print data is present and printing is to be executed subsequently (step E in FIG. 8), when the continuous printing time measured by the printing timer 35 is a predetermined time, for example, 2 hours or less ( In step F of FIG. 8, the print data that is continuously input is printed (step of FIG. 8).

When the printing time becomes longer and exceeds 2 hours (step F in FIG. 8), the control means 30 suspends the printing operation and moves the recording head 6 to the standby position (step CH in FIG. 8). ) Cleaning is performed (step 8 in FIG. 8), and the print timer 35 is restarted after the cleaning is completed (step 8 in FIG. 8).

When printing of all print data is completed in this way (step E in FIG. 8), the control means 30
The pause timer 36 is started, and the time counting operation of the print timer 35 is stopped (step 8 in FIG. 8), and the process jumps to step (d) in FIG. When printing of all print data is completed in this way (see step in FIG. 8).
(E) Since a small pulse is applied to the recording head 6 to prevent the nozzle openings from being clogged, printing is possible even when print data is subsequently input.

When the print command is not input (step D in FIG. 7), the recording head 6 is not yet sealed by the capping device 8 (step E in FIG. 7), and the small pulse is applied (step S in FIG. 7). F), small pulse timer 3
7 is applied for a predetermined time or more (see FIG.
And stop applying the small pulse (Fig. 7 step
H), reset the small pulse timer 37 (step in FIG. 7), and wait for input of print command (step in FIG. 7).
D).

As a result, volatilization of the ink solvent due to unnecessary minute vibration of the meniscus during a long waiting time after completion of printing is prevented, and clogging of a recording head using an ink that is particularly prone to film formation is prevented. be able to.

When the power switch SW is operated in the standby state to instruct power cutoff (step B in FIG. 9), the control means 30 detects whether or not the recording head 6 is still sealed by the capping device. If the capping is not performed (step B in FIG. 9), the cleaning of the recording head 8 is performed by the cleaning device 9 (step C in FIG. 9), and then sealing is performed by the capping device 8 (step D in FIG. 9).

When it is confirmed that the recording head 6 is capped in this way, the control means 30
Starts the power-off timer 38, and the print timer 3
5, the pause timer 36, and the small pulse timer 37 are reset (step E in FIG. 9). When the power-off timer 38 times out (step in FIG. 9)
F) Deactivate the relay 40 and cut off the power supply.

[0069]

As described above, in the present invention,
An ink jet recording head having a pressure generating chamber formed by a nozzle plate having a nozzle opening and a vibrating plate that is deformed by expansion and contraction of a piezoelectric vibrator, and a trapezoidal first head in synchronization with a timing signal from the outside. A drive voltage generating circuit that generates a drive voltage of 1 and a first drive voltage that corresponds to a print signal from the outside and that is output to the piezoelectric vibrator.
A drive circuit that outputs a second voltage for generating a small pulse to the piezoelectric vibrator in which the non-printing state continues for one cycle or more, in synchronization with the timing signal, and a small voltage after the printing is completed. Since the control means for stopping the application of the small pulse when the pulse application time exceeds the predetermined time is provided, the small pulse is applied to cause the ink mist when the ink droplet is not ejected for one cycle or more during the printing period. Not only can vibration of the meniscus be applied to prevent clogging of the nozzle opening without causing it, but application of the small pulse is stopped when printing is interrupted and application of the small pulse continues for a specified time or longer. As a result, it is possible to prevent clogging of the nozzle openings even with respect to the ink that easily forms a film.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an inkjet recording apparatus to which the present invention is applied.

FIG. 2 is a cross-sectional view showing one embodiment of an ink jet recording head.

FIG. 3 is a block diagram of an apparatus showing one embodiment of the present invention.

FIG. 4 is a circuit diagram showing an embodiment of the same drive voltage generating circuit.

FIG. 5 is a circuit diagram showing an embodiment of the above drive circuit.

6 (I) to (VII) are waveform charts showing the operation of the above-mentioned apparatus.

FIG. 7 is a flowchart showing a process from power-on to printing start in the operation of the above apparatus.

FIG. 8 is a flowchart showing a printing step in the operation of the above apparatus.

FIG. 9 is a flowchart showing a power interruption step in the operation of the above apparatus.

10 (A) to (III) respectively show a printing operation,
FIG. 6 is a waveform diagram showing a voltage applied to the piezoelectric vibrator during the rest period.

[Explanation of symbols]

 6 Inkjet Recording Head 8 Capping Device 9 Cleaning Device 11 Nozzle Opening 13 Pressure Generation Chamber 17 Piezoelectric Vibrator 34 Timer Means

Claims (3)

[Claims] 1. An ink jet recording head having a pressure generating chamber formed by a nozzle plate having a nozzle opening and a vibrating plate deformable by expansion and contraction of a piezoelectric vibrator, and an ink jet recording head synchronized with a timing signal from the outside. Drive voltage generation circuit for generating a trapezoidal first drive voltage, a first drive voltage corresponding to a print signal from the outside to the piezoelectric vibrator, and a nozzle opening synchronized with a timing signal. Drive circuit for outputting a second voltage for generating a small pulse to the extent that the ink droplets are not ejected to the piezoelectric vibrator in which the non-printing state continues for one cycle or more, and a small pulse application time after the printing is completed for a predetermined time. An ink jet recording apparatus comprising a control means for stopping the application of the small pulse when the number of pulses exceeds. 2. The drive circuit applies the small pulse to the piezoelectric vibrator based on a logical sum of data obtained by inverting print data currently printed and print data to be printed at the next print timing. The inkjet recording apparatus according to claim 1. 3. The control means applies the small pulse after performing a flushing operation when the inkjet recording head has been released from the capping device for a predetermined time or longer at the time when a print command is input from the outside. The ink jet recording apparatus according to claim 1, wherein the input of print data is waited for.