JP2000117993A - Ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recorder in which a trouble of taking a bubble into nozzle opening is reduced significantly and waste of ink is suppressed by increasing the flushing region. SOLUTION: The ink jet recorder comprises a recording head for ejecting an ink drop from a nozzle opening 15 by varying the pressure in a pressure chamber 17 communicating with the nozzle opening 15 according to a drive signal, wherein viscosity is lowered at a moment of turn on power by performing micro oscillatory operation for micro varying the pressure in the pressure chamber 17 prior to normal flushing thereby micro oscillating and diffusing thickened ink in the vicinity of the nozzle opening 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus having an ink jet recording head for forming dots on a recording medium by ejecting ink droplets from nozzle openings in accordance with print data. The present invention relates to an ink jet recording apparatus that recovers the ink droplet discharge capability of a nozzle opening by discharging ink droplets unrelated to the ink jet recording apparatus.

[0002]

2. Description of the Related Art In general, as shown in FIG. 11A, an ink jet recording head (hereinafter referred to as a "recording head") has a plurality of nozzle openings 40 (only one is shown in the drawing) and Pressure generating chamber 41 communicating with
And a piezoelectric vibrator 42 that abuts against an elastic wall 43 that constitutes a part of the pressure generating chamber. Then, the pressure in the pressure generating chamber 41 is changed by expanding and contracting the piezoelectric vibrator 42 in accordance with the print signal, and the ink 44 in the pressure generating chamber 41 is ejected as an ink droplet from the nozzle opening 40 by the pressure change. It is configured to be.

In order to improve the resolution of printing by ejecting ink droplets as small as possible when ejecting ink droplets with such a recording head, recently, a so-called "pulling" ejection method is used. Has become mainstream. In this “pulling”, as shown in FIGS. 11B and 11C, first, a voltage is applied to the piezoelectric vibrator 42 to contract it, and the meniscus 46 of the nozzle opening 40 is retracted to some extent. The piezoelectric vibrator 42 is returned to the original state, and the inside of the pressure generating chamber 41 is pressurized to discharge the ink droplet 45.

In the above-described recording head, when print data is lost and the recording head itself is in a rest state, the ink 44 near the nozzle opening 40 dries and clogs. Therefore, while the printing operation is not performed, the recording head is sealed with the cap. However, if the recording head is left for a long period of time while being sealed, the solvent of the ink 44 near the nozzle opening 40 evaporates little by little. As a result, troubles such as a difficulty in printing immediately and a decrease in print quality are likely to occur. Further, the nozzle opening 4 which continuously discharges the ink droplets 45 by the printing operation.
0 indicates that the new ink 44 is sequentially supplied and clogging hardly occurs, but the ink droplet 45
In the nozzle opening 40 where discharge of the ink is extremely low, the ink 44 in the vicinity of the nozzle opening 40 dries during printing, and the viscosity increases, and clogging is likely to occur.

To cope with such a problem, one of the preliminary operations before the start of printing is performed at the time when the recording apparatus is turned on or when a print signal is first input, regardless of printing. The ink droplet 45 is forcibly forced from each nozzle opening 40.
Is performed to eliminate the clogging of the nozzle opening 40 and execute a “flushing operation” or a “cleaning operation” for restoring the ink droplet ejection capability.

In the above-mentioned "flushing operation", a thickened ink 44 around the nozzle opening 40 is ejected in advance by applying a drive signal irrelevant to print data to the piezoelectric vibrator 42. The “cleaning operation” is performed when the nozzle opening 40 is not completely recovered only by the “flushing operation”.
By applying a negative pressure to each nozzle opening 40 with a suction pump, the thickened ink 44 in the pressure generating chamber 41 or the like is forcibly sucked in advance.

Here, the ink 44 around the nozzle opening 40 is
The degree of viscosity increase and clogging of the nozzle openings 40 increase as the time during which the recording head is left sealed with the cap (capping time) or the total printing time until the recording head is sealed with the cap becomes longer. The condition worsens. Therefore, the above "flushing operation" and "cleaning operation"
Is determined by, for example, a balance between the capping time and the total printing time as shown in FIG. 12, and the flushing operation is performed while the capping time or the total printing time is short (see FIG. 12). The flushing area), the cleaning operation is executed when the capping leaving time or the printing time becomes long (the cleaning area in the figure).

The condition of the flushing operation is as follows.
When a drive voltage is applied to the piezoelectric vibrator 42, it is normal to apply a voltage higher than the voltage at the time of printing at the highest frequency.

[0009]

However, in the above-mentioned conventional apparatus, if the flushing operation is performed near the boundary between the cleaning area and the flushing area, the viscosity of the ink 44 is further increased, so that the flushing is forcibly performed. When the ink 44 is ejected, the behavior of the meniscus 46 becomes extremely unstable, for example, as shown in FIG. 13, the meniscus 46 enters obliquely and deeply, and bubbles may be taken into the nozzle opening 40. Further, since a drive voltage higher than the voltage at the time of printing is applied to the piezoelectric vibrator 42 in order to discharge the thickened ink 44 more strongly, the ink 44 in the nozzle opening 40 is rapidly drawn. Similarly, the behavior of the meniscus 45 becomes unstable,
There is a possibility that the meniscus may enter obliquely and deeply and air bubbles may be taken into the nozzle opening 40.

As described above, when air bubbles are taken into the nozzle opening 40, the ink droplet 45 cannot be ejected from the nozzle thereafter, causing a fatal trouble as an ink jet recording apparatus.

On the other hand, in the cleaning operation, since the ink is forcibly sucked by the suction pump, the consumed ink amount is larger than that in the flushing operation. Therefore, in order to reduce the amount of ink consumed for eliminating clogging and increase the effective amount of ink that can be used for printing, and to reduce the volume of waste liquid, the flushing area is made as large as possible, and the area of thickening is as high as possible. It is desirable to eliminate clogging and the like by flushing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and greatly reduces troubles such as taking in air bubbles into a nozzle opening, and can increase a flushing area to reduce waste of ink. It is an object of the present invention to provide an expression recording device.

[0013]

In order to achieve the above object, an ink jet recording apparatus according to the present invention varies the pressure in a pressure chamber communicating with a nozzle opening in accordance with a drive signal, and the pressure fluctuation causes the nozzle to change. An ink jet recording apparatus including a recording head for ejecting ink droplets from an opening, wherein the pressure in the pressure chamber is slightly fluctuated prior to the flushing when the flushing timing comes. And

That is, the ink jet recording apparatus according to the present invention, when the flushing timing comes,
Prior to the flushing, the pressure in the pressure chamber is slightly fluctuated. For this reason, when the printing operation is not performed and the recording head is left for a long time with the cap sealed, or when the ink is thickened and clogged at the nozzle opening where the chance of discharging the ink droplet is extremely low. However, when the pressure in the pressure chamber is slightly fluctuated in advance, the meniscus at the nozzle opening and the viscous ink near the meniscus are minutely vibrated and diffused, and the ink viscosity is reduced. Thus, prior to the flushing, the viscosity of the thickened ink near the nozzle opening is reduced, and the flushing operation is performed in that state, so that the meniscus during the flushing operation is stabilized, and the nozzle during the flushing as in the related art is used. Almost no air bubbles are trapped in the opening.

In addition, conventionally, even ink whose viscosity has been increased to such an extent that it cannot be recovered by a cleaning operation is diffused in advance and the viscosity is reduced, so that the range in which the function can be fully recovered only by flushing is expanded. be able to. In other words, the flushing area can be greatly expanded as compared with the conventional case, the amount of ink consumed for eliminating clogging decreases, the amount of effective ink available for printing increases, and the volume of waste liquid can be reduced. it can.

In the ink jet recording apparatus of the present invention, when the pressure in the pressure chamber is made to fluctuate slightly within a range in which ink droplets are not ejected, wasteful ink is not consumed for eliminating clogging. In addition, the amount of effective ink that can be used for printing can be increased, and the volume of waste liquid can be reduced.

In the ink jet recording apparatus of the present invention, when the pressure in the pressure chamber is changed by the piezoelectric vibration of the piezoelectric vibrator, the driving voltage and the waveform of the piezoelectric vibrator are controlled to control the pressure chamber. Can be made to fluctuate minutely, and control of the minute fluctuation of pressure is easy.

In the ink jet recording apparatus of the present invention, when a driving voltage is applied to the piezoelectric vibrator to depressurize the pressure chamber and then pressurize to discharge ink droplets, the ink viscosity is reduced. As a result, the ink is ejected with a small pressure fluctuation, so that it is not necessary to particularly increase the driving voltage applied to the piezoelectric vibrator at the time of flushing, and the ink at the nozzle opening is rapidly drawn and remains as bubbles. Things are almost gone.

In the ink jet recording apparatus of the present invention, when the driving voltage of the piezoelectric vibrator when the pressure in the pressure chamber is slightly fluctuated is 10% to 30% of the driving voltage at the time of printing, it is increased to some extent. Even if the ink is viscous, it can be sufficiently diffused to lower the viscosity, and the ink can be prevented from being ejected due to a minute change in pressure.

In the ink jet recording apparatus according to the present invention, when the pressure in the pressure chamber is slightly fluctuated in response to a signal at the time of turning on the power or at the start of printing, the vicinity of the nozzle opening immediately before the printing is started. This is extremely effective because the thickened ink is diffused by a minute change in pressure to perform a flushing operation to recover the ink droplet ejection ability.

The ink jet recording apparatus of the present invention has a capping means for sealing the recording head, and a capping time measuring means for measuring a time when the recording head is sealed by the capping means. If the pressure in the pressure chamber is made to fluctuate slightly when the set value is exceeded, it is necessary to increase the viscosity so that clogging can be recovered only by the flushing operation without performing diffusion due to the minute fluctuation in pressure. In addition, since the minute fluctuation is not performed, the time required for the recovery of the ink droplet discharge capability is not inadvertently increased.

The ink jet recording apparatus according to the present invention includes a capping means for sealing the recording head and a printing time measuring means for measuring a printing time until the recording head is sealed by the capping means. When the pressure inside the pressure chamber is made to fluctuate slightly when the pressure exceeds the limit, if the viscosity increases enough to recover the clogging only by the flushing operation without performing diffusion due to the minute fluctuation of the pressure, Since it does not fluctuate, the time required for the recovery of the ink droplet ejection ability does not increase carelessly.

[0023]

Next, embodiments of the present invention will be described in detail.

FIG. 1 is a diagram showing an example of a peripheral structure of an ink jet recording apparatus to which the present invention is applied. This apparatus includes a carriage 1 on which an ink cartridge 7 is mounted on an upper part and a recording head 6 is attached on a lower surface, and a capping device 8 for sealing the recording head 6 or the like.

The carriage 1 includes a timing belt 2
, And is guided by a guide bar 4 to reciprocate in the paper width direction of the recording paper 5. A recording head 6 is attached to the carriage 1 on the surface (the lower surface in this example) facing the recording paper 5. Then, ink is supplied from the ink cartridge 7 to the recording head 6, and ink droplets are ejected onto the upper surface of the recording paper 5 while moving the carriage 1 to print images and characters on the recording paper 5 in a dot matrix. I have.

The capping device 8 includes a carriage 1
Is provided in a non-printing area within the moving range of the recording head 6, and the nozzle openings of the recording head 6 are sealed during printing suspension so as to prevent drying of the nozzle openings as much as possible. The capping device 8 also functions as a container for receiving ink droplets ejected from the recording head 6 by a flushing operation. Further, the capping device 8 is connected to a suction pump 9, and applies a negative pressure to a nozzle opening of the recording head 6 during a cleaning operation to suck ink from the nozzle opening.

FIG. 2 is a diagram showing an example of the recording head 6. The recording head 6 includes a base 11 and the base 1
Piezoelectric vibrator 13 accommodated in one accommodation chamber 12 so as to be able to vibrate
And a flow channel unit 14 fixed to the lower surface of the base 11
And

The flow path unit 14 has a nozzle opening 15
Is formed by a nozzle plate 16 having a hole formed therein, a thin diaphragm 21 elastically deformed, and a flow path forming plate 20 fixed between the nozzle plate 16 and the diaphragm 21 in a liquid-tight manner. . The flow path forming plate 20 has a pressure generating chamber 17 communicating with the nozzle opening 15, an ink chamber 18 receiving ink from the ink cartridge 7, and an ink supplying ink from the ink chamber 18 to the pressure generating chamber 17. A space corresponding to the supply path 19 is formed.

The piezoelectric vibrator 13 is mounted on a support substrate 22.
By being fixed inside, it is accommodated in the accommodation chamber 12 so as to be able to vibrate. The lower end of the piezoelectric vibrator 13 is connected to the island portion 2 of the diaphragm 21 of the flow path unit 14.
1a. In the figure, reference numeral 23 denotes a signal cable for sending a drive signal to the piezoelectric vibrator 13.

In the recording head 6, for example, printing is performed as follows. That is, first, when the piezoelectric vibrator 13 receives charge and contracts, the pressure generating chamber 17 expands, and the internal pressure decreases. Thereby, the nozzle opening 1
The meniscus formed in 5 is slightly drawn toward the pressure generating chamber 17, and the ink in the ink chamber 18 is supplied to the pressure generating chamber 17 through the ink supply path 19.

Then, after a lapse of a predetermined time, the piezoelectric vibrator 1
When the charge of No. 3 is discharged and the piezoelectric vibrator 13 returns to the original state, the pressure generating chamber 17 contracts and the internal pressure increases. As a result, the ink in the pressure generating chamber 17 is compressed and ejected from the nozzle openings 15 as ink droplets, and the ink droplets are ejected on the upper surface of the recording paper 5 to print an image or a character.

FIG. 3 is a diagram showing an embodiment of the ink jet recording apparatus of the present invention. In the figure, reference numeral 25 denotes a receiving buffer for receiving print data from a host (not shown), 26 denotes a bitmap generating means for converting the print data into bitmap data, and 27 temporarily stores the bitmap data. Print buffer.

Numeral 29 denotes a head driving means, which responds to a print signal from the print buffer 27, and
To perform a printing operation in which a drive voltage is applied to the recording head 6 to eject ink droplets. Further, when the flushing timing comes, a driving voltage independent of the print signal is applied to the piezoelectric vibrator 13 to execute a flushing operation for ejecting ink droplets from all the nozzle openings 15 of the recording head 6. Further, prior to the flushing operation,
A minute drive voltage is applied to the piezoelectric vibrator 13 to cause the piezoelectric vibrator 13 to vibrate finely, and to perform a fine vibration operation in which the pressure in the pressure generating chamber 17 is repeatedly and minutely fluctuated.

Numeral 32 denotes a pump driving means, which performs a cleaning operation for applying a negative pressure to the recording head 6 sealed in the capping device 8 by the suction pump 9 and forcibly sucking ink from all the nozzle openings 15. I do.

Numeral 28 denotes a carriage control means which moves the carriage 1 by the pulse motor 3 to scan the recording head 6 during printing, and positions the capping device 8 and the recording head 6 at the time of flushing operation or at the end of printing. Is controlled to move the carriage 1.

Reference numeral 34 denotes an idle timer, which is activated by detecting that the recording head 6 is sealed by the capping device 8 by a signal from the carriage control means 28 or the like, and seals the recording head 6 by the capping means 8. The capping leaving time (hereinafter, referred to as “leaving time”) left in the state of being left is measured. Reference numeral 35 denotes a print timer, which is started by detecting the start of printing based on signals from the head driving means 29 and the carriage control means 28, and then, after the recording head 6 is released from the capping device 8, sealed again in the capping device 8. Measure the total printing time until it is stopped. The sealing timer 34 and the printing timer 35 are reset when a signal is output.

Numeral 33 is a mode selection means, which receives a signal of the idle time and the total print time output from the idle timer 34 and the print timer 35, and executes a flushing operation based on a balance between the idle time and the total print time. A flush mode or a cleaning mode for executing a cleaning operation is selected (see FIG. 12), and a signal of the selected mode is output.

Numeral 30 denotes a vibration control means, which receives a signal from the mode selection means 33, applies a drive voltage to the piezoelectric vibrator 13 by the head driving means 29, and causes the piezoelectric vibrator 13 to expand and contract repeatedly to vibrate. And a micro-vibration operation that does not eject ink droplets from the nozzle opening 15;
The flushing operation of a large vibration for ejecting ink droplets from the nozzle opening 15 and the printing operation are controlled. Reference numeral 31 denotes a cleaning control unit, which receives a signal from the mode selection unit 33 and controls a cleaning operation by the pump driving unit 32.

Next, an example of the operation of the ink jet recording apparatus will be described with reference to the flowchart shown in FIG. In the figure, "S" means a step.

First, when the power is turned on or when printing is started,
The idle time is detected by the idle timer 34, and the total print time is detected by the print timer 35 (S1 and S2). Next, the mode selection unit 33 determines whether or not the reference time has elapsed based on a balance between the idle time and the total printing time (see FIG. 12) (S3). If the reference time has elapsed, the cleaning mode (the cleaning area in FIG. 12) is selected (S4). If the reference time has not elapsed, the flushing mode (the flushing area in FIG. 12) is selected (S7).

When the flushing mode is selected, a micro-vibration operation is performed prior to the flushing operation, as shown in FIG. That is, as shown in FIG. 6, the vibration control means 30 applies a drive voltage to the piezoelectric vibrator 13 such that an ink droplet is not ejected from the nozzle opening 15 to cause the piezoelectric vibrator 13 to vibrate finely. The drive signal of the piezoelectric vibrator 13 in the fine vibration operation is shown in FIG.
As shown in (b), the voltage is applied at a voltage V2 lower than the voltage V1 having a trapezoidal drive waveform for discharging a normal ink droplet. Also, the voltage gradient α or β during charging or discharging
Is set to a gradient suitable for fine vibration, more efficient vibration can be generated.

Further, by adjusting only the voltage gradients α and β of the normal drive signal so that the expansion / contraction speed of the pressure chamber becomes slower than usual, fine vibrations can be prevented so that ink droplets are not ejected. Can also be generated. For example, as shown in FIG. 8, the meniscus is set so that the gradients α ′ and β ′ are gentler than the voltage gradient of the normal drive signal, or the voltage gradient β ′ is set smaller than the voltage gradient α ′. Rapidly into the pressure chamber and the nozzle opening 1
The ink near 5 can be diffused and the meniscus can be pushed back to return gently and vibrate without ejecting ink droplets.

By the above-mentioned minute vibration operation, the pressure generating chamber 17 is repeatedly expanded and contracted in small increments, and the pressure in the pressure generating chamber 17 is minutely changed. As a result, the meniscus of the nozzle opening 15 and the thickened ink near the nozzle opening 15 are vibrated, and the thickened ink is diffused to the lower viscosity side, and the ink viscosity near the nozzle opening 15 is reduced. At this time, the piezoelectric vibration of the piezoelectric vibrator 13 causes
Since the pressure in 7 is varied, control of the micro-vibration operation is easy. After that, a flushing operation is performed to eject ink near the nozzle opening 15 whose viscosity has decreased to some extent (S9), and then a printing operation is performed (S6).

The driving voltage at the time of the above-mentioned micro-vibration operation is such that the ink is not ejected, and even if the ink is thickened to some extent, the ink is sufficiently diffused to lower the viscosity. Is preferably 10% or more and 30% or less, and it is effective that the frequency is as high as possible (in this example, about 10 kHz).

On the other hand, when the cleaning mode is selected, the cleaning operation is performed by the cleaning control means 31, the pump driving means 32 and the suction pump 9, and a negative pressure is applied to all the nozzle openings 15 of the recording head 6. The thickened ink in the vicinity of the nozzle opening 15 is forcibly sucked (S5), and thereafter, a printing operation is executed (S6).

As described above, according to the above-described ink jet recording apparatus, even if the ink near the nozzle opening 15 thickens and clogs, the micro-vibration operation is performed prior to the flushing operation. The thickened ink around 15 is diffused to lower the viscosity. Since the flushing operation is performed in that state, the meniscus during the flushing operation is stabilized, and the nozzle opening 1
There is almost no trouble that air bubbles are taken into the inside of the tube 5.

In addition, even if the ink is thickened to such an extent that it cannot be recovered by a cleaning operation, the ink is preliminarily diffused to lower the viscosity, so that the range in which the function can be recovered only by flushing is expanded. In addition, since the micro-vibration operation is performed without discharging ink droplets, wasteful ink is not consumed. Further, it is not necessary to increase the drive voltage applied to the piezoelectric vibrator 13 during the flushing, and there is almost no trouble that the ink in the nozzle opening 15 is suddenly drawn and bubbles remain.

FIG. 9 and FIG. 10 are views showing a second embodiment of the ink jet recording apparatus of the present invention. In this apparatus, a cleaning mode for executing a cleaning operation (a cleaning area in the figure), a flushing mode for executing only a flushing operation (a flushing area in the figure), and a micro-vibration operation are performed based on a balance between the idle time and the total printing time. After execution, a micro-vibration mode (micro-vibration + flushing area in the figure) in which a flushing operation is performed is selected. In this device, if the viscosity is thick enough to recover the clogging without performing the diffusion by the micro-vibration operation, the micro-vibration operation is not performed. Never do. Otherwise, it is the same as the first embodiment, and has the same operation and effect.

In each of the above embodiments, an example is shown in which the present invention is applied to an ink jet recording apparatus having a recording head 6 using a piezoelectric vibrator 13 which expands and contracts in the axial direction. However, the present invention is not limited to this. Instead, the present invention may be applied to a recording head that expands and contracts the pressure generating chamber 17 by flexural vibration, an ink jet recording apparatus having a bubble jet recording head, and the like. In this case, the same operation and effect can be obtained.

In each of the above embodiments, the micro-vibration operation is executed before the flushing operation. However, the micro-vibration operation may be executed before the cleaning operation. In this case, the same operation and effect can be obtained.

[0051]

As described above, according to the ink jet recording apparatus of the present invention, the printing operation is not performed, and the recording head is left unattended for a long period of time while being sealed with the cap, and the opportunity to eject ink droplets is extremely low. Even if the ink thickens at the low nozzle opening and causes clogging, the meniscus at the nozzle opening and the viscous ink near the nozzle opening vibrate and diffuse by minutely changing the pressure in the pressure chamber in advance. As a result, the ink viscosity decreases. Thus, prior to the flushing, the viscosity of the thickened ink near the nozzle opening is reduced, and the flushing operation is performed in that state. Almost no air bubbles are trapped in the opening.

Further, conventionally, even ink whose viscosity has been increased to such an extent that it cannot be recovered by a cleaning operation is diffused in advance to lower the viscosity, so that the range in which the function can be recovered sufficiently by flushing alone is expanded. be able to. In other words, the flushing area can be greatly expanded as compared with the conventional case, the amount of ink consumed for eliminating clogging decreases, the amount of effective ink available for printing increases, and the volume of waste liquid can be reduced. it can.

In the ink jet recording apparatus of the present invention, when the pressure in the pressure chamber is made to fluctuate slightly within a range in which ink droplets are not ejected, wasteful ink is not consumed for eliminating clogging. In addition, the amount of effective ink that can be used for printing can be increased, and the volume of waste liquid can be reduced.

In the ink jet recording apparatus of the present invention, when the pressure in the pressure chamber is changed by the piezoelectric vibration of the piezoelectric vibrator, the driving voltage and the waveform of the piezoelectric vibrator are controlled to control the pressure chamber. Can be made to fluctuate minutely, and control of the minute fluctuation of pressure is easy.

In the ink jet recording apparatus of the present invention, when a drive voltage is applied to the piezoelectric vibrator to reduce the pressure in the pressure chamber and then pressurize to eject ink droplets, the ink viscosity is reduced. As a result, the ink is ejected with a small pressure fluctuation, so that it is not necessary to particularly increase the driving voltage applied to the piezoelectric vibrator at the time of flushing, and the ink at the nozzle opening is rapidly drawn and remains as bubbles. Things are almost gone.

In the ink jet recording apparatus of the present invention, when the driving voltage of the piezoelectric vibrator when the pressure in the pressure chamber is slightly fluctuated is 10% or more and 30% or less of the driving voltage at the time of printing, it is increased to some extent. Even if the ink is viscous, it can be sufficiently diffused to lower the viscosity, and the ink can be prevented from being ejected due to a minute change in pressure.

In the case of the ink jet recording apparatus of the present invention, when the pressure in the pressure chamber is slightly fluctuated in response to a signal at the time of turning on the power or at the start of printing, the vicinity of the nozzle opening immediately before the start of printing is obtained. This is extremely effective because the thickened ink is diffused by a minute change in pressure to perform a flushing operation to recover the ink droplet ejection ability.

The ink jet recording apparatus of the present invention has capping means for sealing the recording head, and capping time measuring means for measuring the time during which the recording head is sealed by the capping means. If the pressure in the pressure chamber is made to fluctuate slightly when the set value is exceeded, it is necessary to increase the viscosity so that clogging can be recovered only by the flushing operation without performing diffusion due to the minute fluctuation in pressure. In addition, since the minute fluctuation is not performed, the time required for the recovery of the ink droplet discharge capability is not inadvertently increased.

The ink jet recording apparatus of the present invention has capping means for sealing the recording head and printing time measuring means for measuring a printing time until the recording head is sealed by the capping means. When the pressure inside the pressure chamber is made to fluctuate slightly when the pressure exceeds the limit, if the viscosity increases enough to recover the clogging only by the flushing operation without performing diffusion due to the minute fluctuation of the pressure, Since it does not fluctuate, the time required for the recovery of the ink droplet ejection ability does not increase carelessly.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of an ink jet recording apparatus to which the present invention is applied.

FIG. 2 is a cross-sectional view illustrating an example of an inkjet recording head.

FIG. 3 is a configuration diagram showing one embodiment of an ink jet recording apparatus of the present invention.

FIG. 4 is a flowchart illustrating an operation of the ink jet recording apparatus.

FIG. 5 is an explanatory diagram showing the operation of the ink jet recording apparatus of the present invention.

FIG. 6 is an explanatory diagram showing the operation of the ink jet recording apparatus of the present invention.

FIGS. 7A and 7B are diagrams showing an example of a driving signal of a piezoelectric vibrator of the ink jet recording apparatus, wherein FIG. 7A shows a normal waveform and FIG.

FIG. 8 is a diagram illustrating an example of a waveform of a drive signal during a minute vibration operation of a piezoelectric vibrator of the ink jet recording apparatus.

FIG. 9 is an explanatory diagram showing a mode selection state based on a capping leaving time and a printing time in the ink jet recording apparatus according to the second embodiment of the present invention.

FIG. 10 is a flowchart showing an operation of the ink jet recording apparatus.

11A and 11B are cross-sectional views illustrating a conventional ink jet recording head, where FIG. 11A shows a steady state, FIG. 11B shows a state where a piezoelectric vibrator is contracted, and FIG. 11C shows a state where ink droplets are ejected.

FIG. 12 is an explanatory diagram showing a mode selection state based on a capping leaving time and a printing time in a conventional ink jet recording apparatus.

FIG. 13 is an explanatory diagram showing a state of a meniscus during a flushing operation in a conventional ink jet recording apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Carriage 2 ... Timing belt 3 ... Pulse motor 4 ... Guide bar 5 ... Recording paper 6 ... Recording head 7 ... Ink cartridge 8 ... Capping device 9 ... Suction pump 11 ... Base 12 ... Storage chamber 13 ... Piezoelectric vibrator 14 ... Flow path unit 15 Nozzle opening 16 Nozzle plate 17 Pressure generating chamber 18 Ink chamber 19 Ink supply path 20 Flow path forming plate 21 Vibrating plate 21a Island part 22 Support substrate 23 Signal cable 25 Reception Buffer 26 Bitmap generating means 27 Print buffer 28 Carriage control means 29 Head driving means 30 Vibration control means 31 Cleaning control means 32 Pump driving means 33 Mode selection means 34 Leaving timer 35 Print timer

Claims (8)

[Claims] 1. An ink jet recording apparatus comprising: a recording head that varies a pressure in a pressure chamber communicating with a nozzle opening in accordance with a drive signal and ejects ink droplets from the nozzle opening by the pressure variation. An ink jet recording apparatus characterized in that the pressure in the pressure chamber is fluctuated slightly before the flushing when the timing of (1) comes. 2. The ink jet recording apparatus according to claim 1, wherein the pressure in the pressure chamber is slightly fluctuated within a range in which ink droplets are not ejected. 3. The ink jet recording apparatus according to claim 1, wherein the pressure in the pressure chamber is changed by the piezoelectric vibration of the piezoelectric vibrator. 4. The ink jet recording apparatus according to claim 3, wherein a driving voltage is applied to the piezoelectric vibrator to depressurize the pressure chamber, and then pressurize to discharge ink droplets. 5. The ink jet recording apparatus according to claim 3, wherein a driving voltage of the piezoelectric vibrator when the pressure in the pressure chamber is slightly fluctuated is 10% to 30% of a driving voltage at the time of printing. 6. The ink jet recording apparatus according to claim 1, wherein the pressure in the pressure chamber is minutely fluctuated in response to a signal at power-on or at the start of printing. 7. A printing apparatus comprising: capping means for sealing a recording head; and capping time measuring means for measuring a time when the recording head is sealed by the capping means.
The ink jet recording apparatus according to any one of claims 1 to 6, wherein the pressure in the pressure chamber is slightly changed when the capping time exceeds a set value. 8. A pressure chamber having a capping means for sealing a recording head and a printing time measuring means for measuring a printing time until the recording head is sealed by the capping means. The ink jet recording apparatus according to any one of claims 1 to 7, wherein the pressure is slightly fluctuated.