JPH10119265A - Ink jet head and method for removing air bubble therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively remove air bubbles from a common ink chamber of a piezoelectric type ink jet head having a plurality of ink discharge pressure chambers and the common ink chamber communicating the pressure chambers. SOLUTION: A vibrating means 9 is provided on the outer wall 38 of a common ink chamber 4 of an ink jet head, the outer wall 38 is caused to vibrate in ultrasonic wave by virtue of the vibrating means 9, so as to draw ink through a nozzle hole, with the use of a suction means 13 provided outside the ink jet head. Through the vibration of the outer wall 38 in ultrasonic wave, air bubbles attached on the inner wall of the common ink chamber 4 are released therefrom, discharged to the outside of the ink jet head by being entrained into the ink stream, thereby preventing any trouble in ink discharge which is possibly caused due to air bubbles. A suction means 13 employs only a restoration device which is indispensable for a conventional ink jet head, thus avoiding a complication in the structure of an ink jet head.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer, and more particularly to an on-demand type piezoelectric ink jet head.

[0002]

2. Description of the Related Art On-demand type printers using a piezoelectric ink jet head have advantages such as simple structure, relatively high speed, low noise recording, and easy color recording. It's being used. Such an ink jet head performs recording by intermittently discharging ink from the pressure chambers based on a drive signal. In order to increase the recording speed, it is general to provide a large number of pressure chambers in one ink jet head. is there. It has a plurality of pressure chambers and a common liquid chamber communicating with the pressure chambers, and deforms the outer wall of the pressure chambers by piezoelectric driving of the piezoelectric member, pressurizes the pressure chambers, and discharges ink from nozzle holes communicating with the pressure chambers. And make a record such as printing. FIG. 10 is a structural view of such a conventional ink jet head. 101 is a pressure chamber, 102 is a common liquid chamber, 103 is an outer wall, 104 is a nozzle hole, 105 is a piezoelectric element for a pressure chamber, 106 is a drive circuit, and 107 is an ink storage means.

[0003]

However, in such an ink jet head having a structure in which the pressure chamber and the common liquid chamber are provided, in order to increase the pressure in the pressure chamber at the time of ink ejection,
For the purpose of restricting the backflow of the ink, the entrance 108 from the common liquid chamber 2 to the pressure chamber 1 is often narrowed as shown in FIG. In this case, relatively large air bubbles 109 are likely to adhere to corners and the like deviating from the flow path in the common liquid chamber. When the attached air bubbles are small, the adhesive force is weak and can be discharged to the outside by the flow of ink, but when the air bubbles are relatively large, the adhesive force is strong and it is difficult to discharge to the outside even by the suction operation by the recovery device. It is. The attached air bubbles dissolve a part of the air in the air bubbles at the molecular level in the ink and increase the air content of the ink. When the turbulence occurs, the ink flows in the pressure chambers due to the ink ejection and suction operations, and becomes apparent as fine bubbles, and obstructs the pressurization of the pressure chambers, thereby obstructing or preventing the ejection of the ink. By the way, water-soluble ink and the like are basically capable of dissolving air in the ink, and even if the ink is defoamed before being supplied to the pressure chamber, air will be mixed in when replacing the ink cassette. It's easy to do. Even when the ink cassette is not used, air permeates from the outer wall of the polymer or the like in the supply path from the ink tank, and air is easily mixed.
In addition, even if the above-described defoaming is performed, the air component in the ink cannot be completely reduced to 0%.
Potentially contains some air. When the direction of ink flow changes in a short cycle in the opposite direction, or when the cross-sectional area of the flow path changes abruptly, cavitation occurs due to turbulence, and latent air components become bubbles. It is often the case that it becomes apparent. In any case,
It is almost impossible to eliminate bubbles in the common liquid chamber. In addition, in the corners and the like in the common liquid chamber, it is not unusual for bubbles to grow to have a size that cannot be ignored because other bubbles overlap with the bubbles. In such a case, the above problem occurs.

As a means for solving such adhesion of air bubbles, a means described in Japanese Patent Publication No. 62-9427 is known. In this means, a relay section is provided between the pressure chamber and the ink tank, and a branch pipe that rises vertically from the relay section and communicates with the atmosphere is provided, and an ultrasonic wave that vibrates the relay section and the branch pipe is provided. An ink jet head is constituted by providing an oscillator. When the relay section and the branch pipe are vibrated, bubbles generated in the relay section float on the branch pipe by buoyancy without being attached to the relay section and are discharged into the atmosphere. However, since the pressure in the relay section is equal to the atmospheric pressure, the pressure is transmitted to the pressure chamber, and even in a state where the pressure chamber is not pressurized by the piezoelectric element, there is a problem that the ink leaks from the nozzle hole and drips.

As a means for improving this point, Japanese Patent Publication No. Sho 62
No. 9427 is known. This means is, roughly speaking, a suction pump attached to the tip of the branch pipe. By operating the suction pump constantly, a negative pressure is applied to prevent the ink leakage. However, in this case, the head becomes heavy, which is disadvantageous in performing high-speed printing. In addition, the equipment becomes complicated and large, and the manufacturing cost and power consumption increase.
It is disadvantageous for practical use.

The present invention solves the above-mentioned problems of the prior art, and does not provide a special suction device in the head and does not cause ink to leak from the nozzle hole, so that air bubbles adhering to the common liquid chamber can be eliminated. It is an object of the present invention to reliably remove and discharge the ink so that the ink discharge operation can be performed normally by using a head having a small and simple structure advantageous for high-speed printing.

[0007]

As a first means for solving the above problems, the present invention comprises a plurality of pressure chambers,
An ink jet head having a common liquid chamber communicating with the pressure chamber, deforming and pressurizing the outer wall of the pressure chamber by piezoelectric driving, and discharging ink from nozzle holes communicating with the pressure chamber to perform printing, A vibration means for defoaming ink is provided on the outer wall.

As a second means for solving the above-mentioned problems, the present invention has a plurality of pressure chambers and a common liquid chamber communicating with the pressure chambers, and deforms the outer wall of the pressure chambers by piezoelectric driving. By pressurizing, by the vibrating means of the ink jet head, a vibrating means for defoaming the ink is attached to an outer wall of a common liquid chamber of the ink jet head which performs printing by discharging ink from a nozzle hole communicating with the pressure chamber, While vibrating the outer wall, air bubbles in the ink are sucked together with the ink from the nozzle holes by suction means separate from the ink jet, and the ink is defoamed.

As a third means for solving the above-mentioned problems, the present invention is characterized in that in the first means, the outer walls of the pressure chamber and the common liquid chamber are constituted by a common diaphragm, and the vibrating means is provided on the outer wall of the common liquid chamber. A piezoelectric member is joined.

[0010] As a fourth means for solving the above-mentioned problems, the present invention provides that the defoaming of the ink in the second means is performed at least during the recovery operation by using an ink-jet head recovery device as a suction means. It is characterized by.

According to the above-described first means, the ink jet head can be constructed without providing a special suction means in the pressure chamber. Therefore, the structure of the head is simplified. In particular, when a piezoelectric member is provided as a vibrating means as in the third means, the head can be configured to be small and light, so that printing can be performed at a high speed and the apparatus can be manufactured with high speed. It is easy to respond to miniaturization and thinning.

According to the second means, the outer wall is vibrated by vibrating means attached to the outer wall of the common liquid chamber, and the bubbles are divided and finely divided as described later, while being separated from the ink jet. The suction means provided in the nozzle sucks out bubbles in the ink together with the ink from the nozzle holes and removes the ink, so that the suction means is not provided in the head itself, and the suction means is not provided in the head itself. By defoaming the ink, the problem of air bubbles adhering to the common liquid chamber can be solved. In addition, according to the fourth means, the recovery device which is essentially indispensable for the recovery of the head can be used also as the suction means, so that the device is not complicated, increased in size and cost, and is practically used. Becomes easier.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 and FIG. 2 are cross-sectional views perpendicular to and parallel to the longitudinal direction of a pressure chamber of a main portion (referred to as a head main body 1) of the ink jet head of the present embodiment. The liquid chamber main body 2 is provided with a plurality of grooves forming a space of the pressure chamber 3, a depression forming a space of the common liquid chamber 4 communicating with the grooves, and an ink supply path 5 communicating with the common liquid chamber 4. Liquid chamber body 2
A common diaphragm 6 forming an outer wall 38 of the pressure chamber 3 and the common liquid chamber 4 is attached to the lower surface of the pressure chamber 3. The piezoelectric elements for pressure chambers 8 laminated on the base 7 are joined to each other so as to correspond to each pressure chamber.
Slit processing is performed, and the upper surface is joined to the diaphragm 6 at a position facing each pressure chamber 3. The vibrating piezoelectric element 9 is joined to the diaphragm 6 at a position facing the common liquid chamber 4. The electrodes of the pressure chamber piezoelectric element 8 and the vibration piezoelectric element 9 are connected to the FPC 10 by a conductive member such as a conductive adhesive.
Connect to the top line. This lead wire connects the electrodes of the pressure chamber piezoelectric element 8 and the vibration piezoelectric element 9 to a printing drive circuit (not shown) and a vibration drive circuit (to be described later), respectively. Here, the print drive circuit is a known one.

FIG. 3 shows an assembly in which the head main body 1 is mounted on the carriage 11 and further an ink cartridge 12 for supplying ink to the head main body 1 is installed, and a suction device provided separately from this assembly in a recording apparatus to be described later. FIG. As shown in FIG. 3, the carriage 11 includes a guide hole 14 which engages with a guide rail by a known means as described later, and reciprocates along the guide rail.
A hollow needle portion 16 protrudes from the side of the carriage 11 opposite to the portion to which the head is attached, and this hollow portion is connected to the ink supply passage 5 provided in the liquid chamber main body 2 of the head main body 1 via a coupler 17 made of an elastic member such as rubber. Communicate with The head body 1 is connected to the carriage 11 via the holder 18 and the coupler 17. Fastening projection 1 provided on carriage 11
9, the holder 18 is positioned.

The ink cartridge 12 is of a known type. A seal 22, a filter 23, a first felt 24, and a hollow case 21 having a hollow projection 20 are provided inside the hollow case 21.
The second felt 25 is attached, and the sheet 26 is attached to the end face of the projection. The hollow projection 20 is filled with ink, the first felt 24 and the second felt 25 are soaked with ink, and a lid 28 having a vent hole 27 is attached to the end face opposite to the projection 20. The pressure of the ink in the protrusion 20 is maintained at a constant pressure slightly lower than the atmospheric pressure according to a known operation principle.

The ink cartridge 12 includes a carriage 11
Is connected to the head main body 1. That is, when the protrusion 20 of the ink cartridge 12 is pushed in such a manner as to abut the needle 16 on the rear surface of the carriage 11,
The needle portion 16 breaks through the sheet 26 and enters the hollow portion of the ink cartridge 12 while pressing the seal 22 provided in the ink cartridge 12.

FIG. 4 is a perspective view showing a recording apparatus equipped with the ink jet head of this embodiment. In the recording apparatus shown in FIG. 4, the carriage 11 is driven by a carriage motor (not shown) via the timing belt 30, and moves to a position facing the suction device 13 along the guide rail 15. In this state, the suction device 13 is moved toward the head main body 1 by a known means. The suction device 13 includes a cap 31 made of an elastic material such as rubber, a vent 32 communicating with an unillustrated atmospheric release valve, and an exhaust hole 33 communicating with a suction pump (not shown).

FIG. 5 is a time chart showing the operation of the related members in the head recovery operation including the defoaming operation. After the cap 31 is advanced and pressed against the nozzle plate 35 having the nozzle holes 34 of the head body 1, the air release valve is closed, and the air in the cap 31 is sucked by the suction pump. When the suction operation starts, the ink cartridge 1
2 passes through the through hole 36, passes through the hollow portion 37 of the needle portion 16, passes through the ink supply path 5, and passes through the common liquid chamber 4 and the pressure chamber 3.
And fill them.

Here, in addition to the operation of the suction pump, a vibration drive circuit, which will be described later, is operated to apply an ultrasonic alternating voltage to the vibration piezoelectric element 9 to ultrasonically vibrate the outer wall 38 of the common liquid chamber 4. . As a result, the pressure of the ink in the common liquid chamber 4 alternately fluctuates at the ultrasonic frequency and acts on the relatively large air bubbles 40 attached to the inner wall surface 39 to be separated from the wall surface 39. The detached bubble 40 vigorously flows through a portion serving as an ink flow path. Next, the ends of the bubbles are the common liquid chamber 4 and the pressure chamber 3
Between the narrow passages 41. When passing through this passage 41, the ratio of the diameter to the length of the bubble becomes unstable and breaks into a number of small bubbles. The divided small bubbles move to the pressure chamber 3 together with the sucked ink, and are further discharged to the outside through the nozzle holes 34. At this time, the bubbles 40 that are separated from the inner wall surface 39 of the common liquid chamber 4 are also discharged to the outside similarly along with the flow of ink.

Therefore, if the suction pump and the vibration drive circuit are operated simultaneously for a necessary time, the common liquid chamber 4 and the pressure chamber 3 can be filled with ink without bubbles. it can. Here, the required operation time is shorter in the case of a simple head recovery operation described later than in the case of the start-up operation when the ink cartridge 12 is exchanged as described above. It is desirable to operate the suction pump and the vibration drive circuit simultaneously for a time sufficiently longer than the required operation time.

After the suction (filling) of the ink is completed, the air release valve is opened as shown in FIG. 5 and the pressure in the cap 31 is set to the atmospheric pressure. The air in the cap is sucked through 33.
That is, a release suction operation is performed. Thereby, the outside air is released to the atmosphere, the vent hole 32, the cap 31, the exhaust hole 33.
Through the suction pump. As a result of this, cap 31
The airflow flows through. By this air flow, most of the ink accumulated in the cap 31 due to the suction of the ink is pushed out and removed toward the suction pump. However, ink still remains on the portion where the air current does not flow much, that is, on the surface of the nozzle plate 35 or inside the tip of the cap.

Next, the suction device 13 is retracted by a known means, so that the cap 31 is retracted and separated from the nozzle plate 35, and a carriage motor (not shown) is rotated to drive the carriage 11 via the timing belt 30 shown in FIG. Is moved along the guide rail 15 in the right-hand direction in the figure, and the nozzle plate 35 of the head main body 1 is moved from the position facing the cap 31 of the suction device 13 to the cleaning device 42.
And moves to a position where it comes into contact with and slides on the flexible blade 43. Next, the carriage motor is rotated in reverse to move the carriage 11
Is moved in the left-hand direction of the drawing to slide the nozzle plate 35 into contact with the blade 43, and further repeats the forward and reverse rotations of the carriage motor to reciprocate the carriage 11 to slide the nozzle plate 35 and the blade 43. Is repeated, the nozzle plate 35 is returned to the position facing the cap 31 again.
Such a so-called wiping operation allows the nozzle plate 35
Wipe off the ink remaining on the surface of the.

Next, the nozzle plate 3
5, the pressure chamber piezoelectric element 8 shown in FIG. 1 of the head body 1 is driven to pressurize all the pressure chambers 3 to discharge ink from all the nozzle holes 34, so that the so-called idle discharge is performed. Do. By this empty discharge, old ink with deteriorated properties such as viscosity remaining in the pressure chamber can be completely removed, replaced with new ink, and the wet state of the outlet of the nozzle hole 34 can be made uniform. In addition, the meniscus can be adjusted while keeping the boundary conditions constant.
After the completion of the idle discharge, the suction device 13 is operated as it is, so-called idle suction is performed, and the ink accumulated in the cap 31 due to the idle discharge is removed. However, ink still remains inside the tip of the cap 31 as described above.

Next, the cap 31 is pressed against the nozzle plate 35 and then separated to transfer the ink remaining inside the tip of the cap 31 to the nozzle plate 35. Next, when printing is performed continuously after wiping the ink transferred to the nozzle plate 35 by the same wiping operation as described above, the carriage 11 is moved to a position facing the recording paper 44 in the recording apparatus shown in FIG. Then, ink is ejected from the nozzle holes 34 of the head main body 11 mounted on the carriage 11, and recording is performed on the recording paper 44 while moving the carriage 11 right and left in the printing area. The recording paper 43 is sent onto a platen 47 by a feed roller 45 and a discharge roller 46. When the recording operation is not performed, after wiping, the carriage 11 is moved to the left, the nozzle plate 35 is returned to the position facing the cap 31, and the cap 31 is pressed against the nozzle plate 35 after closing the air release valve. Maintain the state and prevent the ink from drying and mixing of dust.

As shown in FIG. 5 and described above, the defoaming operation of the head body 1 in this embodiment is performed in synchronization with the ink suction (filling) process as a part of the recovery operation. The recovery operation of the head main body 1 in the present embodiment is performed when the ink cartridge 12 is attached to the carriage 11 for the first time, when the ink cartridge 12 is replaced, when the recording apparatus is started, or during a printing operation, for example, at a line feed or a page feed. . In these recovery operations, the defoaming operation is performed in synchronization with the ink suction process.

The driving of the pressure chamber piezoelectric element 8 for recording is performed by a known method. A part or all of the plurality of pressure chamber piezoelectric elements 8 are selected based on the print data, and the selected pressure chamber piezoelectric elements 8 are simultaneously driven by applying or releasing a voltage, and the outer wall of the corresponding pressure chamber 3 is driven. Is deformed, and ink is ejected by pressurization. By driving the piezoelectric element 8 for the pressure chamber in the opposite direction by applying or releasing a voltage to the pressure chamber 3 after the discharge, the outer wall of the pressure chamber 1 is deformed in the opposite direction, and the common liquid chamber is depressurized. Ink suction from 4 and filling. Here, the pressure chamber piezoelectric element 8 is d3
Operate in three modes. That is, application and release of the voltage expands and contracts in the stacking direction, and deforms the outer wall of the pressure chamber 3 in the vertical direction.

The vibrating piezoelectric element 7 joined to the outer wall of the common liquid chamber 4 operates in the d31 mode, expands and contracts in the length direction by applying a driving voltage, and deforms the outer wall 38 of the common liquid chamber 4 in the bending mode. . That is, when a voltage is applied between the electrodes of the vibrating piezoelectric element 9 and the length of the element is extended, the outer wall 38 is deformed downward and the volume of the common liquid chamber 4 is increased. When a voltage is applied in a direction opposite to this, the length of the correcting piezoelectric element 4 is reduced, and the outer wall 38 is deformed to protrude upward, and the volume of the common liquid chamber 4 is reduced.

FIG. 6 is a diagram showing a configuration of a vibration drive circuit for driving the vibration piezoelectric element 7. This circuit constitutes an oscillation circuit as a whole. One electrode 51 of the vibrating piezoelectric element 9 is connected to the collector of the npn bipolar transistor 50 via the capacitor C2, and the other electrode 5 is connected to the base.
2 is connected. The collector is separately connected to the power line Hv on the high potential side of the power supply via the impedance Z1 and the switch means S.
Connect to The base is connected to the low potential side of the power supply via the capacitor C1, and the base is further connected to the bias resistor R1.
And R2 are connected to the switch means S and the low potential side of the power supply, respectively. Emitter with impedance Z2
To the low potential side of the power supply.

Next, the operation of the vibration drive circuit will be described. Initially, the switch means S is in the OFF state, the electrodes 51 and 52 of the vibration piezoelectric element 9 are both at the low potential side of the power supply, and no voltage is applied to the vibration piezoelectric element 9. In state. When the switch means S is turned on,
First, a current flows through the bias circuits R1 and R2, and the voltage V52 of the electrode 52 becomes equal to the bias voltage VB0 obtained by dividing the power supply voltage V by the resistance ratio, and this voltage is applied to the base to flow a base current, which is amplified. In this manner, the collector current flows through Z1 to determine the collector voltage VC0, and a voltage V51 determined by the collector voltage is applied to the electrode 51. At this time, V52 is a base voltage, and V51 is an intermediate voltage between the collector voltage and the base voltage. Therefore, a new voltage rises between the electrodes, and a mechanical pulse is applied to the piezoelectric element 9 for excitation to produce a small amplitude Δs Start mechanical vibration of Due to this mechanical vibration, the electrode 52 of the vibrating piezoelectric element 7
An AC-induced piezoelectric having an amplitude Δe is generated between the electrode 51 and the electrode 51. This induced voltage is superimposed on the bias voltage VB0 and input to the base.

As a result, the collector voltage is obtained by superimposing an AC voltage having an amplitude of βΔe and a phase opposite to that of the induced voltage, with the above-mentioned VC0 as a bias. Where β is the voltage amplification, which is significantly greater than 1. The AC component of the collector voltage is transmitted to the electrode 51 and vibrates the vibrating piezoelectric element 9 to generate an induced voltage having an amplitude of γβΔe, a phase opposite to the collector voltage, and the same phase as the induced voltage. As a result, the voltage amplitude of the AC component of the electrode 52 becomes βγ times larger than that at the beginning and returns. Here, γ is a voltage transfer coefficient of the piezoelectric element 9 for excitation on the electric circuit, and is smaller than 1. But γ
Is not a single piezoelectric element 9 for vibration, but is determined as the overall characteristics of the electromechanical converter including the mechanical characteristics of the common liquid chamber. If βγ is greater than 1,
Each time the feedback loops, the amplitude of the AC voltage applied to the piezoelectric element 9 for vibration increases, and the oscillator oscillates, and the external wall of the piezoelectric element 9 for vibration and the common liquid chamber 4 coupled thereto become integral with the external wall and ink. It vibrates at a frequency that is the same as or close to the natural frequency of the common liquid chamber 4 that contains it.

At this time, the oscillation amplitude does not increase infinitely, but the oscillation continues at an amplitude where βγ becomes 1 due to the amplitude dependency (nonlinearity) of the voltage amplification β. Even when the voltage transfer coefficient γ of the piezoelectric element 7 for excitation is considerably small, if the amplification means of the excitation drive circuit is a known multi-stage amplification circuit using a plurality of transistors such as a Darlington circuit, β in the linear region can be reduced. And the excitation drive circuit can oscillate by increasing βγ to be larger than 1. The switch means S presses the cap 31 against the nozzle plate 35,
When the air release valve is opened and the suction pump is operating, a control signal is generated by a known means based on a control signal for these operations or an output of a state detection sensor such as a microswitch or a photosensor. A switch means S which keeps the cap 31 pressed against the nozzle plate 35, opens the air release valve, and sets the control signal for these operations when the suction pump is in operation. Alternatively, a control signal is generated by a known means based on the output of a state detection sensor such as a microswitch or a photosensor and turned on, and otherwise turned off.

Next, a second embodiment of the present invention will be described. FIG. 7 is a diagram showing the configuration of the vibration drive circuit in this embodiment. This embodiment is the same as the first embodiment except for the vibration drive circuit. In FIG. 7, Tr1, Tr3, Tr
4, Tr6 is an npn bipolar transistor;
r2 and Tr5 are pnp bipolar transistors.
The emitters of pnp bipolar transistors Tr2 and Tr5 are connected to the high potential side of the power supply, the bases are connected to the high potential side of the power supply via resistors R2 and R4, respectively, and npn bipolar transistors Tr1 and Tr4 are connected via resistors R1 and R3. Connect to the collector.
The npn bipolar transistors Tr1 and Tr4 are respectively connected to the low potential side of the power supply. The collectors of the pnp bipolar transistors Tr2 and Tr5 are respectively n
The collectors of the pn bipolar transistors Tr3 and Tr6 are connected, and the emitters of the npn bipolar transistors Tr3 and Tr6 are respectively connected to the low potential side of the power supply.

The one electrode 51 of the piezoelectric element for vibration 7 is pn
The collector is connected to the collectors of the p bipolar transistor Tr2 and the npn bipolar transistor Tr3, and the other electrode 52 of the vibrating piezoelectric element 9 is connected to the collectors of the pnp bipolar transistor Tr5 and the npn bipolar transistor Tr6. 61 is a first enable signal p1
Is connected to the delay circuit 62 and is connected to the base of the npn bipolar transistor Tr1 and one input terminal of the first OR gate 65 via a branch line.

The output line 63 of the delay circuit 62 for outputting the second enable signal p2 is connected to the base of the npn bipolar transistor Tr4 and one input terminal of the second OR gate 66. The discharge signal line 64 that outputs the discharge control signal signal p3 is connected to the other input terminals of the first OR gate 65 and the second OR gate 66. The output lines of the first OR gate 65 and the second OR gate 66 are connected to the base of the npn bipolar transistor Tr6 and the base of the npn bipolar transistor Tr3, respectively. S1 and S2 are switch means provided in the middle of the enable signal line 61 and the discharge signal line 64, respectively.

The operation of the above vibration drive circuit will be described. This vibration driving circuit is not an oscillation circuit, but applies a driving voltage pulse having a predetermined frequency to the vibration piezoelectric element 9 based on a predetermined control signal. The outer wall is forcibly driven at the predetermined frequency. FIG. 8 is a time chart showing the operation of the circuit. First, the switch unit S1 is initially OFF and the switch unit S2 is ON. However, when the ink suction operation in the recovery operation similar to that described in the first embodiment starts, that is, the cap 31 is removed from the nozzle plate 3
5, when the atmosphere release valve is opened and the suction pump is in operation, the control signal for these operations or the output of a state detection sensor such as a microswitch or a photosensor is used by known means. A control signal is generated to turn off the switch means S2 and turn on the switch means S1 with a slight delay. When the ink suction operation is completed, first, the switch means S1 is turned off by the same means.
F, and the switch means S2 is turned on with a slight delay.

As described above, when the device starts up, the switch means S1 is OFF and the switch means S2 is ON, so that the enable signal p1 on the enable signal line 61 is L and the output signal 63 of the delay circuit 62 is on. The second enable signal p2 is L, the control voltage p on the discharge control line 64
3 is H. As a result, the npn bipolar transistors Tr3 and Tr6 are turned on, while the npn bipolar transistors Tr1 and Tr4 are turned off,
The base voltages of the pnp bipolar transistors Tr2 and Tr5 are increased to turn them off. As a result, the vibrating piezoelectric element 7 is discharged, and the electrodes 50 and 51 are both at the level on the lower potential side of the power supply.
Is in the zero state.

Next, the switch means S2 is turned off from ON, and the switch means S1 is turned off slightly and the switch means S1 is turned off for
First, the control voltage p3 on the discharge control line 64 becomes L, and the npn bipolar transistor Tr
3. After turning Tr6 off once, enable signal line 6
1, the first enable signal p1 becomes H, and the npn bipolar transistors Tr1, Tr6 are turned on from OFF.
And At this time, a current flows through the resistors R1 and R2, and pn
The base potential of the p-type bipolar transistor Tr2 is lowered and changed from OFF to ON. At this time, the second enable signal p2 on the output line 63 of the delay circuit 62 is in the L state, and the npn bipolar transistors Tr3, Tr4, p
The np bipolar transistor Tr5 is still OFF. After the control voltage p3 has once become L, it continues to be L while the circuit is operating.

As a result, the pnp bipolar transistor Tr2, the vibrating piezoelectric element 7, the npn
A charging route is formed to reach the low potential side of the power supply through the bipolar transistor Tr6, and the vibration piezoelectric element 7 is charged. One electrode 51 of the vibration piezoelectric element 7 is connected to the high potential side voltage of the power supply. The other electrode 52 has a voltage on the lower potential side of the power supply, and a voltage V equal to the power supply voltage is applied to the vibration piezoelectric element 9 in the direction from the electrode 51 to the electrode 52, and the vibration piezoelectric element 9 is expanded and Apply force. Here, after turning off the npn bipolar transistor Tr3, pnp
Since the bipolar transistor Tr2 is turned on, O
Through current at the time of switching between N and OFF can be prevented.

As shown in FIG. 8, the enable signal line 61
The upper first enable signal p1 has a pulse width T1 having a period T.
Is a continuous pulse equal to or less than 1/2 of. The second enable signal p2 on the output line 63 of the delay circuit 62 has the same pulse width T1 and period T as the first enable signal, but rises when p1 is in the L state later than p1, and p2
It falls before 1 goes high. Accordingly, the period T2 from the fall of p1 to the rise of p2 and T2 and p2
Both p1 and p2 are L during a period T3 from the fall to the rise of p1. When the first enable signal p1 on the enable signal line 61 falls from H to L and the second enable signal p2 on the output line 63 of the delay circuit 62 is also in L state (period T2), all transistors are turned on. Is turned off and the piezoelectric element 9 for vibration
Is in a state where the voltage V is applied in the forward direction.

Next, when the second enable signal p2 rises to H while the first enable signal p1 is at L, n
pn bipolar transistors Tr3, Tr4 and pn
The p-type bipolar transistor Tr5 changes from OFF to ON, and the other transistors are still OFF. This forms a charging route from the high potential side of the power supply to the low potential side of the power supply via the pnp bipolar transistor Tr5, the vibrating piezoelectric element 7, and the npn bipolar transistor Tr3. Charging is performed,
One electrode 51 of the vibrating piezoelectric element 9 has a voltage on the low potential side of the power supply, and the other electrode 52 has a voltage on the high potential side of the power supply.
A voltage V equal to the power supply voltage is applied to the piezoelectric element 9 for excitation in the direction from the electrode 52 to the electrode 51, and when the direction from the electrode 51 to 52 is positive, a reverse voltage of -V is applied. A force in a direction to shorten the piezoelectric element 9 is applied. The reason why all the transistors are temporarily turned off before switching the transistors from OFF to ON is to prevent a through current.

Next, when the first enable signal p1 is at the L level and the second enable signal p2 is at the L level (period T3), all the transistors are turned off.
The state becomes the FF, and the state where the above-described reverse voltage −V is applied to the vibration piezoelectric element 9 is maintained. Next, when the first enable signal p1 rises to H while the second enable signal p2 is L, as described above, p is applied from the high potential side of the power supply.
A charging route is formed through the np bipolar transistor Tr2, the vibrating piezoelectric element 7, and the npn bipolar transistor Tr6 to the lower potential side of the power supply, and the vibrating piezoelectric element 9 is formed.
Is performed, a forward voltage V is applied to the piezoelectric element 9 for excitation, and the piezoelectric element 7 for excitation is expanded to exert a force in the direction. In the same manner, the vibrating piezoelectric element 9
A forward voltage V and a reverse voltage −V are applied to the piezoelectric element 9 to apply a periodic expansion and contraction force to the piezoelectric element 9 for vibration, and the outer wall of the common liquid chamber 4 is cycled through the piezoelectric element 9 for vibration at a period T. Vibrate in bending mode. The frequency f of the vibration is 1 / T, but is preferably an ultrasonic frequency.

Next, although not shown, it is also possible to form the piezoelectric element for vibration 7 in a laminated structure and drive it in the d33 mode. For example, the base 7 shown in FIG.
The vibration piezoelectric element 9 is formed in a laminated structure at a position facing the upper common liquid chamber 4 and joined, and the upper surface thereof is joined to the outer wall of the common liquid chamber 4. The electrode of the piezoelectric element 9 for excitation is F
It is connected to the lead wire of the PC 37 and is electrically connected to the vibration drive circuit. The vibrating piezoelectric element 9 is d as in the case of the pressure chamber piezoelectric element 5.
It behaves in 33 mode, expands and contracts in the stacking direction, and
Vibrates the outer wall perpendicular to the plane. According to this example,
The vibrating force of the vibrating piezoelectric element 97 is increased by the effect of the lamination of the piezoelectric elements, the amplitude of the vibration of the outer wall of the common liquid chamber 4 is increased, and the defoaming effect is more easily enhanced.

[0043]

As described above, according to the present invention,
Without any special suction device in the ink jet head and without causing ink leakage from the nozzle holes, remove and discharge the air bubbles adhering to the common liquid chamber without fail, and perform the ink ejection operation normally. This can be achieved by using a small-sized and simple inkjet head advantageous for high-speed printing.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of an ink jet head main body according to the present invention.

FIG. 2 is a cross-sectional view illustrating a structure of an inkjet head body according to the present invention.

FIG. 3 is a diagram showing the structure of an inkjet head body, a carriage, an assembly of ink cartridges, and a separate suction device according to the present invention.

FIG. 4 is a diagram showing a recording apparatus equipped with an inkjet head according to the present invention.

FIG. 5 is a time chart showing a recovery operation of the inkjet head according to the present invention.

FIG. 6 is a diagram showing a configuration of a vibration drive circuit for defoaming ink in an ink jet head according to the present invention.

FIG. 7 is a diagram showing a configuration of a vibration drive circuit for defoaming ink in an ink jet head according to the present invention.

FIG. 8 is a time chart showing the operation of the structure of a vibration drive circuit for defoaming ink in an ink jet head according to the present invention.

FIG. 9 is a view showing a structure of a conventional inkjet head main body.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Head main body 2 Liquid chamber main body 3 Pressure chamber 4 Common liquid chamber 5 Ink supply path 6 Diaphragm 7 Base 8 Piezoelectric element for pressure chamber 9 Piezoelectric element for vibration 10 FPC 11 Carriage 12 Cartridge 13 Suction device 14 Guide hole 15 Guide rail Reference Signs List 16 needle part 17 coupler 18 holder 19 fastening protrusion 20 protrusion 21 hollow case 22 seal 23 through hole 24 first felt 25 second felt 26 sheet 27 vent hole 28 lid 30 timing belt 31 suction device 32 vent hole 33 exhaust Hole 34 Nozzle hole 35 Nozzle plate 36 Through hole 37 Hollow part 38 Outer wall 39 Inner wall surface 40 Bubble 41 Narrow passage 42 Recovery device 43 Blade 44 Recording paper 45 Paper feed roller 46 Paper discharge roller 47 Platen 50 npn bipolar transistor 51, 52 Electrode 61 Rice Bull signal line 62 Delay circuit 63 Output line 64 Discharge signal line 65 First OR gate 66 Second OR gate

Claims (4)

[Claims] 1. A pressure chamber having a plurality of pressure chambers and a common liquid chamber communicating with the pressure chambers. The outer walls of the pressure chambers are deformed and pressurized by piezoelectric driving, and ink is ejected from nozzle holes communicating with the pressure chambers. An ink jet head for performing printing, wherein a vibrating means for defoaming ink is provided on an outer wall of the common liquid chamber. 2. A pressure chamber having a plurality of pressure chambers and a common liquid chamber communicating with the pressure chambers, wherein the outer walls of the pressure chambers are deformed and pressurized by piezoelectric driving, and ink is ejected from nozzle holes communicating with the pressure chambers. The vibrating means of the ink jet head, in which the vibrating means for defoaming the ink is attached to the outer wall of the common liquid chamber of the ink jet head for performing printing, while the outer wall is vibrated, the suction means separate from the ink jet. A bubble in the ink together with the ink is sucked out of the nozzle hole, and the ink is defoamed. 3. The ink jet head according to claim 1, wherein the outer walls of the pressure chamber and the common liquid chamber are constituted by a common diaphragm, and a piezoelectric member is joined to the outer wall of the common liquid chamber as a vibration means. 4. The method for defoaming ink of an ink-jet head according to claim 2, wherein the defoaming of the ink according to claim 2 is performed using a recovery device for the ink-jet head as suction means.