JP2001171109A - Ink jet head and its driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the circuit of a driving section by controlling one wall with a set of two and a half switches as compared with a conventional set of three switches. SOLUTION: An ink pressurizing chamber 6 is defined by left and right walls comprising a layer of upper and lower intermediate piezoelectrics 2, 4. An upper common electrode 1, the upper intermediate piezoelectric 2, an intermediate electrode 3, the lower intermediate piezoelectric 4, and a lower common electrode 5 are laid in this order. When +V/2 volt is applied to the upper common electrode 1 and the lower common electrode 5 and +V volt and 0 volt are applied alternately to terminals 7A, 7B, ink is sucked and ejected to an ink pressurizing chamber 6. In other cases, the terminals 7A, 7B are short- circuited through a switch SW5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ink jet head and a driving method thereof.

[0002]

2. Description of the Related Art An ink jet printer prints on a medium such as paper by ejecting ink contained in an ink pressurized chamber by electric pulses. As one of the methods of ejecting ink, there is a method of surrounding an ink pressurizing chamber with a piezoelectric body and applying an electric field in a certain direction to the piezoelectric body to generate distortion. An ink jet head employing this method is provided with a number of electrodes for applying an electric field to the piezoelectric body and a drive circuit for applying a voltage to each electrode in a predetermined sequence.

The driving circuit is provided with a switch for turning on and off a power supply for applying a voltage to each electrode. By driving these switches in a predetermined sequence, an operation of sucking ink into the ink pressurizing chamber and discharging the ink is controlled.

[0004]

However, the above-mentioned prior art has the following problems to be solved. In an ink jet head using a piezoelectric material as described above, conventionally, in order to alternately apply + V volt, −V volt, and 0 volt to a control electrode, each ink separation chamber is separated by one wall. And a driving circuit including a set of three switches. However, a large number of ink pressurizing chambers are provided in the ink jet head, and when a set of three switches is connected to electrodes for driving these walls, the circuit scale of the drive circuit as a whole becomes large,
There was a problem that the cost was high.

[0005]

The present invention employs the following structure to solve the above problems. <Structure 1> An upper common electrode, an upper intermediate piezoelectric body group, an intermediate electrode group, a lower intermediate piezoelectric body group, and a lower common electrode are sequentially laminated, and the upper intermediate piezoelectric body sandwiching the intermediate electrode, respectively. A pair of walls partitioning the ink pressurizing chamber group is formed by the body and the lower intermediate piezoelectric body, and all the upper intermediate piezoelectric body and the lower intermediate piezoelectric body are connected from the upper common electrode or the lower common electrode to the intermediate electrode. The direction of the polarization axis is set so that the shear mode deformation occurs when an electric field oriented in the direction toward or in the opposite direction is formed, and a predetermined bias voltage of the same potential is supplied to the upper common electrode and the lower common electrode. ,
A drive voltage higher than the bias voltage is supplied to an intermediate electrode of one of the pair of walls, and a drive voltage lower than the bias voltage is applied to an intermediate electrode of the other wall of the pair of walls. And when the wall is driven and the wall is not driven, the intermediate electrodes of the pair of walls are electrically short-circuited to each other.

<Structure 2> The ink jet head according to Structure 1, wherein adjacent ink pressurizing chambers share a wall therebetween.

<Structure 3> In the ink-jet head according to Structure 1, the adjacent ink pressurizing chambers are arranged with a space therebetween, and the ink pressurizing chambers are sandwiched by independent walls. Inkjet head.

<Structure 4> An upper common electrode, an upper intermediate piezoelectric body group, an intermediate electrode group, a lower intermediate piezoelectric body group, and a lower common electrode are sequentially laminated, and each of the above-mentioned intermediate electrodes is sandwiched therebetween. The upper intermediate piezoelectric body and the lower intermediate piezoelectric body form a pair of walls that partition the ink pressurizing chamber group, and all of the upper intermediate piezoelectric body and the lower intermediate piezoelectric body are separated from the upper common electrode or the lower common electrode by The direction of the polarization axis is set so that an electric field directed in the direction toward the intermediate electrode or in the opposite direction is formed so as to undergo shear mode deformation. A predetermined bias voltage of the same potential is supplied, starting from a state in which both the intermediate electrodes of the pair of walls are electrically short-circuited, to the intermediate electrode of one of the pair of walls,
A drive voltage higher than the bias voltage is supplied, and a drive voltage lower than the bias voltage is supplied to the intermediate electrode on the other of the pair of walls, and ink is sucked into the ink pressurizing chamber. At the next timing, a drive voltage lower than the bias voltage is supplied to the intermediate electrode of one of the pair of walls, and the bias voltage is applied to the intermediate electrode of the other of the pair of walls. A method for driving an ink jet head, comprising supplying a drive voltage higher than a voltage to eject ink from the ink pressurizing chamber, and then electrically short-circuiting both intermediate electrodes of the pair of walls.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below using specific examples. <Example 1> FIGS. 1A and 1B show an example of an ink-jet head driving unit according to the present invention. FIG. 1A is a sectional view of a main part of the ink-jet head, and FIG.
In this figure, only the main elements around one ink pressurizing chamber 6 constituting the ink jet head are shown in cross section.

As shown in the figure, the upper common electrode 1 is attached to an upper top plate 27, and the lower common electrode 5 is attached to a lower top plate 28. The upper common electrode 1, the upper intermediate piezoelectric body 2, the intermediate electrode 3, the lower intermediate piezoelectric body 4, and the lower common electrode 5 are stacked in this order to form one wall. Numerous walls are provided between the upper common electrode 1 and the lower common electrode 5, and an ink pressurizing chamber 6 is formed between them.

The upper intermediate piezoelectric body 2 has electrodes 1-2 and 3-2 attached to upper and lower surfaces thereof. Further, the lower intermediate piezoelectric body 4 has electrodes 3-3 and 5-2 attached to the upper and lower surfaces thereof. Then, the upper common electrode 1 and the electrode 1-2
Are bonded to each other by the conductive adhesive 1-1. The electrode 3-2 and the electrode 3-3 are adhered by the conductive adhesive 3-1. The electrode 5-2 and the lower common electrode 5 are bonded by a conductive adhesive 5-1.

The electrode 3-2 and the electrode 3-3 are adhered by the conductive adhesive 3-1 and thus function as an electrically equivalent electrode. Therefore, these are collectively referred to as an intermediate electrode 3 and the following description will be continued. The terminal 7A is connected to the intermediate electrode 3 on the right wall in the figure. A terminal 7B is connected to the intermediate electrode 3 on the left wall in the figure.
The upper common electrode 1 and the lower common electrode 5 are short-circuited,
Here, terminal 7C is connected. The upper intermediate piezoelectric body 2 and the lower intermediate piezoelectric body 4 are both piezoelectric bodies polarized in the direction of arrow P in the figure.

The drive section shown in (b) is a switch control section 1
1 and switches SW1, SW2, SW3, SW4, SW
5, SW6, SW7, and a power supply 12 of + V volt. Two switches SW1 and SW2
Are electrically connected to the terminal 7A shown in FIG. Also, 2
Outputs of a set of switches SW3 and SW4 are electrically connected to a terminal 7B shown in FIG. As described above, in the present invention, two switches are respectively connected to the intermediate electrodes 3 on each wall, and drive control is performed. In the example of this figure, since two walls are driven, a total of 2 × 2 = 4
Although three switches are shown, the number of switches is twice as many as the number of walls.

Note that a switch SW5 is inserted between the terminals 7A and 7B. The switches SW6 and SW7 are inserted between adjacent similar terminals. Thus, when the switch SW5 is turned on, the terminals 7A and 7B are short-circuited, and when the switch SW5 is turned off, the terminals 7A and 7B are turned off.
B is connected so as to be insulated. The terminal 7C is connected so that a constant voltage of + V / 2 volts is applied.

The output of the power supply 12 shown in FIG.
1, SW3. Therefore, the switch S
When W1 is turned on, the potential of the terminal 7A becomes + V volt, and when the switch SW3 is turned on, the potential of the terminal 7B becomes + V.
V volts. Also, the switch SW2 and the switch SW
4 is held at the ground potential. Therefore, when the switch SW2 is turned on, the potential of the terminal 7A becomes 0 volt. When the switch SW4 is turned on, the potential of the terminal 7B becomes 0 volt. Further, for example, when both the switches SW1 and SW2 are opened, the terminal 7A is kept in a high impedance state.

The switch SW1 and the switch SW2 operate exclusively so that, in principle, only one of them is turned on. In some cases, both switches SW1 and SW2 are turned off at the same time. In addition, the switch SW3 and the switch SW4 operate mutually exclusively so that, in principle, only one of them is turned on. In some cases, both switches SW3 and SW4 are turned off at the same time. Switch control unit 1
1 controls these switches SW1 to SW4 and SW5 at a timing to be described later.

The upper part of each member shown in FIG.
The lower part is named in consideration of the apparent position when the posture is as shown in the figure, and the upper part need not necessarily be arranged at the upper part. It is simply a name given for convenience in order to clarify the positional relationship of each member.

FIG. 2 is a perspective view of a general ink jet head. The illustrated ink jet head body 20 is provided with an ink suction port 29 at an upper portion thereof, from which ink is supplied through an ink tank (not shown).
The orifices 22 are arranged at the front end by the number of ink pressurizing chambers. From the rear end, an electrode 15 for driving these
And a signal cable (not shown) is connected thereto. A conductor 17 for short-circuiting between the electrodes is attached to the side surface, and a sealing material 18 for sealing the ink pressurizing chamber is attached to the rear portion.

FIG. 3 is a sectional view of a print head JJ of a comparative example. This figure is a longitudinal sectional view of the ink jet head along the line JJ shown in FIG. An orifice 22 is arranged at the left end shown in the figure. Further, an ink pressurizing chamber 16 is arranged at the center. The upper and lower surfaces of the ink pressurizing chamber 16 are sandwiched between the upper top plate 23 and the lower top plate 21. Further, the electrodes 2 are used to drive the ink pressurizing chamber 16.
4, 25 are provided. The extended portion of the electrode 25 becomes the electrode 15 and is electrically connected to an external signal cable.

FIG. 4 shows a connection diagram of a driving section of a comparative example.
A driving unit as shown in FIG. 2 is connected to an ink jet head having a conventional structure as shown in FIGS. The three switches SW1, SW2, and SW3 shown in the figure are operated by the switch control unit 11 so that one of them is exclusively turned on. These switches also have a power supply 1
2A and 12B are electrically connected.

The outputs of the switches SW1, SW2, and SW3 are collectively connected to a terminal OUT. This terminal OUT
Are electrically connected to the electrode 15 shown in FIG. Further, a terminal E for grounding is connected to the electrode 24. Switch SW
When 1 is turned on, a voltage of + V volt is output from the terminal OUT. When the switch SW2 is turned on, the terminal O
A voltage of 0 volt is output from the UT. When the switch SW3 is turned on, a voltage of -V volt is output from the terminal OUT.

FIG. 5 is a timing chart showing the operation of the driving section according to the comparative example. The driving section described above operates at the timing shown in FIG. Switch SW1, SW
2 and SW3 are ON / OFF controlled in a fixed pattern as shown in FIG. In the following figures, all the switches are turned on when the signal level is high, and turned off when the signal level is low. (A) to (c) show the operation timings of the switches SW1, SW2, and SW3, respectively, and (d) shows the output voltage level of the terminal OUT where the outputs of the switches are combined. The output voltage of (d) is + V volt at the high level, 0 V at the intermediate level, and −V volt at the low level.

As shown in FIG. 5, when the driving of the ink jet head is started, each switch operates exclusively so that one of the switches is turned on and the other switches are turned off. As a result, as shown in FIG.
Signals are output from the terminal OUT in the order of + V volt, −V volt, 0 volt, −V volt, + V volt, and 0 volt. When the output of the terminal OUT changes to + V volts, −V volts, and 0 volts, the wall of the ink chamber is deformed by one cycle to eject one drop of ink.

FIG. 6 is a diagram illustrating the operation of an ink jet head according to a comparative example. (A) and (b) of the figure each show a part of a cross section along the line KK of the inkjet head of the comparative example shown in FIG. 3. Here, the ink pressurizing chambers are indicated as V1, V2, and V3. They are,
It is surrounded by the upper top plate 23, the intermediate piezoelectric body 26, and the lower top plate 21. Intermediate piezoelectric body 26 and lower top plate 2
1 is polarized in the direction of arrow P in the figure. Upper top plate 23
The electrode 24 is provided between the first piezoelectric element 26 and the intermediate piezoelectric element 26.
Further, intermediate electrodes P1 to P4 are provided between the intermediate piezoelectric body 26 and the lower top plate 21.

The intermediate electrodes P1 to P4 are electrically separated from each other, and are configured to apply a predetermined electric field to the corresponding intermediate piezoelectric body 26 sandwiched between the electrodes 24. The electrode 24 is connected to the terminal E shown in FIG. 4 and is kept at the ground potential. Here, it is assumed that -V volt is applied to the intermediate electrode P2 and + V volt is applied to the intermediate electrode P3, for example. In this case, an electric field E is applied in the direction of the arrow shown in FIG.

The direction of the polarization axis P of the intermediate piezoelectric body 26 and the lower top plate 21 is set so that the intermediate piezoelectric body 26 and the lower top plate 21 undergo shear mode deformation when an electric field E is applied. as a result,
As shown by the broken line in the figure, the wall sandwiching the ink pressurizing chamber V2 is deformed. As a result, the volume of the ink pressurizing chamber V2 increases, and ink is sucked from an ink tank (not shown).

At the next timing, a voltage of + V volt is applied to the intermediate electrode P2 and a voltage of -V volt is applied to the intermediate electrode P3, as shown in FIG. That is, the voltage applied to the intermediate electrode P2 and the intermediate electrode P3 is switched by switching the switch shown in FIG. Thereby, the deformation direction of the wall sandwiching the ink pressurizing chamber V2 is reversed, and the volume of the ink pressurizing chamber V2 is reduced as shown by the broken line in the figure. Thus, the ink inside the ink pressurizing chamber V2 is ejected from the orifice 22.

When the ink pressurizing chamber V2 is not driven, a voltage of 0 volt is applied to both the intermediate electrodes P2 and P3 so that the wall is vertical. For this reason, conventionally, a mechanism for applying voltages of + V volt, −V volt, and 0 volt is required, and a set of three switches is connected to each intermediate electrode.

FIG. 7 shows a timing chart of the ink jet head of the comparative example. (A) shown in the figure is an intermediate electrode P1, (c) is an intermediate electrode P2, (e) is an intermediate electrode P3,
(G) shows the lapse of time of the voltage applied to the intermediate electrode P4. This voltage is the same as the pattern already described with reference to FIG. (B) shows the change in volume of the ink pressurizing chamber V1, (d) shows the change in volume of the ink pressurizing chamber V2, and (f) shows the change in volume of the ink pressurizing chamber V3. This volume change indicates that the volume is larger at the upper side of the figure and smaller at the lower side.

For example, in the case of the ink pressurizing chamber V1 shown in (b), the intermediate electrodes P1 and P2 for driving the walls on both sides thereof are
When a voltage is applied at a timing as shown in the figure, the volume of the ink pressurizing chamber V1 reaches a maximum at a time t1, and then reaches a minimum immediately thereafter. Thus, an operation of sucking and ejecting ink is performed. Thereafter, either one of the walls is driven, but the ink is not ejected because the change in volume of the ink pressurizing chamber is small. Then, at time t4, the walls on both sides are driven again, and the ink pressurizing chamber has the maximum volume, and immediately thereafter, has the minimum volume.

After the times t1, t4, t7, the electrodes P1, P
When a voltage having the same pattern as the voltage applied to the second electrode is applied to each of the other electrodes, as shown in FIG.
2, at time t2, t5, t8, and at time t3, t6, t9, the volume of the ink pressurizing chamber V3 is maximized, respectively.
Immediately after that, an operation of ejecting ink is performed.

FIG. 8 is a diagram for explaining the operation of the ink jet head according to the first embodiment. The specific operation of the inkjet head of the present invention shown in FIG. 8 will be described while comparing with the comparative examples shown in FIGS. 2 to 7. This figure shows a cross section of the ink jet head of the present invention corresponding to the comparative example of FIG. In this ink jet head, the upper top plate 27, the upper common electrode 1, the upper intermediate piezoelectric body 2, the intermediate electrodes 31, 32, 33, and 34, the lower intermediate piezoelectric body 4, the lower common electrode 5, and the lower top plate 28 are arranged in this order. To form ink pressurizing chambers V1, V2, and V3. Although parts having the same configuration are continuous on these left and right sides, illustration is omitted here.

The upper top plate 27, the upper intermediate piezoelectric body 2,
The hatching showing the cross section of the lower intermediate piezoelectric body 4 and the lower top plate 28 is not shown easily, so that the corresponding parts are simply shown. The appearance of this ink jet head is almost the same as the conventional one shown in FIG. 2, and illustration thereof is omitted. FIG.
As described above, in the case of the present invention, a pair of switches of the drive unit is electrically connected to each intermediate electrode 3 respectively.

A bias voltage of + V / 2 volts of the same potential is applied to the upper common electrode 1 and the lower common electrode 5 as described above. Upper intermediate piezoelectric body 2 and lower intermediate piezoelectric body 4
In both cases, the direction of the polarization axis P is set in the direction of the arrow in the figure so that the shear mode deformation occurs when an electric field is applied in the vertical direction in the figure.

Here, consider the case where the ink pressurizing chamber V2 shown in the figure is driven. First, in a normal state that does not work,
An electric field of + V / 2 volts is applied to the upper common electrode 1 and the lower common electrode 5. Therefore, a vertically downward electric field is still applied to the wall formed by the upper common electrode 1 and the lower common electrode 5. However, the wall is not distorted due to the cancellation of the internal stress as described later.

On the other hand, as shown in FIG.
2; 0 volts lower than the bias voltage;
Suppose that a voltage of + V volt higher than the bias voltage is supplied to No. 3. In this case, the upper common electrode 1 and the intermediate electrode 32
And a voltage of + V / 2 volts is applied in this direction, and an electric field E directed downward is applied. Further, a voltage of -V / 2 volts is applied between the intermediate electrode 32 and the lower common electrode 5 in this direction, and an electric field E directed upward is applied. On the other hand, a voltage of -V / 2 volts is applied between the upper common electrode 1 and the intermediate electrode 33 in this direction, and an electric field E directed upward is applied. A voltage of + V / 2 volts is applied between the intermediate electrode 33 and the lower common electrode 5 in this direction, and an electric field E directed downward is applied.

As a result, the upper intermediate piezoelectric body 2 and the lower intermediate piezoelectric body 4 on the left wall of the ink pressurizing chamber V2 shown in FIG.
In the upper intermediate piezoelectric body 2 and the lower intermediate piezoelectric body 4 on the right wall, a shear mode distortion occurs in accordance with the direction of the electric field, and the wall is deformed as shown by a broken line in the figure. As a result, the volume of the ink pressurizing chamber V2 is maximized, and the ink is sucked.

Thereafter, as shown in FIG.
2, a voltage of + V volt is applied, and a voltage of 0 volt is applied to the intermediate electrode 33. At this time, the upper intermediate piezoelectric body 2 and the lower intermediate piezoelectric body 4 on the left wall sandwiching the pressurizing chamber V2 and the upper intermediate piezoelectric body 2 and the lower intermediate piezoelectric body 4 on the right wall are respectively (a). An electric field is applied in a direction completely opposite to the case. As a result, in (b), each wall is deformed in a direction completely opposite to that in (a). The state is also shown by a broken line in (b). Thus, the volume of the ink pressurizing chamber V2 is minimized, and the ink is discharged from the orifice 22.

FIG. 9 is a timing chart of the operation of the driving section according to the first embodiment. In order to perform the above control, the switches SW1, SW2, SW3, SW4, S4 shown in FIG.
W5 is represented by (a), (b), (c), (d),
The ON / OFF operation is performed at the timing shown in FIG.
As a result, a voltage is applied to the terminals 7A and 7B shown in FIGS. 1A, 8A and 8B as shown by thin lines in FIGS. 9F and 9G. 9 (f) and 9 (g) are portions where the corresponding intermediate electrode is held in a high impedance state. In this high impedance state, all switches connected to the corresponding terminal are open. The portion indicated by the thickest line is the portion where the switch SW5 is on.

That is, the terminal 7A remains at the terminal 7B until time t1.
And the same potential state is maintained. Next, the terminal 7A is connected at time t.
The potential is 0 volt between 1 and t2, and is maintained at + V volt between times t2 and t3. During the period from time t3 to t4, the terminal 7B is kept at the same potential as the terminal 7B.
During this period, the high impedance state is maintained. Time t6
From time t7 to the same potential as the terminal 7B,
Between the time t7 and the time t8, the potential is + V volt.
Thereafter, a potential of 0 volt is set between times t8 and t9, and between times t9 and t10, the state is maintained at the same potential as the terminal 7B, and the state returns to the time t1.

The terminal 7B is kept at the same potential as the terminal 7A until time t1. Next, during a period from time t1 to t2, the potential of the terminal 7B is set to a potential of + V volt, and a period from time t2 to time t3
During this time, the potential is set to 0 volt. During the period from time t3 to t4, the terminal 7A is kept at the same potential as that of the terminal 7A. During the period from time t4 to t5, the potential is set to 0 volt. Further, a potential of + V volt is set from time t5 to time t6, and thereafter, from time t6 to time t6.
Until time t7, the terminal is kept at the same potential as the terminal 7A. During a period from time t7 to time t9, the state is kept in a high impedance state. During a period from time t9 to time t10, the terminal 7A is kept at the same potential and returns to the state at time t1.

The switches SW1 and SW shown in FIG.
2 and the operation of the switch SW5 and the potential of the terminal 7A will be described. When the switch SW2 shown in FIG. 1 is turned on, the terminal 7A is held at 0 volt between time t1 and time t2 shown in FIG. Immediately before that, the switch SW5 was turned on, and the terminal 7A and the terminal 7B were held at the same potential. Thereafter, when the switch SW2 is turned off and the switch SW1 is turned on at time t2, a voltage of + V volt is applied to the terminal 7A. At time t3, the switches SW1 and SW2 are turned off and the switch SW5 is turned on, and the terminals 7A and 7B are turned on from time t3 to time t4.
Are maintained at the same potential. Next, at time t4, the switch SW
When the switch 5 is turned off, the terminal 7A is kept in a high impedance state from time t4 to time t6. The operation of such a switch is repeated.

The reason why the terminals 7A and 7B are short-circuited by using the switch SW5 is to equalize the potentials of both terminals. When the potential of each terminal shifts from + V volt or 0 volt to a high impedance state after the end of the ink ejection operation, the potential of the intermediate electrode becomes unstable. However, when both terminals are short-circuited, the pair of walls sandwiching the ink pressurizing chamber both try to be distorted in exactly the same direction at any potential. Accordingly, the volume of the ink pressurizing chamber becomes constant from this point, and the ink is not sucked or ejected. That is, it has a function of forcibly fixing the volume of the ink pressurizing chamber. In this way, the volumes of all the ink pressurizing chambers are forcibly returned to the state equal to the stationary state, and the state immediately shifts to the next driving state. In this case, the response speed of the inkjet head can be improved, and the printing speed can be increased.

FIG. 10 is an explanatory diagram for explaining a specific cross-sectional change of each ink pressurizing chamber when a plurality of ink pressurizing chambers are simultaneously driven. In FIG.
(A) shows a voltage change of the intermediate electrode 31, and (e) shows a voltage change of the intermediate electrode 32. (B) shows a change in volume of the ink pressurizing chamber V1 between the intermediate electrodes 31 and 32. A voltage is applied to each of the intermediate electrodes 31 and 32 as shown by a thin line in FIGS. The part shown by the bold line is the part where the corresponding intermediate electrode is kept in a high impedance state. In this high impedance state, all switches connected to the corresponding terminal are open. The portion indicated by the thickest line is the portion where the switch SW5 is on.

At the timing P1 in the figure, the intermediate electrode 32 becomes + V volt and the intermediate electrode 31 becomes 0 volt, so that the wall sandwiching the ink pressurizing chamber expands to both outer sides as shown in FIG. To be deformed. by this,
The capacity of the ink pressurizing chamber increases. Here, the ink is sucked, and at the next timing P2, the opposite phenomenon occurs.

That is, since the voltage of the intermediate electrode 31 becomes + V volt and the voltage of the intermediate electrode 32 becomes 0 volt, the wall sandwiching the ink pressurizing chamber is deformed so as to contract inward, and the volume of the ink pressurizing chamber rapidly increases. To reduce. Thus, the ink inside the ink pressurizing chamber is ejected. Next timing P3
Then, the intermediate electrode 31 and the intermediate electrode 32 are connected to the switch SW5.
And the volume returns to a quiescent state.

At the next timing, in order to drive the ink pressurizing chamber adjacent to the right side of the ink pressurizing chamber, the wall provided with the intermediate electrode 32 is deformed inward. Further, at the next timing, since the voltage of the intermediate electrode 32 becomes + V volt, the wall on which the intermediate electrode 32 is provided is deformed outward.
However, the ink inside the ink pressurizing chamber is kept as it is because it is designed so that the ink is not ejected in the deformation of one wall at the timing P4 or the timing P5.

At timing P6, the intermediate electrode 31 and the intermediate electrode 32 are short-circuited again, and the volume of the ink pressurizing chamber returns to the stationary state. At the next timing P7, the wall on the side where the intermediate electrode 31 is provided is distorted inward to drive the ink pressurizing chamber adjacent to the left side of the ink pressurizing chamber. At the next timing P8, the wall expands outward. Also in this case, the ink in the ink pressurizing chamber is not ejected. Then, at timing P9, the volume of the ink pressurizing chamber returns to the resting state again, and at the next timing, the state becomes the same as the timing P1, and the operation shifts to the operation of ejecting ink again.

That is, all the walls sandwiching each of the ink pressurizing chambers repeat the operation shown at the timings P1 to P9. Since the ink pressurizing chambers adjacent to each other cannot be driven at the same time, by combining such controls, it is possible to perform control for selecting a target ink pressurizing chamber and ejecting ink. Each of the ink pressurizing chambers is actually driven at an arbitrary timing according to the content of the image data to be printed. Therefore, as shown in FIG. 11, the adjacent ink pressurizing chambers are not necessarily driven at a constant cycle in a fixed order.

FIG. 11 is a timing chart of the ink jet head according to the first embodiment. The voltage applied to the intermediate electrode 31 shown in (a), the voltage applied to the intermediate electrode 32 shown in (c), the voltage applied to the intermediate electrode 33 shown in (e), and the intermediate electrode 34 shown in (g) of FIG. Is expressed in the same manner as in FIG.

The change in the volume of the ink pressurizing chamber V1 shown in FIG. 7B is the same as that shown in FIG. 7B. That is, also in the ink jet head of this specific example, the ink pressurizing chamber operates at the times t1 and t
The operation of sucking and discharging the ink at the timing of 4, t7 is performed.

The same applies to the ink pressurizing chamber V2 shown in (d), and ink is sucked and discharged at the timings of times t2, t5 and t8. (F) Ink pressurizing chamber V3 shown in FIG.
At time t3, t6 and t9,
The ink is ejected at the next timing. Actually, as described above, each part of the ink jet head having many ink pressurizing chambers is drive-controlled.

In this specific example, unlike the conventional ink jet head as shown in FIG. 2, the edges of the upper common electrode 1, the intermediate electrode 32 and the lower common electrode 5 are exposed on the side surfaces. Since the left and right outermost walls of the head are not driven, the intermediate electrode 32 on that wall is not used for driving. However, this is pulled out to the rear end of the head together with the other intermediate electrodes as in the example of FIG. Therefore, in the same manner as in FIG. 2, the conductor 1 that short-circuits between the electrodes on one side of the head.
7, the upper common electrode 1, the intermediate electrode 32, and the lower common electrode 5 are short-circuited. With this, the intermediate electrode 32 is set to +
The above driving circuit can be realized by connecting to a power supply of V / 2.

<Effect of Specific Example 1> As described above, the upper and lower common electrodes at both ends of the wall separating the ink pressurizing chamber are short-circuited, and the wall is driven by the supply voltage to the intermediate electrode. Therefore, each wall is reliably electrically separated from each other, and is not affected by the movement of the other walls. In this case, each wall is driven and controlled by two switches, so that the size of the circuit can be reduced. Further, by providing a switch for short-circuiting each intermediate electrode, it is possible to forcibly make the volume of each ink pressurizing chamber constant, thereby enabling high-speed driving.
Also in this case, the number of switches connected to each intermediate electrode is reduced from the conventional three to 2.5 per one wall separating each ink pressurizing chamber, and the circuit scale of the drive unit is reduced. It is possible to reduce the size and cost.

<Embodiment 2> FIG. 12 is an explanatory view of the operation of the ink jet head of Embodiment 2. First, the structure of the ink jet head of this specific example will be described with reference to the cross-sectional view shown in FIG. As shown in the drawing, the structure of the upper top plate 27, the lower top plate 28, the upper common electrode 1, and the lower common electrode 5 is the same as that of the ink jet head of the first embodiment. The cross-sectional structure of the upper intermediate piezoelectric body 2 and the lower intermediate piezoelectric body 4 constituting each wall interposed therebetween is the same as that of the first embodiment. However, in this specific example, every other ink pressurizing chamber having an orifice is provided as shown in the figure.

That is, the ink pressurizing chamber VA having the orifice 22A is sandwiched between the wall driven by the intermediate electrode 3A and the wall driven by the intermediate electrode 3B. The ink pressurizing chamber VB provided with the orifice 22B is connected to the intermediate electrode 3
It is sandwiched between the wall driven by C and the wall driven by the intermediate electrode 3D. The ink pressurization chamber VC provided with the orifice 22C is sandwiched between a wall driven by the intermediate electrode 3E and a wall driven by the intermediate electrode 3F.

Each of the ink pressurizing chambers VA, VB, VC is sandwiched between a pair of walls that are completely electrically and mechanically independent. The space between the wall driven by the intermediate electrode 3B and the wall driven by the intermediate electrode 3C, and the space between the wall driven by the intermediate electrode 3D and the wall driven by the intermediate electrode 3E. , An ink channel (not shown) is sealed so that ink does not enter. Then, the intermediate electrodes 3A, 3 for driving each wall.
Drive units as shown in FIG. 13 are connected to B, 3C, 3D, 3E, and 3F, respectively.

FIG. 13 is a connection diagram of the ink jet head driving unit of the second embodiment. The drive unit shown in this figure is controlled by a switch control unit (not shown). The switch control is performed by a processor or the like as in the first embodiment. The driving unit in the figure includes switches SW1, SW2, SW3, SW4,
SW5 and + V volt power supply 12. Outputs of a pair of switches SW1 and SW2 are electrically connected to a terminal 7A. The outputs of the pair of switches SW3 and SW4 are electrically connected to the terminal 7B. The terminals 7A and 7B are electrically connected to intermediate electrodes 3A and 3B for driving a pair of walls sandwiching the ink pressurizing chamber VA, for example.

For each of the other ink pressurizing chambers VB and VC, one set of circuits having exactly the same connection as that shown in this figure is prepared. That is, in the case of this specific example, five switches are used for each ink pressurizing chamber. In addition, in the example of this figure, since the respective ink pressurizing chambers are electrically and mechanically independent from each other, they can be driven at any timing. Therefore, it is possible to freely control all the ink pressurizing chambers to simultaneously drive them to eject ink.

FIG. 14 is a timing chart of the operation of the driving section according to the second embodiment. As shown in the figure, in this specific example,
Each of the ink pressurizing chambers can be simultaneously controlled at exactly the same timing by exactly the same signal. For example, the control of the ink pressurizing chamber VB will be described. First, at time t1, the intermediate electrode 3C becomes 0 volt and the intermediate electrode 3D becomes + V volt. As a result, the walls are deformed as indicated by the broken lines in FIG. 12A, and the ink is sucked into the ink pressurizing chamber VB.
At time t2 of the next timing, the voltage of the intermediate electrode 3C becomes + V volt, and the voltage of the intermediate electrode 3D becomes 0 volt. Now Figure 1
As shown by a broken line in FIG. 2B, each wall is deformed and ink is ejected from the ink pressurizing chamber VB.

The operation of each of the switches SW1, SW2, SW3, SW4, and SW5 of the ink jet head driving section is the same as that of the first embodiment as shown in FIG. The function of the switch SW5 does not change. However, the difference is that the walls sandwiching all the ink pressurizing chambers can be driven freely at an independent timing. Therefore, a switch for electrically connecting the intermediate electrode of the wall for driving the adjacent ink pressurizing chamber, that is, FIG.
The switches SW6 and SW7 shown in (b) are unnecessary. In the above example, all the adjacent ink pressurizing chambers are simultaneously driven at the same time. However, it goes without saying that control can be performed at different timings according to the content of data to be printed. The appearance structure may be the same as that of the first embodiment.

<Effect of Embodiment 2> Also in this embodiment, the number of switches for driving one wall can be reduced to 2.5 compared to the conventional three switches. When compared in units of one ink pressurizing chamber, the number of switches required for control is larger than that of the conventional example, but each ink pressurizing chamber is freely controlled without being influenced by each other. This has the effect of simplifying other control circuits and control programs.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an ink jet head driving unit of a specific example 1.

FIG. 2 is a perspective view of an inkjet head.

FIG. 3 is a cross-sectional view of an inkjet head JJ of a comparative example.

FIG. 4 is a drive unit connection diagram of a comparative example.

FIG. 5 is a timing chart of the operation of a driving section according to a comparative example.

FIG. 6 is a diagram illustrating the operation of an inkjet head according to a comparative example.

FIG. 7 is a timing chart of an inkjet head according to a comparative example.

FIG. 8 is an explanatory diagram of the operation of the inkjet head according to the first embodiment.

FIG. 9 is a timing chart of the operation of the driving unit according to the first embodiment.

FIG. 10 is a diagram illustrating the operation of the ink pressurizing chamber.

FIG. 11 is a timing chart of the ink jet head according to the first embodiment.

FIG. 12 is an explanatory diagram of the operation of the inkjet head according to the second embodiment.

FIG. 13 is a connection diagram of an inkjet head driving unit according to a specific example 2.

FIG. 14 is a timing chart of the operation of the driving unit according to the second embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 upper common electrode 2 upper intermediate piezoelectric body 3 intermediate electrode 4 lower intermediate piezoelectric body 5 lower common electrode 6 ink pressurizing chamber 11 switch control unit 12 power supply SW1, SW2, SW3, SW4, SW5 switch

Claims (4)

[Claims] 1. An upper common electrode, an upper intermediate piezoelectric body group,
An intermediate electrode group, a lower intermediate piezoelectric body group, and a lower common electrode are sequentially laminated, and a pair of ink pressure chamber groups are partitioned by the upper intermediate piezoelectric body and the lower intermediate piezoelectric body sandwiching the intermediate electrode. Walls are formed, and all of the upper intermediate piezoelectric body and the lower intermediate piezoelectric body are sheared when an electric field is formed from the upper common electrode or the lower common electrode toward the intermediate electrode or in the opposite direction. The direction of the polarization axis is set so as to deform the mode, a predetermined bias voltage of the same potential is supplied to the upper common electrode and the lower common electrode, and the intermediate electrode of one of the pair of walls is A driving voltage higher than the bias voltage is supplied, and a driving voltage lower than the bias voltage is supplied to an intermediate electrode of the other wall of the pair of walls, whereby the wall is driven, and the wall is driven. If not so, the ink jet head, wherein an intermediate electrode of said pair of walls are electrically shorted together. 2. The ink jet head according to claim 1, wherein adjacent ink pressurizing chambers share a wall therebetween. 3. The ink-jet head according to claim 1, wherein adjacent ink pressurizing chambers are arranged with a space therebetween, and each ink pressurizing chamber is sandwiched by independent walls. Inkjet head. 4. An upper common electrode, an upper intermediate piezoelectric body group,
An intermediate electrode group, a lower intermediate piezoelectric body group, and a lower common electrode are sequentially stacked, and a pair of ink pressure chamber groups are partitioned by the upper intermediate piezoelectric body and the lower intermediate piezoelectric body sandwiching the intermediate electrode. Walls are formed, and all of the upper intermediate piezoelectric body and the lower intermediate piezoelectric body are sheared when an electric field is directed from the upper common electrode or the lower common electrode toward the intermediate electrode or in the opposite direction. A predetermined bias voltage of the same potential is supplied to the upper common electrode and the lower common electrode to the ink jet head in which the direction of the polarization axis is set so as to be mode-deformed. Starting from a state in which the electrodes are electrically short-circuited, a drive voltage higher than the bias voltage is supplied to the intermediate electrode of one of the pair of walls, and the other of the pair of walls is supplied with a drive voltage higher than the bias voltage. A drive voltage lower than the bias voltage is supplied to the inter-electrode, and ink is sucked into the ink pressurizing chamber. At the next timing, the intermediate electrode on one of the pair of walls is A drive voltage lower than the bias voltage is supplied, and a drive voltage higher than the bias voltage is supplied to the intermediate electrode on the other wall of the pair of walls to eject ink from the ink pressurizing chamber. And a method of driving an inkjet head, wherein both intermediate electrodes of the pair of walls are electrically short-circuited.