JP2000033693A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize multigradation printing through simple control. SOLUTION: Under normal print mode, printing is performed by applying a driving voltage to an electrode C(C') thereby deforming intermediate piezoelectrics 6, 7 (6', 7') in shearing mode. Under emphasis print mode, printing is performed by applying a driving voltage to electrodes B, C (B', C') thereby deforming projections 2 (2') and the intermediate piezoelectrics 5, 6, 7, (5', 6', 7') in shearing mode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head, and more particularly to an ink jet head which can easily control the diameter of ink droplets and is suitable for printing multi-tone images.

[0002]

2. Description of the Related Art Conventionally, ink jet printer heads have been disclosed in Japanese Patent Application Laid-Open Nos. 5-338156 and 6-842.
As disclosed in Japanese Unexamined Patent Application Publication No. 6-2006, there is one using a piezoelectric body. In this type of head, a pressurizing chamber for confining ink in a closed area and pressurizing the ink by a piezoelectric body is provided. The pressurizing chamber is provided with an inexpensive side wall, and the ink is pressurized by deforming the side wall in a shear mode by a piezoelectric body. The pressurized ink is ejected onto a print medium from an orifice provided at one end of the pressurized chamber.

[0003] This method is an ink pressurizing method by mechanical deformation of a piezoelectric material, so that the ink is not thermally degraded, and the deformation of the piezoelectric material can be controlled by adjusting the voltage. It is easy to control and it is strong against disturbance. Further, since the control of the ink pressing force enables the control of an appropriate amount of ink ejection and facilitates gradation printing, this method has recently attracted attention.

FIG. 2 is an overall perspective view showing the structure of a conventional ink jet head, and FIG. 3 is a sectional view showing the conventional ink jet head. The head includes a base piezoelectric body 41 made of lead zirconate titanate (PZT) or the like and a top plate 51.
With. A manifold 54 is formed on the ink suction port side of the top plate 51, from which ink is sucked into the ink pressurizing chamber 53 in the head. A sealing material 57 is formed on the manifold 54.

[0005] A nozzle plate 55 is attached to the tip of the head. The nozzle plate 55 is made of lead zirconate titanate (PZT), and has an orifice 56 at a position facing the ink pressurizing chamber 53. When the head is driven, ink is ejected from the orifice 56.

FIG. 4 is a cross-sectional view of the conventional ink jet head shown in FIGS. Base piezoelectric body 41
Are provided with a plurality of convex portions 42 (42 ') in a comb shape. An intermediate piezoelectric body 45 (45 ') made of PZT is provided on the protrusion 42 (42'). Thin film electrodes are formed above and below the convex portion 42 (42 ') and the intermediate piezoelectric body 45 (45').
The top of 2 ′) and the intermediate piezoelectric body 45 (45 ′) have their thin-film electrodes adhered by a conductive epoxy adhesive 47. Similarly, the top plate 51 side is bonded to the upper end of the intermediate piezoelectric body 45 (45 ′) with a conductive adhesive 47.

When such a conventional ink jet head is driven, as shown in FIG. 4, the common electrode 50 formed on the top plate 51 is grounded, a driving voltage V is supplied to the electrode 44, and the electrode 44 'is driven. Is supplied with the driving voltage −V, the direction indicated by the arrow E in FIG.
An electric field is applied in the direction from 2 to the convex portion 42 ', and the convex portion 42 and the intermediate piezoelectric body 45 each cause reverse shear mode deformation as shown by a broken line in FIG. Similarly, the protrusion 4
2 ′, the intermediate piezoelectric body 45 ′ undergoes a shear mode deformation opposite to that of the projection 42 and the intermediate piezoelectric body 45, respectively.

Accordingly, the ink in the ink pressurizing chamber 53 is pressurized, and the ink is ejected from the orifice 56.
Note that the arrow P in the figure indicates the polarization direction.

[0009]

However, in the above-described ink jet, the amount of change of the piezoelectric body when the voltage of the piezoelectric body is applied is determined by the applied voltage and the driving time. In order to perform gradation printing, a control table had to be provided for each voltage and time. In particular, when the droplet diameter is controlled by changing the applied voltage, a circuit for changing the power supply voltage must be added, and a satisfactory device has not been obtained. In addition, when only time is controlled, the setting range of the driving time is narrowed in consideration of the ink droplet ejection force and stability.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an ink jet head capable of realizing multi-tone printing with simple control.

[0011]

According to the present invention, there is provided an ink jet head having a first piezoelectric body having a comb-shaped uneven portion and polarized in an array direction, and a convex portion of the first piezoelectric body. A plurality of intermediate piezoelectric members provided in sequence via electrodes, a concave portion of the first piezoelectric member and an ink pressurizing chamber formed by each intermediate piezoelectric member, and ink pressurized in the ink pressurizing chamber is ejected. And an orifice.

In another ink jet head according to the present invention, a switching unit that switches whether each electrode is open or whether each electrode is connected to a voltage source or a ground potential, and controls switching by the switching unit. By controlling the first piezoelectric element and the intermediate piezoelectric elements to be subjected to shear mode deformation, the control section controls the amount of ink ejected from the orifice.

[0013]

FIG. 1 is a sectional view showing the structure of an ink jet head according to a first embodiment of the present invention.
FIG. 5 is an overall perspective view showing the structure of the ink jet head, and FIG. 6 is a sectional view showing the ink jet head.

As shown in FIG. 1, FIG. 5 and FIG. 6, this ink jet head has a lead zirconate titanate (P
ZT) and the like, and a top plate 11. A manifold 14 is formed on the ink suction port side of the top plate 11, and ink is supplied from the manifold 14 to the ink pressurizing chamber 1 in the head.
Inhaled in 3. A sealing material 17 is formed on the manifold 14.

A nozzle plate 15 is attached to the tip of the head. The nozzle plate 15 is made of lead zirconate titanate (PZT), and has an orifice 16 at a position facing the ink pressurizing chamber 13. When the head is driven, ink is ejected from the orifice 16.

As shown in FIG. 1, a plurality of convex portions 2 (2 ′) formed in a comb shape are provided on the surface of the base piezoelectric body 1. The protrusions 2 (2 ′) are arranged at equal intervals, and a groove 3 is formed between the adjacent protrusions 2 and 2 ′.

A thin film electrode B (B ') is formed on the top of the convex portion 2 (2') by vapor deposition. 6, 7
(5 ′, 6 ′, 7 ′) and the thin film electrodes A, C (A ′, C ′)
The layers are alternately laminated by being bonded with a conductive adhesive. The intermediate piezoelectric members 5, 6, 7 (5 ', 6', 7 ') are made of PZT, like the base piezoelectric members, and deform in a shear mode when a voltage is applied. In FIG. 1, between the convex portion 2 (2 ′) and the intermediate piezoelectric body 5 (5 ′), between the intermediate piezoelectric body 5 (5 ′) and the intermediate piezoelectric body 6 (6 ′), and between the intermediate piezoelectric body 6 (6 ′). ~ Intermediate piezoelectric body 7
The electrodes between (7 ′) are B, A, C (B ′, A ′,
C ′). On the intermediate piezoelectric body 7 (7 '), a top plate 11 having an electrode 10 formed on one side is provided with an electrode 10
And an intermediate piezoelectric body are provided by being bonded by a conductive adhesive.

At both ends of the groove 3 in the direction perpendicular to the paper,
An orifice 16 for ejecting ink and an ink inlet (not shown) for sucking ink from the manifold 14 are provided, and the ink pressurizing chamber 13 is formed by these and the groove 3.

As shown in FIG. 7, for example, as shown in FIG. 7, a driving system for driving the ink jet head configured as described above includes power supplies 21 and 22 for generating one system voltage for each of positive and negative, and a head 23.
Of the electrodes A, B, C, A ', B', C '
2, a switching unit 24 for selecting which of the ground potential to connect to or to float, and a control unit 2
5 is provided. The switching unit 24 includes, for example, a selector for selecting a connection destination or a floating state of each electrode for each electrode. The operation of each selector is controlled by the control unit 25 or controlled by a switching control unit included in the switching unit 24. Is done.

The operation modes of the ink jet head include a normal printing mode for printing at a predetermined gradation (normal printing) and an emphasized printing mode for printing at a gradation darker than the normal printing (emphasized printing). is there. The control unit 25 controls the driving of the head in each mode according to an external mode input.

FIGS. 8 and 9 are schematic diagrams showing the operation in each operation mode.

In the normal printing mode, the control unit 25
(A) and (B), a drive voltage is supplied to the electrodes C and C ′, the electrodes A and A ′ are grounded, and the electrodes B and
The switching unit 24 is controlled so that the driving voltage is not supplied to B ′. In this embodiment, the top 1
The common electrode 10 formed at 1 is grounded regardless of the operation mode.

As a driving voltage, a positive voltage (+
V), when a negative voltage (−V) is applied to the electrode C ′, FIG.
(A), an electric field is applied from the electrode C to the electrode A and from the electrode C to the electrode 10 as shown by an arrow E, and as shown in the figure, the electric field is applied to the intermediate piezoelectric body 6 and the intermediate piezoelectric body 7 respectively. Shear mode deformation occurs. At the same time, opposite shear mode deformations also occur in the intermediate piezoelectric body 6 ′ and the intermediate piezoelectric body 7 ′, respectively, and as shown in the figure, the volume of the ink pressurizing chamber 13 increases and a negative pressure is generated. Ink is sucked into the ink pressurizing chamber 13 via an ink inlet (not shown).

Next, when the polarity of the drive voltage supplied to the electrodes C and C 'is reversed, as shown in FIG. 8B, shear mode deformation occurs in the opposite direction to that in FIG. Then, the ink in the ink pressurizing chamber 13 is pressurized. By this pressurization, ink droplets are ejected from the orifice 16 and printing is performed.

In the highlight printing mode, the control unit 25
As shown in FIGS. 3A and 3B, the switching unit 24 is controlled so that a driving voltage is supplied to the electrodes B and B ′ and the electrodes C and C ′ and the electrodes A and A ′ are grounded. Control.

As the drive voltage, a positive voltage (+
V), when a negative voltage (−V) is applied to the electrodes B ′ and C ′, a negative pressure is generated in the ink pressurizing chamber 13 as shown in FIG. At this time, the amount of ink sucked into the ink pressurizing chamber 13 is determined by the difference between the sectional areas of the ink pressurizing chamber 13 shown in FIGS.
It can be seen that the value is about twice that of the case (A).

Next, when the voltages supplied to the electrodes B (C) and B '(C') are reversed, respectively, as shown in FIG. The shear mode deformation occurs, and the ink in the ink pressurizing chamber 13 is pressurized. By this pressurization, ink droplets are ejected from the orifice 16 as in the normal printing operation, and printing is performed.

By performing this series of operations, the amount of ink ejected from the orifice 16 by suction and pressurization of ink is twice as large as in the normal print mode, so that large ink droplets can be ejected. it can.

In the ink jet head according to this embodiment, electrodes are provided at both ends, and n 1 (n 1: a positive integer) of a plurality of intermediate piezoelectric bodies formed by lamination are deformed in a shearing mode. Print 1 (normal print)
And n2 of the intermediate piezoelectric bodies (n2> n1, n1
, N2: a positive integer) in the shear mode to perform the second printing (emphasized printing). That is, in the ink jet head according to this embodiment, electrodes are provided at both ends, and the discharge amount of ink is controlled by controlling the number of the intermediate piezoelectric bodies that are formed in a stack and deformed in the shear mode. Thus, the droplet diameter can be controlled and multi-gradation printing can be realized.

Therefore, in the ink jet head according to this embodiment, the type of the power supply voltage is positive (V) and negative (-V).
With only the two types, the droplet diameter of the ink can be controlled by selecting the application destination of the driving voltage, and multi-tone printing can be performed by a simple driving method.

FIG. 10 shows a change in the ink droplet diameter when the above-described control is performed using the ink jet head of this embodiment, and further the parameters of the driving time are controlled. In the same drawing, the droplet diameter when the ink jet head of this embodiment is used is indicated by a solid line, and the droplet diameter when the conventional ink jet head is used is indicated by a broken line. Therefore, by controlling the drive time in addition to the above-described control, the control range of the droplet diameter can be increased as compared with the related art.

In this embodiment, the number of laminations of the projections 2 and the intermediate piezoelectric layers 5, 6, and 7 has been described as four. Can be changed. For example, if the number of tones is to be increased, the number of layers is increased, and if the number of tones is small, the number of layers is reduced.

Second Embodiment An ink jet head according to a second embodiment has the same structure as the ink jet head shown in FIG. 1 described above, and is driven by a driving system having the same structure as that shown in FIG. The method of applying the drive voltage is different from that of the first embodiment.

FIGS. 11 and 12 are schematic diagrams showing the operation of the ink jet head according to the second embodiment.

In the normal printing mode, the control unit 25 shown in FIG.
Is the electrode B as shown in FIGS. 11A and 11B.
The switching unit 24 is controlled so that (B ′) and C (C ′) are grounded and a drive voltage is supplied to the electrode A (A ′). In this embodiment, the common electrode 10 formed on the top plate 11 is grounded regardless of the operation mode.

As a driving voltage, a positive voltage (+
V), when a negative voltage (−V) is applied to the electrode A ′, FIG.
As shown by an arrow E in (A), an electric field is applied from the electrode A to the electrode B, from the electrode A to the electrode C, from the electrode A 'to the electrode B', and from the electrode A 'to the electrode C'. As shown,
The opposite shear mode deformation occurs in the intermediate piezoelectric bodies 5 and 6, respectively. At the same time, the opposite shear mode deformation occurs in the intermediate piezoelectric body 5 ′ and the intermediate piezoelectric body 6 ′, respectively.
As shown in the figure, the volume of the ink pressurizing chamber 13 increases, a negative pressure is generated, and ink is sucked into the ink pressurizing chamber 13.

Next, when the polarity of the drive voltage supplied to the electrodes A and A 'is reversed, as shown in FIG. 11B, shear mode deformation occurs in the opposite direction to that in FIG. Then, the ink in the ink pressurizing chamber 13 is pressurized. By this pressurization, ink droplets are ejected from the orifice 16 and printing is performed.

In the highlight printing mode, the control unit 25 shown in FIG.
Is the electrode B as shown in FIGS. 12A and 12B.
(B ') and C (C') are disconnected from both the ground potential and the power supply and become floating, and the electrode A (A ')
So that the switching voltage is supplied to the
Control.

As a drive voltage, a positive voltage (+
V), when a negative voltage (-V) is applied to the electrode A ', the electrodes B and C are in a floating state, so that the intermediate piezoelectric body 5 is the base piezoelectric body 1 and the intermediate piezoelectric body 6 is the intermediate piezoelectric body 6. Shear mode deformation occurs integrally with the body 7. At this time, as indicated by an arrow E in FIG.
From the intermediate piezoelectric body 5 toward the convex portion 2 of the base piezoelectric body 1,
Further, an electric field is applied from the convex portion 2 'toward the intermediate piezoelectric body 5', and as shown in the drawing, the intermediate piezoelectric body 5, the convex section 2, the intermediate piezoelectric body 6, and the intermediate piezoelectric body 7 have the opposite shear mode. Cause deformation. At the same time, the opposite shear mode deformation occurs in the intermediate piezoelectric body 5 ′, the convex portion 2 ′, the intermediate piezoelectric body 6 ′, and the intermediate piezoelectric body 7 ′, and the ink is sucked into the ink pressurizing chamber 13. The amount of ink suction here is about twice as large as in the normal print mode.

Next, when the polarity of the driving voltage supplied to the electrodes A and A 'is reversed, as shown in FIG. 12B, shear mode deformation occurs in the opposite direction to that in FIG. Then, the ink in the ink pressurizing chamber 13 is pressurized. By this pressurization, ink droplets are ejected from the orifice 16 and printing is performed.

By performing this series of operations, the amount of ink ejected from the orifice 16 by suction and pressurization of ink is twice as large as that in normal printing, so that large ink droplets can be ejected. Can be.

By the way, from the relationship between the applied voltage and the displacement of the piezoelectric body, the amount of pressure displacement (volume that changes by pressurization) in the emphasis printing operation of this embodiment and the first embodiment is the same ( 9 (B) and 12 (B)). That is, the amount of displacement of the piezoelectric body is proportional to the applied voltage V and inversely proportional to the distance between the applied electrodes. In FIG. 9B and FIG. 12B, focusing on one intermediate piezoelectric body, FIG.
In (B), the applied voltage is 1/2 V, and the distance between the applied electrodes is twice (for two layers). On the other hand, in FIG. 9B, the applied voltage is V and the distance between the applied electrodes is one layer. However, the volume changes in the first embodiment and the second embodiment are the same.

In the ink jet head according to this embodiment, similarly to the first embodiment, electrodes are provided at both ends, and n1 (n) of a plurality of stacked intermediate piezoelectric bodies are formed.
The first printing (normal printing) is performed by deforming (1: a positive integer) in the shear mode, and n2 (n2> n1, n2: a positive integer) of the intermediate piezoelectric bodies are deformed in the shear mode. Thus, the second printing (emphasized printing) can be performed. That is, in the ink jet head according to this embodiment, electrodes are provided at both ends, and the discharge amount of ink is controlled by controlling the number of the intermediate piezoelectric bodies that are formed in a stack and deformed in the shear mode. Thus, the droplet diameter can be controlled and multi-gradation printing can be realized.

As described above, in the ink-jet head according to this embodiment, the type of the power supply voltage is positive, negative 2
Even if only the type is used, the droplet diameter of the ink can be controlled by selecting the application destination of the driving voltage, and multi-tone printing can be performed by a simple driving method.

FIG. 13 shows the change in the ink droplet diameter when the above-described control is performed using the ink-jet head of this embodiment and the driving time parameter is further controlled. In the same drawing, the droplet diameter when the ink jet head of this embodiment is used is indicated by a solid line, and the droplet diameter when the conventional ink jet head is used is indicated by a broken line. Therefore, by controlling the drive time in addition to the above-described control, the control range of the droplet diameter can be increased as compared with the related art.

By the way, in the first embodiment, as shown in FIG. 10 described above, the droplet diameter varies during the emphasis printing.

This is because, in the first embodiment, FIG.
This is because, as shown in (1), the deformed portion of the piezoelectric body (the boundary between the intermediate piezoelectric bodies 6 and 7 and the boundary between the intermediate piezoelectric body 5 and the convex portion 2) for pressurizing the ink exists above and below the orifice.

If the pressures above and below the orifice are always the same, the droplets ejected from the orifice will have the same shape, but since various conditions overlap, the pressures above and below are not always constant in practice. . Therefore, the pressure transmitted to the orifice is slightly different, the shape of the ejected droplet is different, and affects the droplet diameter. This tends to cause variations.

On the other hand, in the second embodiment, as shown in FIG. 12 described above, the deformed portion of the piezoelectric body for pressurizing the ink exists at the center (the boundary between the intermediate piezoelectric bodies 5 and 6). Therefore, the pressure transmitted to the orifice does not become uneven in the vertical direction, and the droplet diameter is relatively stable as shown in FIG.

Third Embodiment An ink-jet head according to a third embodiment is configured similarly to the above-described ink-jet head shown in FIG. 1, but the method of applying a drive voltage is the same as that of the above-described first and second ink-jet heads. Different from the embodiment.

The drive system shown in FIG. 7 has power supplies 21 and 22 for generating one voltage for each of the positive and negative sides. The drive system for driving the third ink jet head is as shown in FIG. And power supplies 31, 32, 33, and 34 for generating two positive and negative voltages. This drive system includes a control unit 36 and a switching unit 35 as in FIG. Note that power supplies of more systems may be provided according to the number of stacked electrodes and the number of gradations.

In the first or second embodiment described above, there are two modes of the normal printing operation and the emphasized printing operation. However, in this embodiment, as shown in the following table, six modes are provided. have.

[Table 1]

In the mode 1, first, as shown in FIG. 15A, the control unit 36 in FIG. 14 controls the switching unit 35 to ground the electrode 10 and drive voltage to the electrode C (C '). V
(−V), and a drive voltage of 2 V (−) is applied to the electrode A (A ′).
2V) and drive voltage V (-V) is applied to electrode B (B ').
Supply. When each voltage is supplied, the intermediate thick electric layer 6,
7 (6 ′, 7 ′) and the intermediate piezoelectric layers 2, 5 (2, 5 ′) are integrally deformed in shear mode. Thereby, the ink is sucked into the ink pressurizing chamber 13. Here, the driving voltage applied to the electrodes C and C ′ is the same as that in FIG.
The shear mode deformation of the intermediate piezoelectric layer is about twice that of FIG. 12 as shown in FIG.

Next, as shown in FIG. 15B, the control unit 36 controls the switching unit, and the driving voltage −V (V) is supplied to the electrode C (C ′), and the electrode A (A ′) Drive voltage -2
V (2 V) is supplied, and the driving voltage −V is applied to the electrode B (B ′).
When (V) is supplied, the intermediate thick electric layers 6 and 7 and the intermediate piezoelectric layers 2 and 5 undergo shear mode deformation in the direction opposite to that of FIG.

In this mode 1, the same operation can be performed even when the electrodes C and B are in a floating state. This is because the driving voltage applied between the electrode 10 and the electrode A is 2 V, the potential of the electrode C is V as a result of the measurement, and the potential difference between the electrode A and the electrode A ′ is 4 V, The potential difference between electrode B and electrode A 'is V
This is because It is not desirable to keep the electrodes floating in circuit design.

In the mode 2, first, the control unit 36 controls the switching unit 35 to supply the drive voltage V to the electrodes B, C and D, and to apply the drive voltage −V to the electrodes B ′, C ′ and D ′. Supply.
When such a drive voltage is supplied, as shown in FIG. 16A, the intermediate thick electric layer 7 (7 ′) and the intermediate piezoelectric layer 2
(2) is deformed in shear mode because the voltages at both ends thereof are different, but the intermediate piezoelectric layer 5 (5 ′) and the intermediate piezoelectric layer 6
(6 ') does not deform in shear mode because the voltages at both ends are almost equal. Thereby, the ink is sucked into the ink pressurizing chamber 13.

The voltages of the electrodes C, A, and B are all V
Since the voltages of the electrodes C ′, A ′, and B ′ are all −V, the same operation can be realized even when the electrodes A and A ′ are in a floating state. It is not desirable to keep the electrodes floating in circuit design.

Next, as shown in FIG. 16B, the control unit 36 controls the switching unit to supply a driving voltage -V to the electrodes B, C, and D, and the electrodes B ', C', and D '. Is supplied with a drive voltage V. When such a drive voltage is supplied, the intermediate thick electric layer 7 (7 ′) and the intermediate piezoelectric layer 2 (2) are connected to each other as shown in FIG.
However, the intermediate piezoelectric layer 5 (5 ′) and the intermediate piezoelectric layer 6 (6 ′) do not undergo shear mode deformation. As a result, the ink in the ink pressurizing chamber 13 is pressurized and ejected from the orifice 16.

In modes 3 to 6, as in the above-described first and second embodiments, two positive and negative power supplies (V, -V) are used.
Use only In the mode 3, the control unit 36 performs the same control as that in the highlight printing operation of the first embodiment shown in FIG. 9 described above. In the mode 4, the control unit 36 performs the same control as in the normal printing operation of the above-described second embodiment shown in FIG. In the mode 5, the control unit 36 performs the same control as that in the normal printing operation of the first embodiment shown in FIG. 8 described above.

In the mode 6, the control unit 36 drives the electrodes B and B ', as shown in FIGS. 17A and 17B, symmetrically with the normal printing operation of the first embodiment. Voltage is supplied and electrodes A, A 'and electrodes C, C' are grounded,
The switching unit 35 is controlled. In this mode, the common electrode 10 formed on the top plate 11 is grounded.

When a positive voltage (+ V) is applied to the electrode B and a negative voltage (−V) is applied to the electrode B ′ by switching of the switching unit 35, as shown by an arrow E in FIG.
, An electric field is applied from the electrode A and the electrode B toward the convex portion 2, and reverse shear mode deformation occurs in the intermediate piezoelectric body 5 and the convex portion 2 as shown in FIG. At the same time, opposite shear mode deformations also occur in the intermediate piezoelectric body 5 ′ and the protrusions 2 ′, respectively, and as shown in FIG. Is sucked into the ink pressurizing chamber 13.

Next, when the control unit 36 reverses the polarity of the driving voltage supplied to the electrodes B and B ', as shown in FIG. 17B, the shearing is performed in the opposite direction to that of FIG. A mode deformation occurs, and the ink in the ink pressurizing chamber 13 is pressurized.
By this pressurization, ink droplets are ejected from the orifice 16.

In each of the above modes, one side wall of the ink pressurizing chamber 13 formed by the convex portion 2 and the electrodes 5, 6, and 7 changes from a static state (the state shown in FIG. 1) to a pressurized state (FIG. 15B).
16 (B), FIG. 9 (B), FIG. 11 (B), FIG.
(B), the change in the cross-sectional area of the ink pressurizing chamber 13 when the state shown in FIG. 17B is reached, where h is the thickness of one intermediate piezoelectric layer, and the drive voltage V is applied. When the shear mode displacement of the intermediate piezoelectric material for one layer at the time of the above is compared with x, the following is obtained.

[Table 2]

Since the amount of ink discharged is proportional to the change in the cross-sectional area of the ink pressurizing chamber 13, the change in the cross-sectional area indicates the ratio of the amount of ink to be discharged. Since the volume change ratios are the same in modes 4 to 6, the ink ejection amounts are the same.

As described above, in the ink jet head according to this embodiment, the voltage supplied to each electrode is
By selecting one of the power supply voltage and the ground potential for each of the two systems for positive and negative, printing of four gradations can be realized. Therefore, two positive and negative power supplies are required,
Multi-tone printing can be realized by a simple control method.

In this embodiment, the power supply voltage is described as having two systems of positive and negative. However, by further increasing the number of systems of the power supply voltage, printing with more gradations can be realized. Further, in this embodiment, the number of laminations of the protrusions 2 and the intermediate piezoelectric layers 5, 6, and 7 has been described as 4. However, the number of laminations can be changed by appropriately changing the number of printable gradations. be able to. Further, by controlling the drive time of the side wall of the ink pressurizing chamber, it is possible to further contribute to increase the number of printable gradations.

[0067]

The ink jet head according to the present invention has the following features.
A first piezoelectric body having a comb-shaped uneven portion and polarized in the array direction, a plurality of intermediate piezoelectric bodies provided sequentially on the convex portion of the first piezoelectric body via electrodes, Since there is an ink pressurizing chamber constituted by the concave portion of the piezoelectric body and each intermediate piezoelectric body, and an orifice for ejecting the ink pressurized in the ink pressurizing chamber, the first piezoelectric body and each intermediate piezoelectric body The body movement can be controlled independently, the amount of ink ejected from the orifice can be easily controlled, and multi-tone printing can be easily realized.

In another ink-jet head according to the present invention, the control unit controls the switching by the switching unit to control the first piezoelectric body and the intermediate piezoelectric bodies that are subjected to shear mode deformation. Since the amount of ink ejected from the orifice is controlled, multi-tone printing can be realized by simple control.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an inkjet head according to a first embodiment of the present invention.

FIG. 2 is a perspective view illustrating a configuration of a conventional inkjet head.

FIG. 3 is a cross-sectional view illustrating a configuration of a conventional inkjet head.

FIG. 4 is a cross-sectional view illustrating a configuration of a conventional inkjet head.

FIG. 5 is a perspective view illustrating a configuration of the inkjet head according to the first embodiment.

FIG. 6 is a cross-sectional view illustrating a configuration of the inkjet head according to the first embodiment.

FIG. 7 is a block diagram illustrating a configuration of a drive system that drives the inkjet head according to the first embodiment.

FIG. 8 is a cross-sectional view illustrating an operation of the inkjet head according to the first embodiment in a normal print mode.

FIG. 9 is a cross-sectional view illustrating an operation of the inkjet head according to the first embodiment in an emphasis print mode.

FIG. 10 is a diagram illustrating a relationship between a driving time and a droplet diameter of the inkjet head according to the first embodiment.

FIG. 11 is a cross-sectional view illustrating an operation of the inkjet head according to the second embodiment in a normal print mode.

FIG. 12 is a cross-sectional view illustrating an operation of an ink jet head according to a second embodiment in an emphasis printing mode.

FIG. 13 is a diagram illustrating a relationship between a driving time and a droplet diameter of an inkjet head according to a second embodiment.

FIG. 14 is a block diagram illustrating a configuration of a drive system that drives an inkjet head according to a third embodiment.

FIG. 15 is a cross-sectional view illustrating an operation of a mode 1 of the inkjet head according to the third embodiment.

FIG. 16 is a cross-sectional view illustrating an operation of a mode 2 of the inkjet head according to the third embodiment.

FIG. 17 is a cross-sectional view illustrating an operation of a mode 6 of the inkjet head according to the third embodiment.

[Explanation of symbols]

1 Base piezoelectric body, 2, 2 'convex portion, 5, 6, 7, 5',
6 ', 7' intermediate piezoelectric body, 10, A, B, C, A ', B',
C 'electrode, 11 top plate, 13 ink pressurizing chamber, 16
Orifice

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Toshiyuki Asaka 4-11-22 Shibaura, Minato-ku, Tokyo F-term in the offshore company data (reference) 2C057 AF39 AG12 AG45 AM03 AM15 AM18 AR16 BA03 BA14 CA01

Claims (4)

[Claims] 1. A first piezoelectric body having a comb-shaped uneven portion and polarized in an array direction, and a plurality of intermediate members provided on the convex portion of the first piezoelectric body in sequence via electrodes. A piezoelectric body; a pressurizing chamber for ink constituted by a concave portion of the first piezoelectric body and an intermediate piezoelectric body; and an orifice for ejecting the ink pressurized in the pressurizing chamber. Inkjet head. 2. A switching unit for switching whether each of the electrodes is open or whether each electrode is connected to a voltage source or a ground potential, and controlling the switching by the switching unit.
2. The control device according to claim 1, further comprising a control unit configured to control one of the first piezoelectric body and the intermediate piezoelectric bodies that undergoes a shear mode deformation and control an amount of ink ejected from the orifice. 3. Ink jet head. 3. The ink jet head according to claim 2, wherein the control unit controls the amount of the ink according to printing conditions. 4. The ink jet head according to claim 2, further comprising a plurality of said voltage sources each generating a different voltage.