JP3121281U - Share mode ink head - Google Patents

Abstract

A sufficient pressure is ensured in an ink chamber when a shear mode ink head made of a piezoelectric material is driven.
A shear mode ink head includes a plurality of partition walls made of piezoelectric material, a base portion made of piezoelectric material on the bottom side of the partition walls, a lid body on the upper side of each partition wall, and ink discharge chambers. It has an individual electrode 8 on the inner surface and a common electrode 6 on the lower surface of the base. A voltage equivalent to the voltage applied to the individual electrode of the ink ejection chamber to eject ink is always applied to the common electrode. Since pressure is also applied to the inside of the ejection side ink ejection chamber from the deformed partition walls and the bottom side, the ink in the ejection chamber is sufficiently pressurized, the ink ejection force and its uniformity are sufficient, and high reliability High quality printing over a long period of time.
[Selection] Figure 1

Description

  The present invention selectively applies a predetermined voltage to the inner surfaces of a plurality of ink discharge chambers partitioned by a plurality of partition walls made of a piezoelectric material, and causes the partition to deform in a shear mode so that a desired ink discharge chamber can be formed. The present invention relates to a share mode ink head that ejects ink by changing its volume.

  Among the non-impact printers that are expanding their market today, there is an ink jet printer that has the simplest principle and is suitable for color printing. As an ink jet head (hereinafter also referred to as an ink head), The Kaiser type disclosed in the following Patent Document 1 or the thermal jet type disclosed in the following Patent Document 2 exist as typical systems. Among these, the former has a very difficult problem that it is difficult to reduce the size, and the latter has a problem that the ink burns because high heat is applied to the ink.

  As a method for simultaneously solving the above-described defects, Japanese Patent Application Laid-Open No. 63-252750 discloses a structure using a strip of a piezoelectric material, and a shear mode using a deformation mode of the strip. A type of ink head has been proposed.

As one configuration example of the share mode type ink head, a plurality of groove portions partitioned by partition walls are formed in the piezoelectric material so as to be parallel to each other, and electrodes are formed on the inner surfaces of these groove portions to selectively generate a predetermined voltage. For example, an ink chamber having an opening as a nozzle is formed in the front by closing the opened groove with a lid. According to such a configuration, if ink is filled in the ink chamber and a voltage is selectively applied to the electrodes to cause deformation of the shear mode in the partition wall, the volume of the ink discharge chamber is changed and ink is discharged from the nozzles of the ink discharge chamber. It can be discharged.
Japanese Patent Publication No.53-12138 Japanese Examined Patent Publication No. 61-59914 JP-A-63-252750

  In an ink head using a piezoelectric material including the share mode ink head, the temperature of the piezoelectric body portion increases due to continuous driving, which adversely affects driving and ink. Further, when the partition wall is driven greatly, ink is ejected from the adjacent ink chamber, which may cause deterioration in print quality. Therefore, it is necessary to solve the various problems by expanding the deformation range and generating the same volume change as before with less displacement.

  On the other hand, lead-containing oxides such as lead zirconate titanate (PZT) are widely used as the piezoelectric material. However, with the aim of realizing an environmentally friendly society, international agreements have been made to promote lead-free technology in all technologies, so that only piezoelectric materials are exceptionally undeveloped because materials that can replace PZT are exceptionally undeveloped. However, lead-free piezoelectric materials are now an urgent technical issue. In general, since lead-free piezoelectric materials do not reach the performance of lead-based materials (for example, piezoelectric constant), in order to perform the same ink ejection, it is necessary to overcome it by devising the structure.

  In response to the above-mentioned social demands, the present inventor has been eagerly researching the lead-free structure of piezoelectric materials for ink heads. In the present invention, the present structural problem of share mode ink heads for lead-based piezoelectric materials has been solved. However, the pressure of the ink chamber when driving the shear mode ink head composed of lead-free piezoelectric material is stabilized and sufficiently secured, and there is a problem of lack of ink droplet ejection force or uniformity and lack of reliability. It is an object of the present invention to provide a highly reliable inkjet head that can solve the problem and stably perform high-quality printing over a long period of time.

The share mode ink head according to claim 1,
A plurality of partition walls made of piezoelectric material arranged at predetermined intervals, a base portion made of a piezoelectric material commonly provided on the bottom side of each partition wall, a lid provided on the upper side of each partition wall, and An electrode provided on an inner surface of an ink discharge chamber partitioned by a partition wall, the base portion, and the lid, and applying a predetermined voltage to the electrode causes a shear mode deformation of the partition wall. In the share mode ink head that discharges ink from the ink discharge chamber by changing the volume of the discharge chamber,
A common electrode to which a voltage equivalent to a voltage applied to the electrode of the ink discharge chamber to which ink is to be discharged is constantly applied is provided on the lower surface of the base portion.

The share mode ink head according to claim 2 is the share mode ink head according to claim 1,
A second base made of a piezoelectric material is provided on the lower surface of the common electrode.

The share mode ink head according to claim 3 is the share mode ink head according to claim 1 or 2,
When the voltage applied to the electrode and the common electrode is constant, the thickness of the partition wall in the direction of the potential due to the voltage is set to 60 to 80 μm.

  According to a fourth aspect of the present invention, there is provided a shear mode ink head according to the first to third aspects, wherein the piezoelectric material is a piezoelectric material not containing a lead component.

  The shear mode ink head described in claim 5 is the share mode ink head according to claims 1 to 3, wherein the piezoelectric material is a piezoelectric material containing a lead component.

  According to the shear mode ink head described in claim 1, the common electrode on the lower surface of the piezoelectric material at the bottom of each partition partitioning the ink discharge chamber is applied to the electrode of the ink discharge chamber during ink discharge. Since an equivalent voltage is always applied, pressure is applied not only to the deformed partition walls on the both sides but also to the inside of the ink ejection chamber to be ejected. Therefore, the ink in the ink discharge chamber is sufficiently pressurized, the ink droplet discharge force or its uniformity is sufficient, and high-quality printing can be performed over a long period of time with high reliability.

  According to the shear mode ink head described in claim 2, in the share mode ink head according to claim 1, the second base portion made of a piezoelectric material is provided on the lower surface of the common electrode. A significant increase in the pressure in the discharge chamber can be achieved.

  According to the share mode ink head described in claim 3, in the share mode ink head according to claim 1 or 2, in the case where the voltage applied to the electrode and the common electrode is constant, the potential caused by the voltage. If the thickness of the partition in the direction of 60 to 80 [mu] m is set, the highest pressure increase in the ink discharge chamber during ink discharge when other conditions are made constant can be achieved.

  According to the shear mode ink head described in claim 4, in the shear mode ink head according to claims 1 to 3, since the piezoelectric material is a piezoelectric material containing no lead component, addition to the environment is possible. In addition, the ink chamber pressure is stabilized and sufficiently secured while solving the problem of insufficient ink droplet ejection force or uniformity and lack of reliability, and stable high-quality printing over a long period of time. High reliability can be realized.

  The share mode ink head described in claim 5 is the share mode ink head described in claims 1 to 3, which solves the structural problem of the current lead mode piezoelectric material share mode ink head and stabilizes the pressure in the ink chamber. In addition, the problem of insufficient ink droplet ejection force or uniformity and lack of reliability can be solved, and high reliability capable of stably performing high-quality printing over a long period of time can be realized.

1. Structure of this Example Share Mode Ink Head An embodiment of the present invention will be described with reference to FIGS.
A share mode ink head 1 according to the embodiment shown in FIG. 1 includes a plurality of partition walls 2 made of a lead-free piezoelectric material arranged at predetermined intervals, and a lead-free common provided on the bottom side of each partition wall 2. A plate-like base 3 made of a piezoelectric material and a plate-like lid 4 provided on the upper side of each partition wall 2 have a structure in which a large number of ink discharge chambers 5 having a rectangular cross section are defined. Accordingly, the ink discharge chambers 5 are arranged at predetermined intervals in a direction orthogonal to the longitudinal direction.

  The partition wall 2 is divided at the center in the vertical direction (vertical direction in FIG. 1) perpendicular to the direction in which the ink discharge chambers are arranged (left and right direction in FIG. 1). As shown by, each has a polarization direction toward the center in the longitudinal direction. Further, the polarization direction of the base portion 3 is upward in the vertical direction as in the lower half portion of the partition wall 2 in contact with the base portion 3.

The base 3 and the lower half of the partition wall 2 may be integrally formed from one piezoelectric material, or may be formed from separate materials.
In the case of integrally forming, for example, a pair of piezoelectric material plates whose polarization directions are opposite to each other like the partition wall 2 described above are bonded together, and the plate material surface is passed through this bonding surface. Grooves having a parallel direction as a longitudinal direction are formed parallel to each other at a predetermined interval, and the portions left between the grooves are defined as the partition walls 2, and the plurality of groove sections partitioned by the plurality of partition walls 2 are the ink discharge chambers 5. And In the above process, the groove is formed by opening on the surface of one of the plate members, and the cover 4 is covered with the opening so that each groove serves as a space for the ink discharge chamber 5. A nozzle having an appropriate diameter is provided at one end of the groove-shaped ink discharge chamber 5 for discharging ink, and a common ink chamber is connected to each ink discharge chamber 5 at the other end. The discharge chamber 5 is configured to be always supplied and filled with ink.

  FIG. 1 is a diagram showing this example and other embodiments (configuration examples) in common in one figure. That is, in FIG. 1, the common electrode 6 is provided on the lower surface of the base portion 3, and the second base portion 7 is further provided below the common electrode 6, and is formed between two plate-like base portions of the first base portion 3 and the second base portion 7. Although it is drawn so that one common electrode 6 in the form of a layer exists, in this example, it is a structure having only the base 3 (first base) and the common electrode 6 provided on the lower surface thereof, The structure is such that a plurality of base portions are not stacked. Hereinafter, the structure of the first example is also referred to as a “no stacking” type.

  In the share mode ink head of the second example, as described above, one common electrode 6 exists between the two bases of the first base 3 and the second base 7, and a plurality of plates In this structure, the bases are stacked with one common electrode in between. Hereinafter, such a structure of the second example is also referred to as a “stacked” type. And this "lamination" type is considered to be the absence of the horizontal alternate long and short dash line L displayed in the second base portion 7 of FIG. 1, and the second base portion 7 is a single layer ( It is considered that this alternate long and short dash line L exists as a boundary between different layers, and the second base portion 7 has a two-layer structure of the same material (when the second base portions 7a and 7b are included). There are two cases (two layers). When the number of layers is one, the thickness of the second base 7 can be variously set as will be described in an example described later in both cases.

  As shown in FIG. 1, continuous individual electrodes 8 are provided on the inner surface of a pair of opposing partition walls 2 and the inner surface (bottom surface) of the base 3 which are the inner surfaces of the ink discharge chamber 5 so as to be electrically integrated. Yes. The individual electrode 8 is configured to be given a predetermined voltage as required. In this example, when ink is ejected, a potential of +20 V is applied to the potential 0 V of the individual electrode 8 in the adjacent ink ejection chamber.

  As described above, the lower surface of the base portion 3 has a voltage equivalent to the voltage applied to each individual electrode 8 of each ink discharge chamber 5 during ink discharge (in this example, +20 V or equivalent to this). A common electrode 6 to which a potential difference is always applied is provided. In this way, the portion constituting the lower side of the ink discharge chamber 5 is made of a piezoelectric material, and the common electrode 6 is provided on the portion and a voltage is constantly applied thereto. Therefore, pressure is always applied to the inside of the ink discharge chamber 5 from the bottom surface inside the ink discharge chamber 5 from which ink is to be discharged.

2. Operational Effect of the Share Mode Ink Head 1 The operation in this example will be described.
In the structure of the partition wall 2 including the setting of the polarization direction in this example, a potential of +20 V is applied to the common electrode 6 of the base 3, and a potential of +20 V is applied to the individual electrode 8 of the ink ejection chamber 5 where ink is to be ejected. To eject ink. That is, when the potential of the individual electrode 8 in the adjacent ink discharge chamber 5 is set to 0 V, and the potential of +20 V is applied to the individual electrode 8 of the ink discharge chamber 5 selected to discharge ink, the partition wall 2 of the ink discharge chamber 5 Due to the interaction between the electric field generated by the electric potential and the polarization direction of the piezoelectric material of the partition wall 2, a shear mode deformation is generated which is displaced inward as shown in FIG. The stored ink is ejected from a nozzle (not shown) as ink droplets in a direction perpendicular to the paper surface in FIG.

  Here, since the base 3 receives a force in a direction to be deformed upward by energization of the common electrode 6, pressure is applied to the inside of the ink discharge chamber 5 from which ink is to be discharged from the bottom surface side. Therefore, according to this example, when ink is ejected due to the volume reduction of the ink ejection chamber 5 due to deformation of the partition wall 2, the pressure applied to the ink in the ink ejection chamber 5 is also added to the pressure from the base 3. As compared with a case where no special measures are taken, the ink ejection force is further increased, the uniformity of ink droplet ejection is stable, and high reliability capable of high-quality printing over a long period of time is achieved.

  Further, in the share mode ink head 1 as in this example, when the common electrode 6 is not provided on the bottom surface of the base portion 3, the base portion 3 of the adjacent ink discharge chamber 5 that does not discharge ink sinks downward due to the deformation of the partition wall 2. For this reason, the internal volume of the ink discharge chamber 5 that does not discharge ink becomes too large, and the pressure change in the adjacent ink discharge chamber 5 that discharges ink becomes excessive, and the difference in the ink discharge amount from the desired set amount is caused. It will cause it. However, according to this example (for example, when one layer of electrodes is inserted), by applying a voltage to the common electrode 6 of the base portion 3 of the piezoelectric material at all times, the base portion 3 that supports the partition wall 2 that is deformed for ink ejection is applied. Since the force always works upward, excessive deformation of the partition wall 2 during ink ejection is suppressed, and an error from a desired set amount is less likely to occur in the ink ejection amount.

The lead-free piezoelectric material used in this example is made of, for example, a barium titanate (BaTiO ₃ ) polycrystal, and Si, Al, Mg, etc. that are inevitably mixed during raw material preparation or sintering. Contains a trace amount. It also includes a composition in which Ba or Ti is intentionally substituted with a trace amount of the third component. However, the lead-free piezoelectric material of this example is not limited to this, and other configurations may be used as long as they are lead-free.

  Although this example mainly describes the effects of lead-free piezoelectric materials, the piezoelectric material in the present invention can be applied not only to lead-free piezoelectric materials but also to lead-containing piezoelectric materials in the same manner as the above-described example. It is. With regard to piezoelectric materials containing lead, commercially available lead zirconate titanate (PZT), lead titanate (PT), lead zirconate (ZT), etc., and relaxor-type compounds can also function with this structure.

3. Confirmation of operational effects by experiment of share mode ink head 1 In the “no lamination” type share mode ink head 1 of this example, the thickness of the partition wall 2 made of piezoelectric material and the effect of increasing the ink discharge pressure due to this In order to confirm the relationship, the thickness of the partition wall 2 made of a piezoelectric material was changed, and the change amount (%) of the displacement of the partition wall 2 during energization and the change amount (%) of the pressure in the ink discharge chamber 5 were measured. The relationship between the thickness of the partition wall 2, the change amount (%) of the displacement of the partition wall 2, and the change amount of the pressure in the ink discharge chamber 5 was examined.

The dimensions of each part of the share mode ink head 1 in this example are as illustrated in FIG. 1, and the height of the ink discharge chamber 5 (that is, the dimension in the height direction of the partition wall 2) is the upper or lower partition wall. Since the height of 2 is 155 μm, it is 155 × 2 μm. The width of the ink discharge chamber 5 (that is, the interval between the adjacent partition walls 2) is 75 μm. The thickness of the partition wall 2 (that is, the dimension in the adjacent direction of the partition wall 2) is changed by ± α around 100 μm, and the above-described amounts are measured. Further, in the non-stacked type, the thickness of the base 3 is arbitrary. In the stacked type, when the number of stacked layers is one, the thickness of the second base portion 7 having a single layer structure is 80 μm. When the number of stacked layers is two layers, the layers 7a and 7b of the second base portion 7 having a two layer structure are used. The thickness of each is 40 μm, and the total thickness is 80 μm.
Note that the drive voltage may be constant, or the electric field may be constant by changing the voltage according to the thickness of the partition wall 2.

(1) "No lamination" type (see Fig. 2)
As shown in FIG. 2, the share mode ink head 1 of this example in which the thickness of the partition wall 2 is set to any 15 to 16 points within the range of 40 to 160 μm is actually driven under the same conditions, and the displacement of the partition wall 2 The ink discharge pressure was examined, and the amount of change was displayed as a plus or minus% with reference to the case where the thickness of the partition 2 was 100 μm.

According to FIG. 2, when the electric field is constant, the ink discharge pressure increases as the thickness of the partition wall 2 (“piezoelectric portion thickness” in the figure) increases in both pressure and displacement. In the range of the partition wall 2, when the partition wall 2 thickness is 100 μm, the pressure is approximately in the range of −65% to + 20%, and the displacement is approximately in the range of −30% to + 20%.
Therefore, under the condition of a constant electric field, it is advantageous that the partition wall 2 is thicker from the viewpoint of ensuring a sufficient ink discharge pressure.

According to FIG. 2, when the voltage is constant, the ink discharge pressure decreases as the thickness of the partition wall 2 (“piezoelectric portion thickness” in the figure) increases in both pressure and displacement. In the range of the partition wall 2, when the thickness of the partition wall 2 is 100 μm, the pressure is approximately + 10% to −20%, and the displacement is approximately + 19% to −26%.
Therefore, from the viewpoint of ensuring a sufficient ink discharge pressure under the condition of a constant voltage, it is advantageous that the partition wall 2 is thin. However, there is a peak at 60 μm, and if the partition wall 2 is thinned beyond this, both pressure and displacement decrease. Therefore, the optimum thickness of the partition wall 2 is 60 μm under a constant voltage condition.

(2) “Laminated” type (the second base has a single layer structure) (see FIG. 3)
As shown in FIG. 3, this example share mode ink head 1 in which the thickness of the partition wall 2 is set to any 12 points within the range of 40 to 130 μm is actually driven under the same conditions, and the displacement of the partition wall 2 and the ink ejection The pressure was examined, and the amount of change was displayed as a plus / minus% based on the case where the thickness of the partition wall 2 was 100 μm.

According to FIG. 3, when the electric field is constant, the ink discharge pressure increases as the thickness of the partition wall 2 (“piezoelectric portion thickness” in the figure) increases in both pressure and displacement. In the range of the partition wall 2, when the thickness of the partition wall 2 is 100 μm, the pressure is approximately in the range of −65% to + 13%, and the displacement is approximately in the range of −58% to + 10%.
Therefore, under the condition of a constant electric field, it is advantageous that the partition wall 2 is thicker from the viewpoint of ensuring a sufficient ink discharge pressure.

According to FIG. 3, when the voltage is constant, the ink discharge pressure decreases as the thickness of the partition wall 2 (“piezoelectric portion thickness” in the figure) increases in both pressure and displacement. In the range of the partition wall 2, if the partition wall 2 thickness is 100 μm, the pressure is approximately in the range of + 8% to −14%, and the displacement is approximately in the range of + 10% to −12%.
Therefore, from the viewpoint of ensuring a sufficient ink discharge pressure under the condition of a constant voltage, it is advantageous that the partition wall 2 is thin. However, there is a peak at 60 μm, and if the partition wall 2 is thinned beyond this, both pressure and displacement decrease. Therefore, the optimum thickness of the partition wall 2 is 60 μm under a constant voltage condition.

(3) “Laminated” type (second base is a two-layer structure) (see FIG. 4)
As shown in FIG. 4, the share mode ink head 1 in this example in which the thickness of the partition wall 2 is set to any 12 points within the range of 40 to 125 μm is actually driven under the same conditions, and the displacement of the partition wall 2 and the ink ejection The pressure was examined, and the amount of change was displayed as a plus / minus% based on the case where the thickness of the partition wall 2 was 100 μm.

According to FIG. 4, when the electric field is constant, the ink discharge pressure increases as the thickness of the partition wall 2 (“piezoelectric portion thickness” in the figure) increases in both pressure and displacement. In the range of the partition wall 2, when the partition wall 2 thickness is 100 μm, the pressure is approximately in the range of −68% to + 12%, and the displacement is approximately in the range of −58% to + 10%.
Therefore, under the condition of a constant electric field, it is advantageous that the partition wall 2 is thicker from the viewpoint of ensuring a sufficient ink discharge pressure.

According to FIG. 4, when the voltage is constant, the ink discharge pressure decreases as the thickness of the partition wall 2 (“piezoelectric portion thickness” in the figure) increases in both pressure and displacement. In the range of the partition wall 2, when the partition wall 2 thickness is 100 μm, the pressure is approximately in the range of + 5% to −18%, and the displacement is approximately in the range of + 16% to −12%.
Therefore, from the viewpoint of ensuring a sufficient ink discharge pressure under the condition of a constant voltage, it is advantageous that the partition wall 2 is thin. However, there is a peak at 60 μm, and if the partition wall 2 is thinned beyond this, both pressure and displacement decrease. Therefore, the optimum thickness of the partition wall 2 is 60 μm under a constant voltage condition.

  Table 1 shows the ratio of the generation pressure between the “no lamination” type and the “lamination” (second base 7 has a two-layer structure) type. When the pressure at the time of ejection from the ink ejection chamber 5 in the case of the “no lamination” type is 1, the total thickness of the second base 7 in the “lamination” (second base 7 is a two-layer structure) type is 5 As shown in Table 1, the pressure ratio in the case of ˜50 μm is 1.19 times to 1.12 times, and generally a pressure that is 20 to 10% higher than that of the “no lamination” type is obtained. . In the case of a laminated type, a higher pressure is obtained when the total thickness of the second base portion 7 is as thin as possible.

  As described above, according to the share mode ink head 1 of this example, not only the partition wall 2 of the ink discharge chamber 5 but also the base 3 on the bottom surface side is actively driven by applying voltage to the piezoelectric element, Since it is possible to increase the pressure generation efficiency in the ink discharge chamber 5 while suppressing excessive deformation of the partition wall 2 during ink discharge, the pressure in the ink discharge chamber 5 can be secured stably and sufficiently. It is possible to provide a share mode ink head 1 composed of a highly reliable lead-free piezoelectric material that can solve the problem of drop ejection force or lack of uniformity and lack of reliability and can perform high-quality printing over a long period of time. The effect is obtained.

It is sectional drawing of the share mode ink head of this example. It is a graph which shows the relationship between the thickness of the partition in the share mode ink head ("no lamination | stacking" type) of this example, a discharge pressure change, and a partition displacement change. It is a graph which shows the relationship between the thickness of the partition in the share mode ink head ("with lamination" 1 layer type) of this example, the discharge pressure change, and the partition displacement change. It is a graph which shows the relationship between the thickness of the partition in the share mode ink head (“with lamination” two-layer type) of this example, the discharge pressure change, and the partition displacement change.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Share mode ink head 2 Partition 3 Base 4 Lid 5 Ink discharge chamber 6 Common electrode 7 Second base 8 Individual electrode

Claims (5)

A plurality of partition walls made of piezoelectric material arranged at predetermined intervals, a base portion made of a piezoelectric material commonly provided on the bottom side of each partition wall, a lid provided on the upper side of each partition wall, and An electrode provided on an inner surface of an ink discharge chamber partitioned by a partition wall, the base portion, and the lid, and applying a predetermined voltage to the electrode causes a shear mode deformation of the partition wall. In the share mode ink head that discharges ink from the ink discharge chamber by changing the volume of the discharge chamber,
A share mode ink head, characterized in that a common electrode to which a voltage equivalent to a voltage applied to the electrode of the ink ejection chamber to which ink is to be ejected is constantly applied is provided on the lower surface of the base portion. . 2. The share mode ink head according to claim 1, wherein a second base portion made of a piezoelectric material is provided on a lower surface of the common electrode. 3. The share mode according to claim 1, wherein when the voltage applied to the electrode and the common electrode is constant, a thickness of the partition with respect to a direction of a potential due to the voltage is set to 60 to 80 μm. Ink head. 4. The share mode ink head according to claim 1, wherein the piezoelectric material is a piezoelectric material containing no lead component. 4. The share mode ink head according to claim 1, wherein the piezoelectric material is a piezoelectric material containing a lead component.