JPH0825624A - Ink jet head - Google Patents

Abstract

PURPOSE:To print image of high quality which is high in density and stable. CONSTITUTION:A pressure plate 5 comprises a thickest layer part 6 to be connected to a piezoelectric element 12b, a thin layer part 8 provided at the outside of the thickest layer part 6, and a thick layer part 7 provided at the outside of the thin layer part 8. When the piezoelectric element is driven, the thickest layer part 6 drives the thin layer part 8 so as to change a volume of a liquid chamber 4. As the outside of the thin layer part 8 is being the thick layer part, even when the piezoelectric element, for example, the piezoelectric element 12b is driven, a free end of the upper face of the piezoelectric element 12b does not come into contact with the thick layer part 7, so that a pitch L between the piezoelectric elements can be highly dense to be contracted up to a position where the piezoelectric element 12b and the thick layer part 7 overlap.

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 using a piezoelectric element as an actuator of an on-demand type ink jet recording apparatus, in which the actuator moves a liquid chamber communicating with a nozzle. The present invention relates to the shape of a pressure plate that receives a volume change.

[0002]

2. Description of the Related Art An ink jet recording method, which is one of non-impact recording methods, abruptly pressurizes ink in an ink liquid chamber to eject ink droplets from a discharge port (nozzle) toward a recording paper, Various types of methods have been proposed, such as a method of using a heat generating resistor as an ink pressurizing means, a method of using a piezoelectric element, etc. Moreover, this ink jet recording method does not generate noise during recording in principle.
Since the process is very simple and has many features such as small size, high reliability, and easy achievement of durability, it is an extremely effective recording method.

An on-demand type ink jet head using a piezoelectric element as an actuator is, for example, PZ.
An actuator is a piezoelectric element having a laminated structure in which plate-shaped piezoelectric elements such as T (lead zirconate titanate) and electrode materials are alternately laminated. The displacement direction of the piezoelectric displacement of the actuator is determined according to whether the voltage applied to the piezoelectric element is the polarization direction or the direction opposite to the polarization. When the applied voltage is the same as the polarization direction, the piezoelectric constant is set to d. _{As 33} , a piezoelectric displacement that extends in proportion to the applied voltage occurs, and in the opposite direction, a piezoelectric displacement that extends in a direction perpendicular to the applied voltage occurs in proportion to the applied voltage with the piezoelectric constant d ₃₁ .

The piezoelectric displacement of such an actuator is
The pressure plate is displaced, the volume of the liquid chamber is changed through the displaced pressure plate, and ink is ejected from a nozzle communicating with the liquid chamber.

In the conventional pressure plate, an island-shaped protrusion smaller than the liquid chamber contacting the piezoelectric element is arranged on the pressure plate at a position corresponding to the liquid chamber, and the protrusion is connected to the liquid chamber through the protrusion. As shown in FIG. 5, the method of giving a volume change is such that the thickness of the portion in contact with the liquid chamber with respect to the pressure plate having a constant thickness becomes a thin layer except for the portion in contact with the piezoelectric element. There is a system that did.

FIG. 5 is a sectional view showing an essential part of an example of a conventional on-demand type ink jet head, and is a sectional view as seen from a direction perpendicular to piezoelectric elements 40a, 40b ... Arranged in rows. is there.

The ink jet head 30 has a nozzle 32.
And a liquid chamber plate 33 that is joined to the nozzle plate 31 and has a liquid chamber 34 that communicates with the nozzle 32 of the nozzle plate 3, and is joined to the liquid chamber plate 33 and has the same thickness (L ₁ ) Thick layer portions 36 and 37 and a thin layer portion 38 having a thickness (L ₃ )
A liquid chamber unit including a pressure plate 35 constituted by
An actuator unit having piezoelectric elements 40a, 40b ...
The liquid chamber unit I and the actuator unit II are joined so that the piezoelectric elements 40a, 40b ... And the corresponding thick layer portions 36 are in contact with each other.

The thin layer portion 38 is a thin plate having an area corresponding to the liquid chamber 34, and has a thick layer portion 36 in contact with the piezoelectric elements 40a, 40b ... In the center. When the piezoelectric elements 40a, ... Are driven, the thick layer portion 36 transmits the piezoelectric displacement of the piezoelectric elements 40a, ... To the thin layer portion 38 to change the volume of the liquid chamber 34 and eject ink from the nozzle 32.

[0009]

The pressure plate 35 of the conventional ink jet head 30 shown in FIG. 5 has a thin layer portion 38 having a width corresponding to the width of the liquid chamber 34 and a thick layer portion 36 having the same thickness.
Since the two piezoelectric elements 40a, 40b ... Are made to have a constant width, the distance between the piezoelectric elements 40a, 40b ... Is limited by the width of the thick layer portion 37. It was not possible to increase the resolution by reducing the distance between the elements 40a, 40b ...

Further, in order to increase the resolution, the piezoelectric element 4
If the width of the thick layer portion 37 is reduced by shortening the interval between 0a and 40b, displacement of the thin layer portion 38 causes so-called nozzle interference that affects the adjacent thin layer portions 38.
There was a limit to reducing the width of.

The present invention has been made in view of the above-mentioned problems, and eliminates interference generated between nozzles of an ink jet head, enhances ink ejection efficiency with high rigidity, and is an on-demand type having stable and high resolution. It is an object to provide an inkjet head.

[0012]

In order to solve the above-mentioned problems, the present invention provides (1) a nozzle plate having a plurality of nozzles, and a plurality of liquids corresponding to each of the nozzles and communicating with the nozzles. An actuator that has a liquid chamber plate having a chamber, a pressure plate that changes the volume of the liquid chamber, and piezoelectric elements arranged corresponding to the liquid chamber, and that displaces the pressure plate by driving the piezoelectric element. In an inkjet head including a unit, the pressure plate is arranged corresponding to each of the liquid chambers, and a thin layer portion that changes the volume of the liquid chamber in response to the deformation of the piezoelectric element, and the thin layer portion. A thick layer portion disposed on the outer periphery and a thickest layer portion bonded to the piezoelectric element and disposed in the central portion of the thin layer portion; and (2)
The thickness difference between the thick layer portion and the thickest layer portion of the pressure plate is made larger than the deformation amount of the piezoelectric element, and further, (3)
The actuator unit is composed of a substrate, the plurality of piezoelectric elements fixed to the substrate, and a case that is a frame surrounding the plurality of piezoelectric elements and fixed to the substrate,
The thickness of the outer peripheral portion of the pressure plate joined to the case of the actuator unit is set to the thickness of the thickest layer portion, and (4) the piezoelectric elements arranged at both ends of the actuator are piezoelectric. A non-driven column that is not driven, and the non-driven column is joined to the outer peripheral portion of the pressure plate;
(5) The nozzle, the liquid chamber, and the pressure plate pressing unit are arranged in a staggered arrangement in the arrangement direction of the piezoelectric elements arranged in the actuator unit.

[0013]

The pressure plate of an on-demand type ink jet head using a piezoelectric element as an actuator has a three-layer structure of a thickest layer portion, a thin film portion and a thick layer portion having different thicknesses. The portion that gives the piezoelectric displacement to the surrounding thin layer portion is set as the thickest layer portion so that the free end of the piezoelectric element does not contact the thick layer portion around the thin layer portion. As a result, the pitch between the piezoelectric elements can be reduced to reduce the nozzle spacing to improve the printing resolution, and the rigidity of the assembly structure can be increased to increase the ink ejection efficiency, enabling stable high-resolution printing.

[0014]

【Example】

Example 1 (corresponding to claim 1) FIG. 1 is a partial perspective sectional view for explaining an inkjet head of Example 1, in which 1 is a nozzle plate, 2 is a nozzle, 3 is a liquid chamber plate, 4 is a liquid chamber, 5 is a pressure plate, 6 is the thickest layer portion, 7 is a thick layer portion, 8 is a thin layer portion, I is a liquid chamber unit, II
Is an actuator unit, 10 is a substrate, 11 is a case (frame), and 12a, 12b, 12c ... Are laminated piezoelectric elements.

In the on-demand type ink jet head shown in FIG. 1, a liquid chamber unit I in which a nozzle plate 1, a liquid chamber plate 3 and a pressure plate 5 are integrally bonded, and a plurality of piezoelectric elements are arranged at predetermined intervals L on a substrate. 10 and these piezoelectric elements 12
The actuator unit II includes a frame-shaped case 11 surrounding a, 12b, ...

The nozzle plate 1 is provided with a plurality of nozzles 2 formed at intervals L, and the liquid chamber plate 3 is formed at each interval L with liquid chambers 4 communicating with the nozzles 2. The pressurizing plate 5 has a flat joint surface with the liquid chamber plate 3, but has the thickest layer portion 6 on the non-joint surface on the YY line connecting the centers of the nozzle 2 and the liquid chamber 4.
However, a thin layer portion 8 having a width substantially equal to the width of the liquid chamber 4 is provided adjacent to the thickest layer portion 6, and further outside the thin layer portion 8 is thinner than the thickest layer portion. A thick layer portion 7 thicker than the thin layer portion 8 is provided to form a three-layer structure.

2 and 3 are views for explaining the details of the actuator unit in FIG. 1. FIG. 2 is an actuator unit in which the polarization direction of the piezoelectric element is d33, and FIG. 3 is in which the polarization direction of the piezoelectric element is d31. In the figure, 13 is a substrate common electrode, 14 is a substrate individual electrode, 15,
16 is a PZT end face electrode, 17 is a conductive paste, 12
a, 12b, ... 12n and 18a, 18b ,.
Reference numeral n denotes a piezoelectric element, and portions having the same functions as those in FIG. 1 are denoted by the same reference numerals as those in FIG. In addition,
In order to avoid complication, the illustration of the case 11 is omitted.

The actuator unit shown in FIG.
It has an actuator composed of stacked piezoelectric elements 12a, 12b, ..., 12n fixed on the substrate 9 and having a piezoelectric displacement in the direction d ₃₃ . Piezoelectric elements 12a, 12b,
.., 12n are arranged on the side end face in the arrangement direction, PZT
The end surface electrode 15 and the PZT end surface electrode 16 are formed in a pattern, and the electrodes arranged in the stacked individual elements are alternately connected to the respective PZT end surface electrodes 15 and 16.

The substrate 10 has a rectangular shape, and a substrate common electrode 13 having a common electrode 13a separated by a central portion 10a and a substrate individual electrode 14 are patterned on the upper surface in the longitudinal direction.
The substrate common electrode 13 and the PZT end face electrode 16 and the substrate individual electrode 14 and the PZT end face electrode 15 are joined with a conductive paste 17.

The substrate individual electrode 14 is formed on the substrate 10 by the groove 1
, 0n, and each piezoelectric element 12a, 12b, ..., 12n is disposed through the groove 10b so that each piezoelectric element is independently driven to cause piezoelectric displacement in the stacking direction (arrow F). It has become.

Like the actuator unit shown in FIG. 2, the actuator unit shown in FIG. 3 has a structure in which the piezoelectric elements 18a, 18b, ..., 18n are fixed on the substrate 10, but the piezoelectric elements 18a, 18b. , ..., 18n
Indicates that the piezoelectric displacement is in the d ₃₁ direction. Therefore, the element is displaced in the direction indicated by arrow F as in the case of FIG.
The direction is perpendicular to the 0 plane.

In FIG. 1, a liquid chamber unit I including a nozzle plate 1, a liquid chamber plate 3 and a pressure plate 5 and an actuator unit II are fixed on a substrate 10 so as to surround the piezoelectric elements 12a, 12b, .... The case 11 is joined together.

When the ink jet head shown in FIG. 1 is driven, for example, when a voltage is applied to the piezoelectric element 12b,
Piezoelectric displacement occurs in the piezoelectric element 12b in the extending direction, and the thickest layer portion 6 is pushed upward accordingly. The thin layer portion 8 is deformed by pushing up the outermost layer portion 6 and causes a change in volume of the liquid chamber 4. Due to this volume change, the ink in the liquid chamber 4 jumps out of the nozzle 2 and becomes an ink droplet, which rides on the recording paper and printing is performed. Ink is supplied to the liquid chamber 4 from a common liquid chamber (not shown).

As described above, the thickest layer portion 6 is formed on the pressure plate 5.
Since the thin layer portion 8 is provided around the thickest layer portion 6 and the thick layer portion 7 is provided outside the thin layer portion 8, the piezoelectric element 12b has a free end There is no contact with the thick layer portion 7, and the distance between the piezoelectric elements 12b and 12c can be reduced by that amount, high-resolution recording is possible, and the thickness between the adjacent liquid chambers 4 is increased. Since the layer portion 7 is provided, there is no interference between nozzles and high quality printing is possible.

However, if the piezoelectric deformation amount is larger than the difference in thickness between the thickest layer portion 6 and the thickest layer portion 7, the piezoelectric elements 12b,
When driving 12c, the piezoelectric elements 12b, 12c ,.
It is not possible to reduce the arrangement interval of the piezoelectric elements 12b, 12c, ... To the extent that the thick layers 7 are overlapped with 2b, 12c ,.

Embodiment 2 (corresponding to claim 2) The above interference makes the difference in thickness between the thickest layer portion 6 and the thickest layer portion 7 larger than the amount of deformation of the piezoelectric elements 12b, 12c, ... It can be solved.

As a result, the distance between the piezoelectric elements 12b, 12c, ... Can be reduced to such an extent that the piezoelectric elements 12b, 12c ,. It is possible to increase the density.

In order to increase the density of the ink jet head to improve the efficiency of ink ejection and to obtain stable high image quality, it is necessary to increase the rigidity of the ink jet head. The portions other than the thin layer portion 8 are deformed, and the ink ejection efficiency cannot be increased, so that stable high image quality cannot be obtained.

Example 3 (corresponding to claim 3) One means for increasing the rigidity of the ink jet head is to make the outermost part of the pressure plate 5 joined to the case 11 the thickest layer part 6. The case 11 and the pressure plate 5 are joined with high rigidity, and as a result, the rigidity of the entire inkjet head is increased.

Embodiment 4 (corresponding to claim 4) Another means for increasing the rigidity of the ink jet head is a piezoelectric element at both ends close to the case 11 of the actuator unit, for example, the piezoelectric element 12 in FIG.
a is a non-driving piezoelectric element and is simply a non-driving column, and the case 11 and the piezoelectric element 12a are joined at the thickest layer portion 6 on the outer peripheral portion of the pressure plate 5.

As described above, by joining the case 11 and the non-driving piezoelectric element 12a at the thickest layer portion 6 on the outer periphery of the pressure plate 5, the pressure plate 5 has higher rigidity and is deformed. Therefore, the ink ejection efficiency is high, and stable high-quality printing can be performed.

If the distance between the adjacent liquid chambers 4 is reduced in order to increase the density of the ink jet head, the adjacent liquid chambers 4 are interfered with each other by the driving of the piezoelectric element 12, which causes interference. There is a limit on the spacing between, and therefore, a limit for densification. Example 5 is made to raise the limit of high density.

Embodiment 5 (corresponding to claim 5) FIG. 4 is a view for explaining another embodiment of the ink jet head according to the present invention. In the figure, 21 is a nozzle plate, 22a, 22b, ... Are nozzles, 23 is a liquid chamber plate, 24
a, 24b, ... are liquid chambers, 25 is a pressure plate, 26 is the thickest layer, 27 is the thickest layer, and 28 is the thinnest layer. The same reference numerals as in FIG. 1 are attached.

The hydraulic unit I consisting of the nozzle plate 21, the liquid chamber plate 23 and the pressure plate 25 shown in FIG. 4 has a hydraulic pressure consisting of the nozzle plate 1, the liquid chamber plate 3 and the pressure plate 5 shown in FIG. It has the same action as the unit I, and each is a liquid chamber unit part integrally joined, but the nozzle plate 21 has
The nozzles 22a, 22b, 22c, ..., 22f, ... Are sequentially arranged in a zigzag pattern at intervals D according to the arrangement direction of the piezoelectric elements 12a12b ,.

The liquid chamber plate 23 has nozzles 22a, 22b,
, 22f, ... Corresponding to the liquid chambers 24a, 24b ,.
24f, ..., and the thickest layer portion 26a ,.
are arranged. Therefore, the piezoelectric elements 12b, 12 for contacting the thickest layer portion 26a and transmitting the piezoelectric displacement.
The contact positions of c ... Are points P ₁ , P ₂ ... In the figure, which are alternately arranged in a staggered manner with a distance D therebetween.

According to the ink jet head according to the fifth embodiment shown in FIG. 4, the liquid chambers 24a, 24b,
, 24f, ... are alternately arranged in a staggered manner, the distance between adjacent liquid chambers, for example, the liquid chambers 24a and 24b, becomes large, and the liquid chambers 24a and 24c in the same row have twice the liquid chambers. It becomes an interval. As a result, mutual interference does not occur and high-density and high-quality printing is possible.

[0037]

As is apparent from the above description, the present invention has the following effects. (1) Effect corresponding to claim 1: Since the pressure plate is composed of three layers, a thin layer, a thick layer, and a thickest layer, interference between the piezoelectric element and the thick layer portion on the outer periphery of the thin layer portion interferes with each other. Can be avoided. As a result, it is possible to reduce the pitch between the liquid chambers, and it is possible to increase the density of the inkjet head. (2) Effect corresponding to claim 2: Since the thickness difference between the thick layer portion of the thin plate outer peripheral portion of the pressure plate and the thickest layer portion joined to the piezoelectric element is set to be larger than the deformation amount of the piezoelectric element. The pitch between the liquid chambers can be reduced until the upper surface of the piezoelectric element and the thick layer portion overlap each other, and the density of the head can be increased. (3) Effect corresponding to claim 3: Since the thickness of the outer peripheral portion of the pressure plate joined to the case of the actuator unit is the thickest layer, the rigidity of the pressure plate and the entire head can be increased, and ink ejection High efficiency can be measured. (4) Effect corresponding to claim 4: Since the piezoelectric elements at both ends of the actuator are non-driven pillars that are not driven, and the thickness of the outer peripheral portion of the pressure plate joined to these non-driven pillars is the thickest layer,
The rigidity of the pressure plate and the rigidity of the entire head can be increased, and the efficiency of ink ejection can be improved. (5) Effect corresponding to claim 5: Since the pressure plate pressing portion, the liquid chambers, and the nozzles are arranged in a staggered arrangement with respect to the piezoelectric element array of the actuator unit, the pitch between the adjacent liquid chambers can be reduced, Higher density of inkjet head can be achieved.

[Brief description of drawings]

FIG. 1 is a perspective sectional view illustrating an inkjet head according to a first exemplary embodiment.

FIG. 2 is an actuator unit-1 for explaining details of the actuator unit in FIG.

FIG. 3 is a partial perspective view of each actuator unit-2.

FIG. 4 is a diagram for explaining another embodiment of the inkjet head according to the present invention.

FIG. 5 is a diagram showing an example of a main-portion cross-sectional view of a conventional on-demand type inkjet head.

[Explanation of symbols]

1 ... Nozzle plate, 2 ... Nozzle, 3 ... Liquid chamber plate, 4 ... Liquid chamber, 5
... pressure plate, 6 ... thickest layer part, 7 ... thick layer part, 8 ... thin layer part, I
… Liquid chamber unit, II… Actuator unit, 10
... substrate, 11 ... case (frame), 12a, 12b,
... 12n ... Piezoelectric element, 13 ... Substrate common electrode, 14 ... Substrate individual electrode, 15 ... PZT end face electrode, 17 ... Conductive paste, 18a, 18b, ... 18n ... Piezoelectric element, 21 ... Nozzle plate, 22a, 22b ... Nozzle, 23 ... Liquid chamber plate, 24
a, 24b ... liquid chamber, 25 ... pressure plate, 26 ... thickest layer part,
27 ... Thick layer portion, 28 ... Thin layer portion.

Claims (5)

[Claims] 1. A nozzle plate having a plurality of nozzles, a liquid chamber plate having a plurality of liquid chambers corresponding to each of the nozzles and communicating with the nozzles, and a pressure plate for changing the volume of the liquid chambers. In an inkjet head including an actuator unit having piezoelectric elements arranged corresponding to the liquid chambers and driving the piezoelectric elements to displace the pressure plates, the pressure plates correspond to the respective liquid chambers. And a thin layer portion that changes the volume of the liquid chamber in response to the deformation of the piezoelectric element, a thick layer portion that is disposed on the outer periphery of the thin layer portion, and that is bonded to the piezoelectric element. An ink jet head comprising a thickest layer portion arranged in the central portion of the thin layer portion. 2. The ink jet head according to claim 1, wherein the difference in thickness between the thickest layer portion and the thickest layer portion of the pressure plate is larger than the amount of deformation of the piezoelectric element. 3. The actuator unit includes a substrate, the plurality of piezoelectric elements fixed to the substrate, and a frame body surrounding the plurality of piezoelectric elements, the case fixed to the substrate, The ink jet head according to claim 1, wherein the thickness of the outer peripheral portion of the pressure plate joined to the case of the actuator unit is the thickness of the thickest layer portion. 4. The ink jet recording apparatus according to claim 3, wherein the piezoelectric elements arranged at both ends of the actuator are non-driving pillars that are not piezoelectrically driven, and the non-driving pillars are joined to an outer peripheral portion of the pressure plate. head. 5. The structure in which the nozzles, the liquid chambers, and the pressurizing plate pressurizing section are arranged in a zigzag manner in the arrangement direction of the piezoelectric elements arranged in the actuator unit. The described inkjet head.