JP3075582B2 - Inkjet head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art As a conventional piezoelectric ink jet printer head, a Kaiser that deforms a wall of a pressure chamber filled with ink by using the bending of a piezoelectric element by bimorph and discharges ink by a rise in the pressure of the pressure chamber at that time. The method is described in, for example, Japanese Patent Publication No. 57-20904.

Also, utilizing the deformation of the piezoelectric element in the shear mode, the partition wall of the channel filled with ink is deformed, and the ink is ejected by increasing the pressure of the channel at that time.
No. 1 publication.

[0004]

However, each of the above-mentioned conventional systems has a problem. In the Kaiser method, since the pressure chambers are arranged on a plane, the nozzle pitch is larger than the nozzle pitch of the multi-nozzles, and an ink flow path connected to the nozzles is required, which increases the resistance of ink ejection, causing pressure loss and increasing the size of the head Become.

In addition, in the shear mode, a groove is required to be formed by cutting a width of several tens of microns to form a pressure chamber and a partition wall, which leads to an increase in cost. In order to eject ink, the partition walls themselves are deformed in a shearing mode. However, since the partition walls are common to the adjacent pressure chambers, there is a problem that the pressure between adjacent pressure chambers interferes. Further, due to the structure, ink cannot be ejected from adjacent nozzles at the same time.
SUMMARY OF THE INVENTION An object of the present invention is to provide a low-cost, small-sized, high-performance ink jet head that can be easily processed and assembled.

[0006]

In order to solve the above problems, an ink jet head according to the present invention has an upper substrate, a lower substrate, and a pressure chamber opened in the thickness direction between the upper and lower substrates. A nozzle plate having a drive electrode on an intermediate surface, a plate-shaped piezoelectric body having opposite polarities above and below the intermediate surface and polarized in a thickness direction, and a nozzle plate having a nozzle hole coupled to the pressure chamber; and ink supply means. Wherein the volume of the pressure chamber is changed by changing the thickness direction of the plate-shaped piezoelectric body by applying a voltage to the drive electrode.

The ink jet head of the present invention has an upper substrate and a lower substrate, and a pressure chamber opened in the thickness direction between the upper and lower substrates. A plurality of plate-like piezoelectric bodies and partition walls, which are opposite to each other in polarity and are polarized in the thickness direction, are alternately stacked one on another, and are connected to the pressure chamber to have a nozzle plate having a nozzle hole; and ink supply means. The volume of the pressure chamber is changed by changing the thickness of the piezoelectric plate by applying a voltage to the drive electrode.

[0008]

According to the present invention, the pressure chambers are filled with ink from the ink supply means, and the pressure chambers for discharging the ink are pressurized by driving electrodes provided on both surfaces of the plate-shaped piezoelectric body and on the intermediate surface inside the plate-shaped piezoelectric material. By reducing the thickness of the plate-shaped piezoelectric body by applying a voltage to the pressure chamber to reduce the volume of the pressure chamber.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of an embodiment according to the present invention will be described below with reference to the drawings. FIG. 1 is an exploded perspective view of an ink jet head according to the present invention, and exemplifies a case of three nozzles for simplifying the description. Plate-like piezoelectric bodies 201, 202, 401, 402, 601, having electromechanical conversion characteristics;
602 is a pressure chamber 201c, 202c, 401c, 402
c, 601c and 602c are hollowed out so as to be opened in the thickness direction, and one end of each of the ink reservoirs 201d and 201c is cut out.
2d, 401d, 402d, 601d, and 602d are formed. Plate-shaped piezoelectric bodies 201, 202, 401, 40
2, 601 and 602 each form a pair of plate-like piezoelectric bodies 200, 400 and 600. That is, one of the plate-like piezoelectric members 201 of the set of plate-like piezoelectric members 200 includes:
The drive electrode 201a is provided only on one side (upper side), and the drive electrodes 202a, 202
b is arranged and pressed and fired to form a set of plate-shaped piezoelectric bodies 200. Hereinafter, a pair of plate-shaped piezoelectric bodies 400 and 6
00, drive electrodes 401a, 601a are arranged only on one side of one plate-shaped piezoelectric body 401, 601, and drive electrodes 402a, 40a are provided on both sides of the other plate-shaped piezoelectric body 402, 602.
2b, 602a and 602b are provided.

The partition plates 30, 50 are provided with ink reservoirs 30.
d and 50d are hollowed out so as to open in the thickness direction. A plurality of the plate-like piezoelectric bodies 200, 400, 600 and the partition plates 30, 50 are alternately stacked in order, and the ink reservoirs 201d, 202d, 30d, 401d, 40
2d, 50d, 601d, and 602d are stacked and arranged so as to correspond to each other to form a common ink reservoir, and are sandwiched between the upper substrate 80 and the lower substrate 70. The upper substrate 80 is provided with an ink supply hole 81. Now, when ink is supplied from the ink supply hole 81, the ink is stored in the ink reservoir 201.
d, 202d, 30d, 401d, 402d, 50d,
From 601d and 602d, pressure chamber 201c of
202c, 401c, 402c, 601c, and 602c. The other end of the pressure chamber is connected to the nozzle holes 10a, 10b, and 10c of the nozzle plate 10.

The periphery 201 of the plate-like piezoelectric members 201 and 202
, 202-2, 202-1 and 201-2 (hereinafter referred to as through-hole electrodes).
-1, 202-2, 202-3... Are provided, and the through-hole electrodes 30-1, 30-1
Are formed in advance. Similarly, the lower substrate 7
The through-hole electrodes 70-1 and 70-
2, 70-3,..., And a flexible wiring board 90 for leading out electrodes is provided outside the lower substrate 70, and the respective electrodes are led out through through-hole electrodes. That is, the upper drive electrode 201a of the plate-shaped piezoelectric member 201 is transferred to the through-hole electrode 202-1 of the lower plate-shaped piezoelectric member 202 via the through-hole electrode 201-1.
Are connected to the through-hole electrodes 30-1 provided in the lower layer, and the corresponding through-hole electrodes 401-1 and 402-1 in the lower layer are sequentially connected.
50-1, 601-1, 602-1... And finally the external lead electrode terminals 90 of the lowermost flexible wiring board 90 via the through-hole electrodes 70-1 of the lower substrate 70.
-1. Here, the drive electrode 201a of the plate-shaped piezoelectric body 201 is in contact with the through-hole electrode 201-1 and a drive electrode pattern is formed so as to avoid the other through-hole electrodes 201-2, 201-3,. . Similarly, the drive electrode pattern of the upper drive electrode 202a of the plate-like piezoelectric body 202 is formed so as to avoid the through-hole electrodes 202-1, 202-3,. To the external lead electrode terminal 90-2 of the flexible wiring board 90.

FIG. 2 is a partially assembled perspective view of FIG.
The nozzle plate 10 is a set of plate-like piezoelectric bodies 200, 400, 60
0 and the partition plates 30, 50, 70 are alternately stacked, and have nozzle holes 10a, 10b, 10c corresponding to the pressure chambers 200c, 400c, 600c.
Ink is supplied to each ink reservoir from an ink supply hole 81 provided in the ink reservoir.

FIG. 3 is a partially enlarged sectional view showing the deformed state of the pressure chamber for explaining the operating state of the ink jet head according to the present invention.
0, 400, and 600 on both surfaces, a double-sided drive electrode 201a,
202b, 401a, 402b, 601a, 602b
And intermediate surface drive electrodes 202a, 402a,
602a are provided, and a voltage is applied to the double-sided drive electrode and the intermediate-side drive electrode of the pair of plate-shaped piezoelectric bodies to generate an arrow 201.
j, 202j, 401j, 402j, 601j, 602
It is polarized in the j direction. That is, the polarities are opposite to each other above and below the intermediate surface drive electrode, and are polarized in the thickness direction. Therefore, when the drive electrodes are only on both sides, when the respective plate-shaped piezoelectric bodies are simultaneously polarized, the partition plate is also polarized, so that simultaneous polarization is impossible and mass productivity is difficult. By providing the intermediate plane driving electrode in the middle of the plate-shaped piezoelectric body, it is possible to perform simultaneous polarization using the common intermediate plane driving electrode during polarization, and to achieve mass production polarization. In addition, the plate-shaped piezoelectric body
Since the layer structure is adopted, the applied voltage can be reduced to す る に は to make the thickness displacement the same, which is efficient.

Now, when the two-sided drive electrodes 201a and 202b of a pair of plate-like piezoelectric members 200 are set to the ground level and the intermediate surface drive electrode 202a is set to a positive potential, the pair of plate-like piezoelectric members 20a
The thickness of 0 is displaced from the solid line 25 as shown by a dotted line 26, the volume of the pressure chamber 200c decreases, the pressure of the ink filled in the pressure chamber increases, and the ink passes through the nozzle hole 10a as shown in FIG. The droplets are discharged to the outside as 20 g.

A set of plate-like piezoelectric bodies 200, 400, 600
Are made of piezoelectric ceramic green sheets, and the drive electrodes are made by printing or the like. The partition plates 30, 50... Also use piezoelectric ceramic green sheets of the same material.
... is just a structural material and does not need to be polarized. After alternately stacking them, the upper substrate 80 and the lower substrate 70 are attached to both sides, and are pressurized and fired, and integrated to form a multi-nozzle ink jet head.

In this embodiment, a piezoelectric ceramic is used for the plate-shaped piezoelectric body. However, an organic polymer piezoelectric film may be used.

Next, the specifications of the embodiment will be described with reference to FIGS. 4 and 5 are a partial plan view and a side view in the vicinity of the pressure chamber. To increase the resolution of the ink jet printer, it is necessary to make the nozzle pitch of the multi-nozzle head dense. Generally, about 300 nozzles are used per inch. In this case, the nozzle pitch is about 84
μm, and the thickness D of the pair of plate-like piezoelectric members 200 and the partition plate 30 is about 42 μm. The material of the plate-shaped piezoelectric body 200 is PZT, and the piezoelectric constant d ₃₃ in the longitudinal mode (thickness direction).
Is d ₃₃ = 4 × 10 ⁻¹⁰ m / V. Therefore, a distance between the intermediate surface drive electrode 202a and the two-sided drive electrodes 201a and 202b of the pair of plate-like piezoelectric bodies 200 is one.
When 2.5V is applied, the change in thickness per sheet is 0.0
05 μm, and the amount of change δ in thickness becomes δ = 0.01 μm irrespective of the thickness of the plate-shaped piezoelectric body. Assuming that the width of the pressure chamber 20c is W and the length is L, the volume change δP of the pressure chamber is δP = δ × W × L. 0.5mm width Assuming that a length of 20mm δP = 1 × 10 ^- a ⁴ mm ^3. When the diameter of the ink droplets ejected from the nozzle holes 10e and 30 [mu] m, the volume Q of the droplet is ^{Q = 1.4 × 10 - 5 mm} 3 wherein the volume of the volumetric change δP and the ink droplets in the pressure chamber 20 Q ΔP / Q = 7, and it can be seen that even if a part of the ink flows backward to the ink reservoir 200d, the volume change of the pressure chamber is sufficient. The diameter of the nozzle hole 10a is preferably about 30 μm.

[0018]

As described above, according to the present invention, an efficient and inexpensive head having a small size, a small pressure loss and a low efficiency can be obtained as compared with the conventional Kaiser system. Also, compared with the shear mode system, there is no active deformation of the partition wall during driving, and therefore there is no pressure interference between adjacent pressure chambers, and simultaneous ink discharge from adjacent nozzles is possible. In addition, if a multi-piece process using a green sheet is adopted, a cutting head for forming a pressure chamber is not required, and a characteristic head can be obtained. Also, the two plate-shaped piezoelectric members are joined to form a set of plate-shaped piezoelectric members, and an intermediate plane driving electrode is provided therebetween, so that the driving voltage is reduced by 1 / compared to a single plate-shaped piezoelectric member. Since only 2 is required and simultaneous polarization is possible, mass-production polarization has become possible.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of an inkjet head according to an embodiment of the present invention.

FIG. 2 is a partially assembled perspective view of FIG.

FIG. 3 is a partially enlarged cross-sectional view showing a deformed state of a pressure chamber for explaining an operation state of the present invention.

FIG. 4 is a partial plan view in the vicinity of a pressure chamber for explaining the specifications of the present invention.

FIG. 5 is a partial side view in the vicinity of a pressure chamber for explaining the specifications of the present invention.

[Explanation of symbols]

10 Nozzle plate 10a, 10b, 10c Nozzle hole 200, 400, 600 A set of plate-like piezoelectric bodies 201a, 202b, 401a, 402b, 601a,
602b Double-sided drive electrode 202a, 402a, 602a Intermediate-surface drive electrode 200c, 400c, 600c Pressure chamber 30, 50 Partition plate 70 Lower substrate 80 Upper substrate 81 Ink supply hole

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-73348 (JP, A) JP-A-50-140227 (JP, A) JP-A-63-224961 (JP, A) (58) Investigation Field (Int.Cl. ⁷ , DB name) B41J 2/045

Claims (2)

(57) [Claims] 1. An upper substrate and a lower substrate, and between the upper and lower substrates,
It has a pressure chamber that opens in the thickness direction, and a drive electrode is arranged on both surfaces and an intermediate surface inside, and a plate-like piezoelectric body that is opposite in polarity above and below the intermediate surface and polarized in the thickness direction is arranged. A nozzle plate having a nozzle hole coupled to the chamber, and an ink supply unit, wherein the volume of the pressure chamber is changed by changing the thickness direction of the plate-shaped piezoelectric body by applying a voltage to the drive electrode. Characteristic inkjet head. 2. An upper substrate and a lower substrate, and between the upper and lower substrates,
It has a pressure chamber that opens in the thickness direction, and drive electrodes are arranged on both surfaces and the intermediate surface inside, and a plate-like piezoelectric body and a partition plate that are opposite in polarity above and below the intermediate surface and polarized in the thickness direction are alternately arranged. A nozzle plate having a nozzle hole connected to the pressure chamber, and an ink supply means, and applying a voltage to the drive electrode to change the thickness direction of the plate-shaped piezoelectric body. An ink jet head characterized by changing the volume of a pressure chamber.