JP3125299B2 - Recording head for inkjet printer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording head for an ink jet printer that writes a recording image on a recording medium by flying ink droplets.

(Prior Art) A piezoelectric conversion member is disposed with a slight gap on the back surface of a substrate provided with nozzles, and a voltage is applied to the piezoelectric conversion member to displace the piezoelectric conversion member, thereby removing ink interposed between the substrate and the piezoelectric conversion member. An on-demand type ink jet printer which pressurizes the ink and discharges it from a nozzle is already disclosed in Japanese Patent Publication No. 60-8957.

An inkjet printer with such a structure is
Compared to a general inkjet printer that applies pressure to the ink in the ink chamber by the piezoelectric conversion member and ejects the ink from the nozzle, the piezoelectric conversion member is located near the nozzle and is displaced in the axial direction of the nozzle. Is adopted, the flow path of the ink can be shortened to increase the discharge efficiency and the discharge stability,
In addition, there is an advantage that even if bubbles and dust are mixed in the ink, the ink can be normally operated without being affected by these.

By the way, in such an ink-jet printer, the gap between the piezoelectric conversion member and the substrate plays a major factor in determining the ejection speed, the ejection amount, or the ejection response of the ink droplet. Because the piezoelectric element and the metal plate are configured as a laminate, warpage occurs due to the difference in the coefficient of thermal expansion between the two, and the gap between the substrate and the substrate cannot be kept constant. In addition, in addition to the problem that the print density changes depending on the temperature, it is extremely difficult to form the piezoelectric conversion member thinly, which limits the reduction in driving voltage or current consumption.

(Problems to be Solved by the Invention) The present invention has been made in view of such a problem, and an object of the present invention is to make a piezoelectric conversion member thinner and to provide a gap between the piezoelectric conversion member and a substrate. It is another object of the present invention to provide a new recording head for an ink jet printer that can maintain the image quality accurately and can be driven with a lower voltage.

(Means for Solving the Problems) In other words, in order to solve the problems, the present invention employs one of two members disposed opposite to each other with a minute gap for interposing ink to discharge ink droplets. A recording head for an ink-jet printer in which a member provided with a nozzle is formed, and the other member is formed of a piezoelectric material as a pressurizing member for the ink, wherein the ink pressurizing member has a surface on which ink positioned at the nozzle portion is disposed. The pair of positive and negative comb-shaped electrodes are polarized under an arrangement in which bending deformation in a direction in which a pressing force is applied occurs.

(Operation) With this configuration, when a voltage is applied to the pair of comb-shaped electrodes, the ink pressing member made of a piezoelectric material is directly curved and deformed, and the ink located between the two members is pressed. This can be ejected from a nozzle as an ink droplet onto a recording medium.

(Embodiment) Therefore, an embodiment illustrated below will be described.

FIG. 1 is an enlarged view of a main part of a recording head according to an embodiment of the present invention.

This recording head is applied to an ink jet printer as shown in FIG. 2, runs in the axial direction of the platen 4, and rotates the platen 4 in the direction of the arrow to record a required recording image on the surface of the recording paper 3. Is configured to be written.

The recording head 10 includes a nozzle plate 11 and a vibrator 14 made of a piezoelectric material. A plurality of nozzles are provided on a nozzle plate 11 from the upper left to the lower right in FIG.
12 are formed. The nozzle plate 11 is provided with gap plates 13, 13 having a thickness of 10 to 20 μm on both sides of the nozzle plate 11 so as to sandwich the nozzle 12, but these may be formed integrally with the nozzle plate 11.

The vibrator 14 is an ink pressurizing member that applies the ink flowing between the nozzle plate 11 and discharges the ink from the nozzle 12 onto the recording paper.
Are suspended on the left and right gap plates 13 so that a certain gap is formed between them. This vibrator 14
Each of the nozzles 12 is formed as a narrow plate having a width of, for example, 0.34 mm corresponding to the pitch of the nozzles 12 and a thickness of 100 μm so that the nozzles 12 can independently perform a deformation operation. These are individually bonded on the gap plates 13 and 13.A wide oscillator is bonded on the gap plates 13 and 13 and cut or cut by a dicing saw or photo-etched. It is also possible to separate them as narrow-width vibrators 14 corresponding to the nozzles 12.

In these vibrators 14, an electrode pattern in which a positive comb electrode 17 and a negative comb electrode 18 are engaged with each other is integrally formed on a surface 14a opposite to the nozzle plate 11, Each of the electrodes 17, 18 is connected to a power source.

These comb-shaped electrodes 17, 18 deform the vibrator 14 by the applied voltage, and the interval between the teeth of the comb-shaped electrodes 17, 18 is set to about 1/2 of the thickness of the vibrator 14. It is desirable.
These comb-shaped electrodes 17 and 18 are arranged such that the teeth of the two comb-shaped electrodes 17 and 18 in the central region Lc located immediately above the nozzle 12
Both end regions extending in the longitudinal direction and inside the portion supported by the gap plates 13, 13
In Ls, the teeth of both comb electrodes 17 and 18 are formed so as to extend in the width direction of the vibrator 14.

When a unidirectional pulse voltage is applied between the comb-shaped electrodes 17 and 18 formed in this way, in the central region Lc, as shown in FIG. Arrow E
Is generated, and accordingly, distortion is generated in the direction of arrow y parallel to the electric field and in the directions of arrows X and Z perpendicular to the electric field. Then, in the longitudinal direction of the vibrator 14 (arrow X
Focusing on the strain in the direction) and the strain in the width direction (arrow Z direction), since the electric field strength is stronger on the surface 14a on which the electrode pattern is formed, in the central region Lc of the vibrator 14, the surface 14a is in the longitudinal direction and the width direction. As a result, the vibrator 14 is curved so that the surface 14a on the opposite side to the nozzle plate 11 is inside, as shown in FIG. 3 (b). I do.

On the other hand, as shown in FIG. 4 (a), when an electric field in the direction of arrow E is generated between the two electrodes 17 and 18 in the regions Ls at both ends, the strain in the direction y parallel to the electric field also becomes perpendicular to the electric field. Distortions in the directions x and z occur. Focusing on the strain in the direction of the arrow y, the electric field strength is the surface 14 on which the electrodes 17 and 18 are formed.
a is stronger, so this surface 14a has a width direction (arrow X direction)
As a result, in the longitudinal direction (arrow Z direction), the longitudinal strain also appears large, and as a result, the vibrator 14 moves downward with the gap plate 13 as a fulcrum, as shown in FIG. I.e. the surface 14 opposite the nozzle plate 11
Curves and deforms so that a becomes convex.

For this reason, the vibrator 14 has the fifth effect by these two actions.
As shown in FIG. 6B, the surface is not located in the central region Lc.
In the region Ls at both ends, the surface 14a is formed so that 14a is concave.
As a result, the vibrator 14 is deformed so that
The ink interposed between the nozzle plate 11 and the nozzle plate 11 is pressurized and ejected from the nozzles 12 as ink droplets onto recording paper (not shown).

The maximum vibration frequency of the vibrator 14 is determined by the Young's modulus of the piezoelectric material and the dimensions of the vibrator 14 itself. According to experiments, ink could be ejected at a frequency of about 6 KHz.

Note that, in this embodiment, the comb-shaped electrodes 17, 18 having different directions in the central region Lc and the two end regions Ls of the vibrator 14, respectively.
Is formed, but the comb-shaped electrode is formed only in the central region Lc.
17 and 18 may be provided so that the vibrator 14 is bent in a required direction.

FIGS. 6, 8 and 9 show a further preferred embodiment of the present invention in which comb-shaped electrodes are formed on both surfaces to more effectively deform the vibrator.

In the embodiment shown in FIG. 6, similarly to the embodiment shown in FIG. 1, the vibrator 24 is fixed with the vibrator 24 suspended on the gap plates 23 provided on both sides of the nozzle plate 21. ing.

The upper surface 14a of the vibrator 24 opposite to the nozzle plate 21
As shown in FIG. 6 (a), a pair of comb-shaped electrodes 27a and 28a
The lower surface 24b facing the nozzle plate 21 is formed on the lower surface 24b facing the nozzle plate 21 as shown in FIG. 6 (b).
A pair of comb-shaped electrodes 27 connected at 7a, 28a and end 24c
b and 28b are formed. These comb electrodes 27b and 28b
Is opposite to the electrode pattern on the upper surface 24a,
28b are formed as patterns that engage with each other in the longitudinal direction at both ends of the vibrator 24.

When a voltage is applied between the two comb electrodes 27 and 28 thus formed, the comb electrodes 27a and 28a at the center of the upper surface 24a are connected to this surface 2a as already described with reference to FIG.
4a acts to shrink the central portion, and on the lower surface 24b, comb-shaped electrodes 27b and 28b provided at both ends are formed on this surface 24b.
Acts to shrink both ends of b. As a result, as shown in FIG. 7, the vibrator 24 is curved and deformed toward the nozzle 22 at the center thereof, pressurizes the ink in this portion, and discharges the ink from the nozzle 22 as ink droplets.

On the other hand, the embodiment shown in FIG.
7 and 38 are formed in such a manner that they are polarized in the width direction of the vibrator 34. That is, on the upper surface 34a of the vibrator 34 opposite to the nozzle plate 31, both comb-shaped electrodes 37a and 38a are formed at both ends, and the lower surface 34b facing the nozzle plate 31
In FIG. 8, as shown in FIG.
37a, 38a are formed at both ends, and on the lower surface 34b facing the nozzle plate, as shown in FIG. 3B, connected to the comb-shaped electrodes 37a, 37a on the upper surface 34 at the end 34c of the vibrator 34. Each of the comb electrodes 37b and 38b is formed in the center.

In this embodiment, as described in FIG.
, The comb-shaped electrodes 37a and 38a at both ends extend the surfaces 34a at both ends of the vibrator 34, and the lower comb-shaped electrodes 37b and 38b at the center of the vibrator 34 at the lower surface 34b. 34b
As a result, the vibrator 34 curves toward the nozzle 32.

FIG. 9 shows an embodiment in which the vibrator is of a cantilever type and comb electrodes are provided on both surfaces thereof.

Gap plate fixed to one side of nozzle plate 41
43 has a vibrator with the free end covering nozzle 42
The base end of 44 is fixed. In this vibrator 44, positive and negative pairs of comb-shaped electrodes 47a and 48a are formed on the upper surface 44a on the opposite side of the nozzle plate 41 so as to oppose each other in the width direction. As shown in FIG. 4B, the lower surface 44b of the
Comb electrodes 47b, 48b connected to the comb electrodes 47a, 48a of 4a
However, the teeth are formed so as to mesh with each other in the longitudinal direction of the vibrator 44.

In this embodiment, when a voltage is applied to both the comb electrodes 47 and 48, as shown in FIG. 10, both the comb electrodes 47 on the upper surface 44a side.
a, 48a act to extend this surface 44a,
The two comb electrodes 47b and 48b of 4b act to contract this surface 44b. As a result, the vibrator 44 bends so that the free end side approaches the nozzle 42, pressurizes the ink interposed between the vibrator 44 and the nozzle plate 41, and discharges the ink from the nozzle 42 as an ink droplet.

In this embodiment, the comb electrodes 47 and 48 are formed on both surfaces of the cantilever type vibrator 44.
Even if the comb-shaped electrodes 47 and 48 are formed only on the upper surface 44a opposite to the above, the same operation as described above can be caused.

On the other hand, in the embodiments shown in FIG. 11 and thereafter, a nozzle is formed on the vibrator itself to make the recording head simpler and thinner.

FIG. 11 shows the overall configuration of this embodiment. The recording head 50 is composed of a base 51 and an ink pressing member 55 fixed thereon.

The base 51 is formed as a plate-like block having an E-shaped cross section extending in the direction in which the nozzles 52 are arranged. On both sides of the base 51, ridges 51a, 51a for supporting the ink pressurizing member 55 are formed. A central portion of the ink pressurizing member 55 facing the nozzle 52 via 51b,
Gap forming base for forming a gap of about 10 μm
51c is integrally formed.

On the other hand, the ink pressurizing member 55 includes a plurality of vibrators 54 separated by slits 56, and each vibrator 54
The nozzle 54 is provided with a nozzle 52 at the center in the longitudinal direction.

As shown in FIG. 12 (a), these vibrators 54 include a positive comb-shaped electrode 57 connected to each signal electrode 54c on an upper surface 54a not in contact with ink, and a negative comb-shaped electrode connected to a common electrode 58c. Are formed. These comb electrodes 57,
Numeral 58 is formed so that one or a plurality of comb-shaped electrodes extending inward from both ends of the vibrator 54 are wrapped around the central portion Lc where the nozzle 52 is formed.

Reference numeral 59 in the figure denotes a seal made of a soft resin material attached to the upper surface of the ink pressurizing member 55 in order to prevent the ink from leaking from the slit 56.
A hole 59a is provided so as not to hinder the ejection of ink from the nozzle 52.

In this embodiment, when a voltage is applied between the common electrode 58c and the selected one or a plurality of signal electrodes 57c, the respective comb-shaped electrodes 57, 58 connected to the common electrode 58c, as shown in FIG.
The selected vibrator 54 is curved toward the gap forming base 51c, the pressure of the ink in that portion is increased, and the ink is ejected from the nozzle 52 on the vibrator 54 toward the recording paper.

FIG. 12 (b) shows another embodiment of the electrode pattern on the vibrator, and a positive comb shape is provided at both ends of the vibrator 64 except for the central portion Lc of the vibrator 64 where the nozzle 62 is located. electrode
67 and a negative comb-shaped electrode 68 are formed so as to face each other.

By the way, the embodiment shown in FIG. 11 is such that the vibrators 54 provided with the nozzles 52 are separated by the slits 56 so as to operate independently of each other. Using a single ink pressurizing member, only the selected nozzle forming portion can be deformed.

FIG. 14 shows an embodiment of the present invention, in which the ink pressing member 75 fixed to the supporting ridges 71a on both sides of the base 71 is formed of a plate made of a single piezoelectric material. here,
A plurality of nozzles 72 are formed along a gap forming base 71c at the center of the base 71, and the upper surface thereof does not come into contact with ink.
75a has a positive annular comb-shaped electrode 77 connected to each signal electrode 77c.
The negative annular comb-shaped electrode 78 connected to the common electrode 78c is formed concentrically so as to surround each nozzle 72.

Then, when a voltage is applied to the selected one or more signal electrodes 77c and the common electrode 78c, the two annular comb-shaped electrodes 77, 7
8, as shown in FIG. 8B, the area Lc surrounding the corresponding nozzle 72 is bent toward the gap forming base 71 c, the ink in that part is pressurized, and this is formed as an ink droplet from the nozzle 72. Discharge.

(Effects) As described above, according to the present invention, one of the members disposed opposite to each other with a small gap is formed of a piezoelectric material, and a pair of positive and negative comb-shaped electrodes is provided on the surface thereof. When applied, the ink is deformed in the direction in which the pressure is applied to the ink corresponding to the individual nozzles, so that the ink is deformed.
The pressurized body of the ink can be constituted by a single part, and the electrode can be formed only on one surface, so that the head itself can be constituted simpler and smaller, and the heat can be reduced. And the like, and the gap between the other member is always kept constant, thereby enabling uniform ejection of ink droplets and further improving print quality. Moreover, by adopting a configuration in which the piezoelectric material itself as the ink pressurizing body is deformed, it is possible to drive with a lower voltage and a smaller current, and the power required for recording and writing can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view of a typical recording head of the present invention in which main parts are disassembled, FIG. 2 is a diagram showing an example of an ink jet printer having this recording head, and FIG.
FIG. 4B is a diagram showing a state before and after deformation occurring at a central portion of the diaphragm, and FIGS. 4A and 4B are diagrams showing a state before and after deformation occurring at both ends of the diaphragm. FIGS. 5 (a) and 5 (b) are diagrams showing an ink discharging operation by the diaphragm, and FIG. 6 (a) is a diagram showing a main part of a recording head according to a second embodiment of the present invention. FIG. 7B is a diagram showing the back surface of the diaphragm, FIG. 7 is a diagram showing an ink discharge operation by the diaphragm, and FIG. 8A is a third embodiment of the present invention. FIG. 9B is a diagram showing a main part of the recording head. FIG. 9B is a diagram showing the back surface of the diaphragm, and FIG. (B) is a diagram showing the back surface of the diaphragm, FIG. 10 is a diagram showing the ink ejection operation by the diaphragm, and FIG. 11 is an exploded view of the present invention. No. FIG. 12 (a) and (b) are views showing respective electrode patterns formed on the diaphragm, and FIG. 13 is an ink discharging operation by the diaphragm. Fig. 14 (a)
FIG. 9B is a diagram illustrating a recording head according to still another embodiment of the present invention and an ink discharging operation thereof. 11, 21, 31, 41 ... Nozzle plate 13, 23, 43 ... Gap plate 14, 24, 34, 44 ... Vibrator 17, 27, 37, 47, 18, 28, 38, 48 ... Comb type Electrodes 51, 71 ... Base, 52, 72 ... Nozzles 54, 64 ... Vibrators 55, 75 ... Ink pressing members 57, 67, 77, 58, 68, 78 ... Comb electrodes

Continued on front page (31) Priority claim number Japanese Patent Application No. 1-234894 (32) Priority date September 11, 1999 (September 11, 1989) (33) Country claiming priority Japan (JP) (31) Priority claim number Japanese Patent Application No. 1-241154 (32) Priority date September 18, 2001 (September 18, 1989) (33) Priority claiming country Japan (JP) (58) Field surveyed (Int.Cl) . ^7, DB name) B41J 2/045 B41J 2/055

Claims (2)

(57) [Claims] 1. One of two members opposed to each other in a minute gap for interposing ink is a member provided with a nozzle for discharging ink droplets, and the other member is pressurized by a piezoelectric material to pressurize the ink. In a recording head for an ink-jet printer formed as a member, the surface of the ink pressurizing member may be arranged so as to cause bending deformation in a direction in which a pressure is applied to ink in a portion corresponding to each of the nozzles. A recording head for an ink jet printer, wherein a pair of positive and negative comb-shaped electrodes are formed by polarization. 2. An ink jet printer in which one of two members disposed opposite to each other in a minute gap through which ink is interposed is formed of a piezoelectric material as an ink pressurizing member having a nozzle for discharging ink droplets. In a recording head, a pair of positive and negative comb-shaped members are arranged on the surface of the pressure member so as to cause bending deformation in a direction in which a pressure is applied to ink in a portion corresponding to each of the nozzles. A recording head for an ink jet printer, wherein electrodes are formed by polarization.