JPH0825632A - Ink jet record head - Google Patents

Abstract

PURPOSE:To restrain vibration at a thin part of a vibrating plate after an ink is discharged, by distributing proportion ally compliance of the whole vibrating plate to a nozzle opening side and an ink supply opening side such that the compliance at both sides are substantially the same. CONSTITUTION:When discharging of ink is completed and a piezoelectric vibrator 8 contracts to,an original state, a pressure generating chamber 4 expands, so that an ink flows in the pressure generating chamber 4 from a common ink chamber 6 through an ink supply opening 5, and a preparation is made for generation of next ink drops. In this case, a mass body 20 is added to a thin part 10 and compliance at both sides of the pressure generating chamber 4 which sandwiches the piezoelectric vibrator 8 is adjusted so as to be substantially the same. Accordingly, an energy which is released at a nozzle opening side and an energy which is released at the ink supply opening side become the same in magnitude, so that reciprocal movements do not occur. As a result, high-frequency vibration which vibrates meniscus is not generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an ink supply port at one end,
The present invention relates to a structure of an ink jet recording head that expands and contracts a pressure generating chamber whose nozzle opening communicates with the other end by a piezoelectric vibrator to eject ink in the pressure generating chamber.

[0002]

2. Description of the Related Art As is well known, a so-called multi-nozzle type ink jet recording head in which a plurality of nozzle openings are arranged on one substrate is provided with a nozzle plate having a plurality of nozzle openings, a pressure generating chamber and ink. A spacer that partitions the supply flow path and a second plate that seals the other surface are stacked and fixed, and a pressure is generated in the pressure generating chamber by the piezoelectric vibrator, and this pressure is compliant with elasticity of the second plate and the like. By accumulating the pressure, the ink droplets are ejected while the energy is effectively used.

In order to improve the recording density of the recording head, the pitch of the nozzle opening row tends to be small, and the size of the pressure generating chamber must be reduced accordingly. With such miniaturization of the pressure generating chamber, in an ink jet recording head that relies on a piezoelectric vibrator as a pressure generating source, the amount of displacement of the piezoelectric vibrator can be increased, so that the piezoelectric vibrator expands and contracts in the longitudinal direction. A mode piezoelectric vibrator is convenient.

FIG. 7A shows an example of an ink jet type recording head using the piezoelectric vibrator of the vertical vibration mode as described above. The vibration plate B forming the pressure generating chamber A is Island part D that receives the pressure of the piezoelectric vibrator C
The thin-walled portions G and H are provided on the nozzle opening E and the ink supply port F side with the thin-walled portions G and H sandwiched therebetween to ensure the compliance required for ink ejection. With such a configuration, when the piezoelectric vibrator C expands for ink ejection as shown in FIG. 7B, the thin portions G and H are generated by the pressure of about 3 atm generated in the pressure generating chamber A. Ink droplets are ejected from the nozzle openings E while flexing outward and collecting energy. When the piezoelectric vibrator C contracts to its original state after the ink droplet ejection is completed, each thin portion G,
The elastic energy stored in H is released.
The thin portions G and H function as a volume, and the ink in the entire pressure generating chamber A functions as a mass. Therefore, the difference in energy between the thin portion G and the thin portion H causes a difference in the pressure generating chamber A. Elastic vibration is generated in the ink. This vibration becomes a pressure wave and propagates alternately between the thin-walled portions G and H at a period of about 10 −6 seconds between the thin-walled portions G and H to vibrate the thin-walled portions G and H (C, D). This vibration vibrates the meniscus of the nozzle opening E communicating with the pressure generating chamber A at high speed, ink mist is generated from the nozzle opening E to contaminate the recording paper, and in severe cases, bubbles are generated in the pressure generating chamber. There is a problem in that printing is impossible by pulling in.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to suppress vibration in a thin portion of a diaphragm after ink is ejected. A new ink jet recording head is provided.

[0006]

In order to solve such a problem, according to the present invention, a nozzle plate having a nozzle opening and a through hole for partitioning a pressure generating chamber, an ink supply port and a reservoir are formed. The spacer provided and a diaphragm having a thin portion for ensuring compliance at least on the nozzle opening side and the ink supply port side, and a diaphragm having an island portion formed in the central portion are laminated, and the island portion is formed. In an ink jet type recording head that compresses the pressure generating chamber by a piezoelectric vibrator to eject ink droplets from the nozzle opening via, the overall compliance of the vibrating plate is substantially equal between the nozzle opening side and the ink supply port side. It was apportioned to be the same.

[0007]

Since the compliances on both sides of the pressurizing point are balanced, the elastic energy accumulated in the diaphragm becomes uniform, the pressure energy does not move before and after the piezoelectric vibrator is sandwiched, and the meniscus after ink ejection is completed. High-speed vibration does not occur and ink mist is prevented from occurring.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments. 1 and 2 are respectively an assembly perspective view and a sectional view of an ink jet recording head showing an embodiment of the present invention, in which reference numeral 1 is a nozzle opening 2,
Nozzle plate 3 having holes 2, 2, ... Perforated, spacers for partitioning a space to be the pressure generating chamber 4, the ink supply port 5, and the reservoir 6, 7 is a vibration plate, and these members are laminated. It is joined.

FIG. 3 shows an embodiment of the vibrating plate 7 described above, in which a wide range is deformed in conformity with the expansion and contraction of the piezoelectric vibrator 8 which will be described later, in conformity with each pressure generating chamber 4. The island portion 9 having a relatively high rigidity and the thin wall portions 10 and 11 for sandwiching the island portion 9 for ensuring compliance required for ink ejection are formed on the nozzle opening side and the ink supply port side. Is fixed by abutting its tip on the island portion 9.

Returning to FIGS. 1 and 2 again, reference numeral 8 in the drawings denotes the above-described piezoelectric vibrator, and in this embodiment, a plurality of electrodes 12, 1
3 and the piezoelectric material 14 are laminated so as to extend in the direction of the arrow A in the drawing when a drive signal is applied, and are fixed to the base 16 via a fixing plate 15. These piezoelectric vibrators 8, 8, 8 ... Are configured as a piezoelectric vibration unit by fixing one row of nozzles having a numerical aperture greater than or equal to the fixed plate 15 at a fixed pitch. When the piezoelectric vibrators 8, 8,
.. are brought into contact with the island portions 9, 9, 9 ,.

The vibrating plate 7, the spacer 3 and the nozzle plate 1 are sequentially laminated on the upper surface of the base 16 to form a frame body 19.
Are integrally fixed to the base 16 and integrated into an ink jet recording head.

FIG. 4 is an enlarged sectional view showing the vicinity of the nozzle opening, the pressure generating chamber, and the common ink chamber of the above-mentioned ink jet type recording head.
The thin portion 1 on the nozzle opening side where compliance is increased when one of the thin portions, that is, the vibrating plate 7 in this embodiment, is formed by the mass body for compliance adjustment.
It is attached to make the compliance of the thin portion 10 on the nozzle opening side the same as that of the thin portion 11 on the ink supply port side, or about 20% lower. Techniques such as adhesives and brazing can be used to add such mass.

In this embodiment, when a drive signal is applied to the piezoelectric vibrator 8 and the piezoelectric vibrator 8 expands and displaces, the displacement is transmitted to the diaphragm 7 via the island portion 9 and the pressure generating chamber 4 is compressed. As a result, the thin portion 10 on the nozzle opening side
Ink droplets having an optimum shape, size, and speed are ejected from the nozzle openings 2 according to the total compliance of both the ink supply port side thin portion 11 and the ink supply port side thin portion 11. At this time,
Since a pressure of about 3 atm is usually generated in the pressure generating chamber 4, the thin-walled portions 10 and 11 expand to the outside, that is, to the piezoelectric vibrating element 8 side, respectively, as shown in FIG. An ink droplet is ejected by temporarily storing a part of the energy and then releasing the energy.

When the piezoelectric vibrator 8 contracts to its original state after the ink ejection is completed, the pressure generating chamber 4 expands, whereby the common ink chamber 6 moves from the common ink chamber 6 to the pressure generating chamber 4 via the ink supply port 5. Ink flows in and prepares for the next ink drop.

However, in the present invention, the thin portion 1
Since the mass body 20 is added to 0, the compliances on both sides of the pressure generating chamber 4 sandwiching the piezoelectric vibrator 8 are adjusted to be substantially the same, the energy released on the nozzle opening side and the ink Since the magnitude of the energy released from the supply port side is the same as that of the energy released from the supply port side, there is no mutual movement, and therefore high-frequency vibration that vibrates the meniscus does not occur.

The meniscus self-oscillates at a relatively low frequency of about 5 kHz to 10 kHz which is determined by the fluid characteristics of the pressure generating chamber 4. However, the movement of the meniscus caused by such fluid characteristics has extremely small energy. Does not lead to the generation of ink mist.

FIG. 5 is a diagram showing the correlation between the ratio of the compliance on the ink supply port side to the compliance on the nozzle opening side and the occurrence of ink mist while keeping the overall compliance of the pressure generating chamber constant. In the figure, the symbol ◯ indicates the case where ink mist is not generated, the symbol Δ indicates the case where ink mist is slightly generated, and the symbol x indicates the case where ink mist is surely generated. An arc-shaped curve connecting the symbols indicates that the compliance is constant.

As is clear from FIG. 5, the larger the overall compliance is, the lower the vibration frequency is, and when the compliance on the nozzle opening side is equal to or smaller than the compliance on the ink supply port side by about 20%, the ink mist is reduced. Can be prevented.

FIG. 6 shows concrete means for adjusting the sizes of the compliance on the nozzle opening side and the compliance on the ink supply channel side, respectively, to balance the compliance of the two regions sandwiching the pressurizing point. It is shown.

In the embodiment shown in FIG. 6A, the compliance is adjusted by changing the shape of the pressure generating chamber 4. In this embodiment, the pressure generating chamber 4 on the ink supply port side is adjusted.
The width is narrowed slightly to make the compliance of the thin portion 11 in the region substantially the same as the compliance of the thin portion 10 on the nozzle opening 2 side.

In the embodiment shown in FIG. 6B, the position of the island portion 9 is moved by ΔL toward the ink supply port 5 side having a large compliance, and the thin portion 10 on the nozzle opening 2 side is moved.
The compliance is large, and the compliance of the thin-walled portion 11 on the ink supply port 5 side is small to achieve balance.

In the embodiment shown in FIG. 6C, the contact position of the piezoelectric vibrator 8 is displaced from the center of the island portion 9 to the ink supply port 5 side having large compliance, and the nozzle opening 2 side and the ink supply port side are arranged. And the compliance of the thin portions 10 and 11 is balanced.

In the embodiment shown in FIG. 6D, the shape of the pressure generating chamber 4 in the longitudinal direction, that is, the direction in which the nozzle opening 2 and the ink supply port 5 are connected to the line perpendicular to the longitudinal direction is defined. The pressure generating chamber 4 and the island portion 9 are precisely manufactured by arranging them symmetrically and arranging the island portion 9 and the symmetry lines C1 and C2 of the piezoelectric vibrator 8 so as to coincide with the symmetry line. If so, no special adjustment is required, which is a very practical method.

Further, due to the layout of the islands and the piezoelectric vibrators, the compliance of this region can be lowered by forming the thin portion on the side where compliance is inevitably thicker.

[0025]

As described above, in the present invention, at least a nozzle plate having a nozzle opening, a spacer having a through hole for partitioning a pressure generating chamber, an ink supply port, and a reservoir are provided. A thin portion for ensuring compliance is formed on the nozzle opening side and the ink supply port side, and a vibration plate with an island portion formed in the center is laminated, and pressure is applied by the piezoelectric vibrator through the island portion. In an inkjet recording head that compresses a generation chamber and ejects ink droplets from a nozzle opening, the overall compliance of the diaphragm is proportionally divided so that the nozzle opening side and the ink supply port side are substantially the same. Therefore, while keeping the compliance of the entire diaphragm at an optimum value, it was accumulated in the thin-walled parts existing at different positions across the pressing point. To suppress vibration due to Nerugi amount of difference, generation of the ink mist, and further to prevent retraction of the bubble in the pressure generating chamber f.

[Brief description of drawings]

FIG. 1 is an assembled perspective view showing an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing the vicinity of a pressure generating chamber.

FIG. 3 is an enlarged perspective view showing a diaphragm of the same apparatus.

FIG. 4 is an enlarged view showing the vicinity of the pressure generating chamber according to an embodiment of the present invention.

FIG. 5 is a diagram showing the relationship between the ratio of compliance on the nozzle opening side and the ink supply port side, and the occurrence of ink mist.

6A to 6D are views showing another embodiment of the present invention.

7A to 7D are views showing a state in which a conventional ink jet recording head is stationary, a state in which a piezoelectric vibrator is extended, and a state in which a thin portion is vibrating, respectively. .

[Explanation of symbols]

 2 Nozzle opening 4 Pressure generating chamber 5 Ink supply port 6 Common ink chamber 7 Vibration plate 8 Piezoelectric vibrator 9 Island part 10, 11 Thin part 20 Mass body

Claims (5)

[Claims] 1. A nozzle plate having a nozzle opening, a spacer having a through hole for partitioning a pressure generating chamber, an ink supply port, and a reservoir, and a compliance at least on the nozzle opening side and the ink supply port side. And a vibration plate having an island portion formed in the center thereof are laminated, and the pressure generating chamber is compressed by a piezoelectric vibrator through the island portion and the nozzle opening is formed. In the ink jet recording head for ejecting ink droplets from the ink jet recording head, the compliance of the entire vibrating plate is proportionally divided so that the nozzle opening side and the ink supply port side are substantially the same. 2. A mass body is added to the thin portion on the nozzle opening side or the thin portion on the ink supply port side so that the compliance of the entire vibration plate is substantially the same on the nozzle opening side and the ink supply port side. The ink jet recording head according to claim 1, wherein the ink jet recording head is configured as described above. 3. The compliance of the whole diaphragm is supplied to the nozzle opening side and the ink supply side by displacing the island portion to the side having the larger compliance among the thin portion on the nozzle opening side or the thin portion on the ink supply port side. The ink jet recording head according to claim 1, wherein the ink jet recording head is configured to be substantially the same on the mouth side. 4. The compliance of the whole vibration plate is a nozzle by displacing the contact position of the piezoelectric vibrator to the side having a larger compliance among the thin portion on the nozzle opening side or the thin portion on the ink supply port side. 2. The ink jet recording head according to claim 1, wherein the opening side and the ink supply port side are configured to be substantially the same. 5. The pressure generating chamber and the piezoelectric vibrator,
And the island portion is formed so as to be substantially symmetrical with respect to a line perpendicular to the longitudinal axis of the island portion, and the island portions are arranged so as to coincide with each other.
Inkjet recording head.