JPH0224223B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ink-on-demand type inkjet, and particularly to a multi-nozzle head that integrates a large number of nozzles.

The ink-on-demand type inkjet has a simple structure and is expected to be suitable for various terminal printers, but its response speed is relatively low, so a multi-nozzle head that integrates a large number of nozzles to solve this problem has been developed. Proposed.

FIG. 1 shows a head 1 of this type, in which ink is supplied from an ink container (not shown) to a nozzle 2 through a supply port 3, a supply path 4, a pressurizing chamber 5, and a flow path 6. Head 1 forming the supply path
A piezoelectric element 7 of the pressurizing chamber 5 is disposed, and by applying a drive signal to the piezoelectric element 7, the volume of the pressurizing chamber 5 is changed, and ink droplets 8 are ejected from the nozzle 2 to perform printing. It is composed of

However, as devices become smaller, there is an increasing need to make heads smaller as well. Therefore, pressurization chamber 5
The distance B between them also becomes smaller. As a result, when a signal is applied to a certain piezoelectric element 7, the vibration is transmitted to the outer wall of the adjacent pressurizing chamber 5. As a result, fluctuations in the ink in the pressurizing chamber occur even in nozzles near the nozzle to be ejected, causing problems such as ink flowing out from the nozzle, wetting the end face of the nozzle, making ink ejection unstable, and causing air bubbles to be sucked in from the nozzle.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a new ink jet head that can eliminate instability in ink ejection caused by mutual interference between pressure chambers of an integrated multi-nozzle head.

FIG. 2 shows an embodiment of the present invention. This figure shows a cross section of the pressurizing chamber perpendicular to the ink flow direction.

11 is a white glass substrate with a pressure chamber 5 on its surface.
Ink channels such as these are formed by etching, surface pressing, etc. A diaphragm 12 is made of the same material as the substrate 11 and is thermally welded to the substrate 11. Groove 13 during welding
Instead, the diaphragm 12 is a flat plate. A piezoelectric element 14 is bonded to the diaphragm 12. When bonding, the piezoelectric element 14 is not divided into individual pieces corresponding to the respective pressurizing chambers, but is bonded in the form of a large flat plate. The thus laminated piezoelectric element 14 and diaphragm 12 are cut using a diamond wheel, and the thickness of the diaphragm 12 is reduced to 1/2 at the boundary between each pressurizing chamber.
This is a head formed by forming a groove 13 as shown in FIG.

Generally, when bending a flat plate, the same force causes a deflection that is inversely proportional to the cube of the plate thickness. Therefore, the effect on the adjacent pressurized chamber is 3 times the thickness of the plate for the same displacement.
It is considered to be approximately proportional to the power of Therefore, by making grooves up to half the thickness of the diaphragm 12, the effect can be reduced to 1/8 of that of a diaphragm without grooves, so each pressurization chamber can be placed close to each other, and the vibration system The drive voltage can be lowered by reducing the stiffness of the

In this embodiment, an example has been described in which the diaphragm and the piezoelectric element are cut and grooved at the same time after lamination. If you do this, the arrangement pitch of the pressurized chambers will be 250μ,
It is also possible to manufacture multi-nozzles that integrate approximately 1000 pressure chambers and nozzles at a density of 4 nozzles/mm. In such highly integrated heads with extremely fine array pitches, it is almost impossible to bond as many as 1000 piezoelectric elements with a width of approximately 200μ to the diaphragm due to the strength of the piezoelectric elements. 10 piezoelectric elements
It is quite possible to glue a sheet onto a diaphragm and divide it into 100 pieces each. Furthermore, when the pressurized chambers are arranged in a small pitch such as 250μ pitch, the stiffness is inversely proportional to the fourth power of the width of the diaphragm, so the diaphragm 12,
Although there is a problem that the rigidity of the vibration system consisting of the piezoelectric element 14 becomes extremely high and the driving voltage becomes high, according to this embodiment, the piezoelectric element and the diaphragm can be approximately regarded as a beam supported at both ends. Compared to a beam with both ends fixed, the deformation volume is six times greater for the same uniformly distributed load, and the driving voltage can be lowered accordingly. When the width of the pressurizing chamber is small in this way, by creating a groove, the rigidity of the vibration system is reduced and the driving voltage can be lowered.

FIG. 3 shows another embodiment of the invention. Reference numeral 21 denotes a substrate on which channels such as pressure chambers 5 are formed on the surface by injection molding of thermoplastic resin, and 22 is a diaphragm on which grooves 23 are formed on the surface by injection molding, unlike the example shown in FIG. A groove 23 is also formed in front of the substrate 21 at a position away from a joint 26 corresponding to a partition wall 25 forming a flow path. The substrate 21 and the diaphragm 22 are bonded together by applying a thin layer of dove cement to their bonding surfaces, and then being pressure-bonded using a jig.

After bonding the substrate 21 and the diaphragm 22, the piezoelectric elements 24 are bonded to each pressure chamber 5 individually. Note that since the groove 23 is arranged at a position away from the joint part 26, even if pressure is applied with a planar jig, the pressing force is applied directly to the joint part, increasing the reliability of the joint between the diaphragm and the substrate.

In the embodiment shown in FIG. 3, the head can be made by molding inexpensive plastic, and the diaphragm can be grooved without increasing the number of steps. Therefore, it is suitable for low-cost small serial printers. Note that it is also possible to form the channels and grooves by surface pressing, etc. other than injection molding.

Although each of the embodiments described above uses strip-shaped piezoelectric elements, mutual interference can also be avoided by creating grooves between each piezoelectric element in heads using piezoelectric elements in the shape of discs, square plates, etc. can be made smaller.

Further, in each of the illustrated embodiments, the flow path is formed on the substrate side, but the flow path may be formed on the diaphragm side, or a spacer may be placed between the substrate and the diaphragm to increase the flow rate. Even if a channel is formed, the effects of the present invention are the same.

As can be seen from the above embodiments, in the multi-nozzle head, by forming grooves between adjacent diaphragms of the diaphragms corresponding to each pressurizing chamber, vibration interference between each pressurizing chamber can be reduced. It is possible to eliminate wetting of the front surface of the nozzle due to ink outflow, increase the stability of ink ejection, and prevent air bubbles from entering the nozzle. Furthermore, since the pressurizing chambers can be placed close to each other, the entire head can be made smaller.

Particularly in the case of a high-density head, mass productivity can be increased by forming grooves after laminating the diaphragm and piezoelectric element. Furthermore, it also has the advantage that the drive voltage can be lowered by reducing the rigidity of the vibration system.

It is also possible to manufacture a low-cost head using plastic injection molding.In this case, by forming a groove in front of the joint at a position away from the joint, a multi-layer head is used to reduce vibration interference between each pressurizing chamber. Nozzle heads can be manufactured at low cost.

The present invention applies to printers, plotters, facsimiles,
It can be applied to various printing devices such as copying machines. As described above, according to the present invention, the piezoelectric element is completely cut and divided into a plurality of piezoelectric elements, and at the same time, the diaphragm is also cut to form the grooves, so that an extremely high mutual interference prevention effect can be achieved by simplifying the manufacturing process. This can be achieved without adding anything. In addition, after gluing a single flat piezoelectric element onto the diaphragm, the piezoelectric element is cut to correspond to the boundary between the pressurizing chambers, and at the same time, a cut is made to the diaphragm to form a groove. , it becomes possible to easily achieve high-density arrangement by making the width of the piezoelectric element fine. In addition, since it is possible to ensure high positional accuracy of the piezoelectric element with respect to each pressurizing chamber and with respect to each groove, there is no variation in drive between each pressurizing chamber, and the particle size of ink ejected from each nozzle can be adjusted.
This enables good inject recording with uniform speed, direction, etc., and neat fonts. Furthermore, in the present invention, by forming a groove within the thickness of the diaphragm in the diaphragm, compared to the case where a groove is formed by making a cut beyond the thickness of the diaphragm and reaching the partition wall between the pressurizing chambers. hand,
Since the thickness of the partition wall between the pressurizing chambers does not need to be greater than the width of the groove, the partition wall can be made thinner, and the flow channels can be arranged with higher density accordingly. Furthermore, the bonding strength between the diaphragm and the substrate can be ensured. Furthermore, if a groove is formed extending from the diaphragm to the partition wall between the pressurizing chambers, the partition wall will become substantially thinner and mutual interference between adjacent pressurizing chambers will increase, but in the case of the present invention, the diaphragm Since the grooves are formed within the same thickness, the thickness of the partition walls between the pressurizing chambers remains unchanged, and mutual interference does not increase.

[Brief explanation of drawings]

Fig. 1 is a multi-nozzle head that has been proposed in the past, Fig. 2 is a sectional view of the main part showing an embodiment of the present invention, and Fig. 3 is a sectional view of the main part showing an embodiment different from the embodiment shown in Fig. 2. It is. 12, 22...Diaphragm, 13,23...Slot, 1
4, 24...Piezoelectric element.

Claims (1)

[Claims] 1. An ink flow path having a plurality of nozzles and pressurized chambers communicating with each nozzle is formed by a space facing a substrate and a diaphragm, and a piezoelectric element is laminated on the diaphragm. In the method for manufacturing an inkjet head, a single flat piezoelectric element is bonded on the diaphragm, and then the piezoelectric element is cut into a plurality of piezoelectric elements corresponding to the boundary between the pressurizing chambers. At the same time, a cut is made up to the diaphragm to form a groove within the thickness of the diaphragm in the diaphragm.