JP2002347244A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink jet head for use in a recorder forming an ink image on a recording medium b flying ink drops in which accuracy of bonding position between channel forming members can be ensured easily and variation is suppressed in the ink ejection characteristics. SOLUTION: Reference hole of a channel forming member has protrusions at three or more positions toward the center and has an axis symmetric shape where the diameter of inscribed circle at the protrusion is smaller than the outside diameter of a reference pin. Engaging position of the reference pin is different between overlapping channel forming parts. Furthermore, total engaging length is set shorter than one half of the outer circumferential length of the reference pin.

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 used in a recording apparatus for forming an ink image on a recording medium by causing ink droplets to fly by pressure generated by pressure generating means. More specifically, the present invention relates to a structure for positioning the head components with each other.

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-demand type ink jet head using pressure generating means, and more particularly to a multi-nozzle ink jet head having a large number of nozzles integrated at a high density. The on-demand type inkjet head ejects ink by a thermal method in which bubbles are generated in the ink by an electric heater to eject the ink, and an ink in which a part of the wall of the pressure chamber is deformed by using a piezoelectric element. And a piezoelectric element method for injecting. The thermal method has the advantage that fine processing can be performed by lithography technology and the nozzle pitch can be reduced to 100 μm or less, but the boiling point of the liquid to be jetted is limited to about 100 ° C., and the driving frequency during continuous jetting is low. There is a disadvantage that it is limited to about 10 kHz. Since the restriction of the boiling point restricts the type of ink, it may hinder industrial applications. On the other hand, in the piezoelectric element method, the amount of displacement of the piezoelectric element is small, and it is necessary to increase the surface area of the diaphragm of the pressure chamber for ink ejection. Therefore, the nozzle pitch can be reduced only to about 100 μm. However, since the drive frequency depends on the shape of the piezoelectric element, if the dimensions of the piezoelectric element are appropriately selected, the frequency can be increased to 20 kHz or more, which can be said to be a method suitable for increasing the printing speed. Further, unlike the thermal method, there is an advantage that the type of ink is not selected, and it is possible to eject high-viscosity ink found in industrial use. Accordingly, it is expected that the need for the piezoelectric element type ink jet will increase in the future. The present invention relates to a piezoelectric element system.

As a conventional example of a method for manufacturing an ink jet head, in Japanese Patent Application Laid-Open No. 11-58749, a flow path forming member from an orifice plate to a support plate and a common ink supply path is formed by passing a reference pin through a reference hole provided in each plate. , Alignment at the time of bonding was performed. In order to perform alignment with high precision, it is necessary to precisely manufacture the dimensions of the reference pin and the reference hole to the same size. However, the dimensions of the reference pin and the reference hole cannot be completely matched in manufacturing. From the viewpoint of component processing, in the case of a general metal or resin material used in the manufacture of an inkjet head, the processing dimensional accuracy of the reference hole and the reference pin is ± 10 μm in practical use.

When assembling using a reference pin,
If the reference hole is smaller than the reference pin, a large resistance is involved in the process of inserting the reference pin into the reference hole of each plate constituting the flow path forming member. Therefore, as shown in FIG. Such deformation causes a positional shift between the plates constituting the flow path forming member, and a gap t occurs between the plates. As a result, defects such as poor adhesion between the plates occur. In addition, it causes the reference pin 21 to bend or be damaged, which is a factor of causing an assembly failure.

[0005] Therefore, in assembling, it is necessary to make the reference hole larger by several μm than the reference pin, and a gap x as shown in FIG. 4 is inevitably generated. Further, as shown in FIG.
Taking into account the manufacturing accuracy of parts ± 10 μm to the gap x, the position error y between the flow path forming members after assembly is about 50 μm at the maximum.

In order to obtain higher precision, a reference hole diameter of each plate is measured in advance, a plate having a close measured value is selected, and a reference pin having a diameter suitable for the selected plate is used. This is possible by performing an assembly operation. However, the above-mentioned method results in a very low yield and high cost manufacturing method.

FIG. 6 is a partial cross-sectional view of an ideal ink jet head when the flow path forming member is assembled with little displacement. However, in actual assembling, due to the dimensional difference between the reference hole and the reference pin, the respective plates constituting the flow path forming member are displaced as shown in the cross-sectional view of the ink jet head shown in FIG. . In the example of FIG. 6, the thin portion of the diaphragm is uniformly displaced with the deformation of the piezoelectric element, so that the change in the volume of the liquid chamber is stable, and the nozzle position is also coincident with the center of the diaphragm. Is highly efficient, and characteristics such as a discharge speed and a discharge volume are stabilized. Further, since the thin portion of the vibration plate is located evenly in the direction of expansion and contraction of the piezoelectric element, lateral stress is not generated in the piezoelectric element, and characteristics such as life are improved.

On the other hand, in the example shown in FIG. 7, the thin portion of the vibration plate is displaced unevenly, and in the worst case, the piezoelectric element pushes the non-deformed flow path forming member. And the characteristics such as the discharge speed and the discharge volume become unstable. In addition, the ink jet head may not discharge at all, which significantly lowers print quality. In addition, since the thin portion of the diaphragm is unequally positioned with respect to the expansion and contraction direction of the piezoelectric element, lateral stress is generated in the piezoelectric element, and failure such as breakage of the piezoelectric element or damage of the thin portion of the diaphragm is caused. And adversely affect the life characteristics.

[0009]

When the reference hole is smaller than the reference pin, the reference hole of each plate is deformed non-uniformly, which causes a problem such as poor adhesion between the plates. Also, when the reference hole is larger than the reference pin, a positional error after assembly occurs, resulting in poor ink ejection efficiency, and unstable characteristics such as ejection speed and ejection volume.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet head which can reduce variations in ink ejection characteristics and can easily ensure the accuracy of the bonding position between the plates constituting the flow path forming member.

[0011]

According to the present invention, there is provided a pressure chamber comprising: a plurality of pressure chambers for storing ink; a pressure generating means for generating a pressure fluctuation in the pressure chamber by applying an electric signal; A diaphragm that forms at least a part of the wall surface of the and that is connected to the pressure generating means, and a restrictor serving as a flow path for supplying ink to the pressure chamber;
A common ink supply path for supplying ink to the restrictor, a nozzle serving as an ejection port for ejecting ink droplets from the pressure chamber, and a flow path forming member that forms a part of the ink flow path has a plurality of flow paths. Formed by laminating plates,
In an inkjet head that determines a bonding position by fitting two or more assembling reference holes provided in the plurality of plates with reference pins, at least one reference hole has at least three reference holes toward the center. It has a plurality of convex portions, and the diameter of the inscribed circle of the convex portions is smaller than the outer diameter of the reference pin and has an axially symmetric shape.

Further, in the present invention, the positions where the plurality of projections of the reference hole and the reference pin are engaged are different between the overlapping flow path forming portions.

Further, in the present invention, the total length of engagement of the plurality of projections of the reference hole and the reference pin is smaller than 1/2 of the outer peripheral length of the reference pin. .

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view illustrating the structure and component structure of an ink jet head according to the present invention.
FIG. 2 is a partial cross-sectional view showing an assembled state of the inkjet head according to the present invention.

Reference numeral 2 denotes an orifice plate on which a plurality of nozzles 1 are formed. The processing accuracy of the opening shape of the nozzle 1 is as follows.
This has a great effect on the ink ejection characteristics of the inkjet head. The orifice plate 2 is used to reduce the variation in nozzle accuracy among a plurality of nozzles.
The production method requires high processing accuracy. For this reason, the orifice plate 2 is formed by electroforming of nickel, precision pressing of a stainless steel plate or the like, or laser processing.

Reference numeral 4 denotes a chamber plate in which the pressure chambers 3 are formed. Reference numeral 6 connects the common ink supply path 11 and the pressure chambers 3 to form a restrictor 5 for controlling the amount of ink flowing into the pressure chambers 3. It is a restrictor plate. The chamber plate 4 and the restrictor plate 6 are made by a stainless steel etching method or a nickel material electroforming method.

Reference numeral 10 denotes a vibration plate 7 for efficiently transmitting the pressure of the laminated piezoelectric element 14 to the pressure chamber, an island-shaped rigid projection 8 not shown in FIG. And a filter portion 9 for removing dust and the like in the ink flowing into the filter plate. The diaphragm plate 10 has two layers, a diaphragm plate A101 and a diaphragm plate B102. The diaphragm plate A101 has a thickness of about 20
The filter portion 9 was made of a polymer resin film such as a polyimide resin having a thickness of μm, and the filter portion 9 was formed by laser processing with innumerable fine holes smaller than the hole diameter of the nozzle 1. Diaphragm plate B102 is made of stainless steel having a thickness of about 50 μm, and is adhered to diaphragm plate A101 by bonding.
The island-shaped rigid projections 8 were formed by the etching method.

Reference numeral 12 denotes a housing in which a common ink passage 11 is formed. The housing 12 is made of metal or resin, and is joined to an ink introduction pipe 13 for leading ink from an external ink tank to the common ink passage 11.

Next, an example of the present invention will be described in more detail.

In FIG. 1, the flow path forming member is composed of a housing 12 and each plate, wherein each plate includes an orifice plate 2, a chamber plate 4,
Restrictor plate 6 and diaphragm plate 10
And The method of assembling the flow path forming member is performed as follows.

First, two reference holes 24 of the housing 12 are provided.
Then, two reference pins 21 are press-fitted.

Next, with the two reference pins 21 being aligned, other plates coated with an appropriate amount of an adhesive such as an epoxy resin are sequentially stacked and pressed. Here, each plate has one reference hole 22 into which the reference pin 21 fits, and a long hole 23 for the rotation stop.

In this embodiment, the reference hole 22 is formed in a triangular shape as shown in FIG. 8, and the diameter φH of the inscribed circle is set to be smaller than the reference pin outer diameter φP by at least 20 μm.
By adopting such a shape, when the reference pin 21 is inserted into the reference hole 22 and the three contact portions which are substantially convex inside the reference hole 22 are slightly deformed, the reference pin 21
Means that the fitting interval can be zero. In addition, since the reference hole shape is an axially symmetric shape, the deformation caused by inserting the reference pin becomes uniform at each projection, and the center of the reference pin is
Be sure to match the center of the reference hole.

As described above, since each plate can be fitted at an interval of 0 without receiving a large resistance in the process of inserting the reference pin 21 into the reference hole 22, the deformation of each plate and the reference pin 2
1 can be prevented from being bent and damaged, and an accurate assembly state can always be achieved. The shape of the reference hole 22 may be any shape as long as there are three or more contact portions with the reference pin 21. For example, as shown in FIGS.
The same function is achieved in a shape having two convex portions.

Further, as shown in FIG. 11, as another example of the present invention, between each of the plates overlapping each other, the shape of one reference hole 22 is rotated by 180 degrees with respect to the center of the other overlapping reference hole. Shape. As in this example,
The position where the reference hole of the reference hole 22 engages with the reference pin is formed so as to be at a different position between the respective overlapping plates. Further, as shown in FIG. By making the total not more than の of the circumference of the reference pin, the deformed portions of the reference hole 22 due to the fitting of the plates do not interfere with each other as in the cross-sectional shape shown in FIG. Means that the accuracy of the assembled state is better.

Hereinafter, the assembly of the pressure generating means will be described.

The pressure generating means 18 comprising a plurality of laminated piezoelectric elements 14 and a support substrate 15 for fixing the same is positioned and joined. The order of manufacturing the pressure generating means 18 is as follows. First, a plurality of bar-shaped laminated piezoelectric elements are arranged and adhered to the support substrate 15. The support substrate 15 has high rigidity,
Alternatively, the material having a higher Young's modulus is preferably used for the laminated piezoelectric element 14.
Can be transmitted to the diaphragm 7 efficiently,
A ceramic substrate was used. Thereafter, the rod-shaped laminated piezoelectric element is divided by cutting using a dicing saw, a wire saw, or the like. At this time, each of the divided laminated piezoelectric elements 14 corresponds to one of the pressure chambers.

Further, in FIG. 2, on both surfaces of the support substrate 15, individual electrodes 16 for sending electric signals independent of an external drive circuit to the respective laminated piezoelectric elements 14 and a common electrode 17 are formed. ing. The common electrode 17 is wired to the common electrode 17 side of the support substrate 15 by a through hole, and is connected to the flexible cable 19 at a time. The terminal of the flexible cable 19 is connected to an external drive circuit.

When a selective electric signal is applied to the laminated piezoelectric element 14 from an external drive circuit, the laminated piezoelectric element 14 is distorted. Since the laminated piezoelectric element 14 is bonded on the support substrate 15 having high rigidity, the diaphragm 7 is preferentially displaced through the island-shaped rigid projections 8, and the pressure chamber 3 is displaced.
Increase pressure.

The ink jet print head described in this embodiment is used in an apparatus for forming an ink image on a recording medium by discharging ink from the nozzles 1 based on such a principle.

[0032]

As described above, according to the present invention,
Since the reference hole has a shape having a convex portion, the reference pin and the reference hole are engaged with each other. Therefore, the dimensional difference is reduced to zero, so that the positional error caused by the assembly between the flow path forming members can be always accurately determined. In addition, it is possible to provide an ink jet head capable of improving the production yield.

Further, it is possible to provide an ink jet head in which the characteristics such as the ink discharge speed and the discharge volume are stable, the life is improved, and as a result, the print quality is improved.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating the structure and component configuration of an inkjet head according to an embodiment of the present invention.

FIG. 2 is a partial sectional view showing an assembled state of an example of the present invention.

FIG. 3 is a cross-sectional view illustrating an example of a fitted state of a reference hole and a reference pin of a conventional inkjet head.

FIG. 4 is a cross-sectional view showing another example of a fitting state of a reference hole and a reference pin of a conventional inkjet head.

FIG. 5 is a plan view showing an assembly error between plates forming a flow path forming member when alignment is performed using a reference hole and a reference pin of a conventional inkjet head.

FIG. 6 is a cross-sectional view showing a state where the flow path forming member is accurately positioned and assembled.

FIG. 7 is a cross-sectional view showing a state where the flow path forming member is abnormally positioned and assembled.

FIG. 8 is a plan view showing a first example of a reference hole according to the present invention.

FIG. 9 is a plan view showing a second example of the reference hole of the present invention.

FIG. 10 is a plan view showing a third example of the reference hole of the present invention.

FIG. 11 is a partial perspective view illustrating an assembled state of an example of the present invention.

FIG. 12 is a plan view illustrating an assembled state of an example of the present invention.

FIG. 13 is a cross-sectional view showing a fitted state of a reference hole and a reference pin according to an example of the present invention.

[Explanation of symbols]

1 is a nozzle, 2 is an orifice plate, 3 is a pressure chamber, 4
Is a chamber plate, 5 is a restrictor, 6 is a restrictor plate, 7 is a vibrating plate, 8 is an island-shaped rigid projection, 9 is a filter section, 10 is a diaphragm plate, 101 is a diaphragm plate A, 102 is a diaphragm plate B, 11 Is a common ink supply path, 12 is a housing, 13
Is an ink introduction pipe, 14 is a laminated piezoelectric element, 15 is a support substrate, 16 is an individual electrode, 17 is a common electrode, 18 is a pressure generating means, 19 is a flexible cable, 20 is a conductive bonding member, 21 is a reference pin, 22 is a reference hole, 23 is a long hole, 24 is a reference hole, 30 is an adhesive, and 31 is a fixing adhesive.

Claims (3)

[Claims] A plurality of pressure chambers for storing ink; pressure generating means for generating pressure fluctuations in the pressure chambers by applying an electric signal; and pressure generating means forming at least a part of a wall surface of the pressure chambers. A connected vibration plate, a restrictor serving as a flow path for supplying ink to the pressure chamber, a common ink supply path for supplying ink to the restrictor, and ejection for ejecting ink droplets from the pressure chamber A flow path forming member, which is constituted by a nozzle serving as a mouth and forms a part of an ink flow path, is formed of a plurality of plates, and at the time of laminating the plates, at least two or more assembling references provided on the plate are provided. In an ink jet head for determining a bonding position by fitting a hole and a reference pin, at least one reference hole has at least three reference holes toward a center. An ink jet head having more than one convex portion, wherein the diameter of the inscribed circle of the convex portion is smaller than the outer diameter of the reference pin, and has an axially symmetric shape. 2. The method according to claim 1, wherein positions at which the plurality of protrusions of the reference hole and the reference pin are engaged are different between plates constituting the flow path forming member. Inkjet head. 3. The total length of engagement of the plurality of projections of the reference hole and the reference pin is １ ／ of the circumference of the reference pin.
The inkjet head according to claim 1, wherein the size of the inkjet head is smaller than that of the inkjet head.