JP3173189B2 - 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 an ink jet head for performing recording on a recording medium by flying ink droplets.

[0002]

2. Description of the Related Art In an on-demand type ink jet head using a conventional piezoelectric actuator, Japanese Patent Publication No.
As described in JP-A-73348, a drive unit in which a laminated piezoelectric vibrator is processed into a slit shape is joined to a flow path forming unit,
Some have achieved higher density and improved assemblability.

Here, the structure of the conventional example will be described with reference to FIG. The flow path 21 is formed by the flow path wall 26 of the elastic body, the base substrate 52, and the bonding layer 42 (flow path forming portion). A large-sized laminated piezoelectric vibrator is bonded to the substrate 32 and then slit to form a plurality of piezoelectric vibrators 30 (drive unit). The drive unit and the flow path forming section are
Each piezoelectric vibrator 30 (the width of the piezoelectric vibrator 30 is larger than the width of the flow path 21) is joined to each flow path 21 so as to face each other. Then, the nozzle plate 10 forming the nozzle 11
However, as shown in the figure, the nozzle 11 and the flow path 21 are joined to the end surface of the joined body of the drive unit and the flow path forming portion so as to be aligned. In this configuration, when the flow path 21 is filled with ink and the piezoelectric vibrator 30 is driven, a volume change occurs in the flow path 21, and the ink is ejected from the nozzle 11.

FIG. 17 shows a conventional example in which the flow paths 21 are formed on both surfaces of a base substrate 52 to increase the number of nozzles and increase the density and speed. Here, 90 is a drive IC body.

[0005]

However, in the structure of the conventional example, when the piezoelectric vibrator 30 is driven in a state where the ink is filled in the flow path 21, each component (the piezoelectric vibrator 30,
The flow path wall 26 and the base substrate 52) are actually deformed as shown by a dotted line in FIG. As can be seen from the figure, the deformation of the piezoelectric vibrator 30 not only causes a volume change in the flow path 21 but also propagates along the flow path wall 26 and the D
Causes an amount of variation. The fluctuation amount D1 increases as the number of the driven piezoelectric vibrators 30 increases. Further, since the base substrate 52 and the substrate 32 are joined only by the nozzle plate 10, the further away from the nozzle plate 10, the greater the amount of variation D 1. Naturally, said fluctuations result in a very large loss of drive energy.

A phenomenon caused by a very large pressure generated in the flow path 21 will be described with reference to FIG. (For the sake of illustration, a structure in which the width of the piezoelectric vibrator 30 is smaller than the width of the flow path 21 is applied.) The solid line in FIG. 19 indicates a state in which the piezoelectric vibrator 30 has already been deformed due to ink ejection. ing. In this state, a very large pressure is generated in the flow path, and this pressure is applied to the flow path 21 via the ink.
(The flow path wall 26, the base substrate 52,
It is instantaneously propagated to the bonding layer 42) and deforms and fluctuates in a direction to expand the volume in the flow path 21. Due to this pressure, each constituent member of the flow path 21 is deformed as shown by a dotted line in the figure, and as a result, the amount of D2 changes in the base substrate 52. (Here, for the sake of explanation, the piezoelectric vibrator 30 and the substrate 32
Was immovable. That is, the pressure generated in the flow path 21 is not effectively used only for ink discharge, but is lost as a fluctuation of the base substrate 52.

As described above, in the structure of the prior art, the loss caused by mechanically fluctuating the base substrate 52 via the flow path wall 26 and the pressure generated in the flow path by the base substrate 5.
2 together with the loss that causes the drive energy to fluctuate, an enormous loss of drive energy results. Therefore, the ink ejection efficiency is extremely poor. In addition, the fluctuation of the base substrate 52 of the above two mechanisms (mechanical one through the flow path wall 26 and one due to the pressure in the flow path 21) is modeled by the magnitude of the width of the piezoelectric vibrator 30 with respect to the width of the flow path 21. Although described in a different manner, the mechanism is not limited by the model, and although the magnitude of influence is large, the two mechanisms are combined and the base substrate 52 fluctuates.

Further, the fluctuation of the base substrate 52 (the base substrate 52 oscillates with a damping vibration of the maximum amplitude D1 or D2).
As a result, the ink flow in the flow path 21 is disturbed (the ink meniscus formed at the tip of the nozzle 11 becomes unstable), and the ink ejection is very unstable.

In addition, when flow paths are formed on both sides of the base substrate 52 as shown in FIG. 17, fluctuations of the base substrate 52 due to driving on each surface interfere with each other in a complicated manner, and the driving state between the surfaces (see FIG. 17). For example, inter-plane crosstalk, in which the ejection characteristics fluctuate due to the difference in the number of driving lines, appears.

Accordingly, the present invention is to solve such a problem, and an object of the present invention is to suppress fluctuation of a flow path substrate (having the same function as the base substrate), to achieve high efficiency and stable ink ejection. An object of the present invention is to provide an inkjet head having high performance.

In addition, the present invention is also applied to a head compatible with a double-sided flow path, and provides a high-quality ink jet head having high density, high efficiency, high ink ejection stability, and no inter-surface crosstalk by increasing the number of nozzles. It is also an object of the present invention.

[0012]

In order to solve the above-mentioned problems, an ink jet head according to the present invention is provided in which a plurality of ink flow grooves are formed on a surface of a flow path substrate. Alternate multiple piezoelectric and conductive layers at corresponding locations
In the ink jet head having a drive unit in which the stacked vibrators stacked on each other are arranged, the drive unit further includes a piezoelectric vibrator portion that does not face the ink flow path, and the flow path substrate and the drive unit The piezoelectric vibrator is sandwiched between the first fixed plate on the flow path substrate side and the second fixed plate on the drive unit side, and the piezoelectric vibrator vibrates in the holding direction.
Then, a diaphragm facing the ink flow path is pressed . More preferably, the length of the piezoelectric vibrator portion not facing the ink flow path in the holding direction is longer than the length of the piezoelectric vibrator portion facing the ink flow path. More preferably, the second fixing plate is a member that holds the piezoelectric vibrator of the drive unit. Further, the flow path substrates are joined to both sides of the first fixed plate, and the drive unit is sandwiched between the second fixed plates from both sides.

[0013]

[0014]

According to the above construction, the first and second rigid fixing plates join the flow path substrate and the drive unit via the piezoelectric vibrator portion (dummy piezoelectric vibrator) which does not face the ink flow path. Since the body is sandwiched, the joint between the flow path substrate and the drive unit is not initially deformed. And since it is pinched by the rigid body, the said joined body does not fluctuate in the pinching direction when the piezoelectric vibrator is driven when the drive unit is driven.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIGS. 1, 2 and 3 are structural views for explaining a first embodiment of the present invention. FIG. 1 is a sectional view perpendicular to the ink discharging direction, and FIG. FIG. 3 is a perspective view having a partial cross section.

A plurality of grooves for forming the flow path 21 are formed on the surface of the flow path substrate 20 made of a polymer resin, ceramic, glass, metal, or the like by molding, etching, machining, or the like. Then, an elastic film 40 (resin film, metal thin film, or the like) is bonded on the surface thereof, and the flow path 21 is closed, forming a flow path forming part as a whole.

After bonding the large-sized laminated piezoelectric vibrator to the substrate 32, a plurality of piezoelectric vibrators 30 and the piezoelectric vibrator 30
Slitting is performed so as to divide the dummy piezoelectric vibrators 31 at both ends of the group to form a drive unit as a whole.
Naturally, the driving piezoelectric vibrator 30 is divided at the same pitch as the arrangement pitch of the flow paths 21. The stacked state of the piezoelectric vibrator 30 is set such that the common electrodes of each layer are arranged at both ends in the longitudinal direction of the flow path 21. (See Fig. 2)
Here, the driving piezoelectric vibrator 30 and the dummy piezoelectric vibrator 3
Since 1 is formed from a single laminated vibrator, the height in the laminating direction (vertical direction in the drawing) is uniform. But,
When the height variation is assumed due to the thickness accuracy or the adhesion accuracy of the laminated vibrator before the slit processing, after the large-sized laminated vibrator is bonded to the substrate 32, lapping and polishing are performed, and then the slit processing is performed. It is desired to do. still,
The slit processing is performed by machining such as dicing or cutting with a wire saw, various kinds of etching, laser processing, electric discharge machining, ultrasonic processing, etc., alone or in combination.

Further, as other parts of the drive unit,
An electric signal line 80 (FFC, FPC, etc.) for transmitting a signal to each piezoelectric vibrator 30 is required, and a substrate 32
It is electrically connected to the electrode pattern formed thereon by bonding, soldering, wire bonding, mechanical pressing, or the like.

The piezoelectric vibrator 30 and the elastic film 40 oppose the flow path forming portion and the drive unit, and the driving piezoelectric vibrators 30 and the flow paths 21 are joined so as to correspond in position. . In this state, the dummy piezoelectric vibrator 31 does not correspond to the flow channel 21 and is joined to the rigid portion of the flow channel substrate 20 via the elastic film 40.

Then, as shown in the figure, the first fixed plate 50 on the side of the flow path forming section and the second fixed plate 60 on the side of the driving unit are used to screw the joined body between the flow path forming section and the driving unit to a screw 70. It is pinched by using. Here, the first fixed plate 50 and the second
The fixing plate 60 needs to be rigid so as not to be deformed by tightening with the screw 70. Therefore, as the material, a material having a high elastic modulus such as metal, ceramic, and glass is preferable. In addition, if the material has a low elastic modulus, it is desired to increase the thickness. The first fixing plate 5 is shown in the drawing.
0 is formed with a female thread and corresponds to the screw 70, but a simple hole is formed in the first fixing plate 50, and a nut is formed from the back surface (the lower side in the figure) of the first fixing plate 50. It does not matter.
Further, the clamping method is not limited to the screw fixing, but may be fixed by a spring, the first and second fixing plates 50 and 6 may be used.
The shape of 0 may be devised to cope with the adhesion between the two.

Then, the nozzle plate 10 forming the plurality of nozzles 11 is joined to the end surface of the joined body of the drive unit and the flow passage forming portion by aligning the positions of the nozzles 11 and the flow passages 21 as shown in FIG. Have been. Here, the joint area between the nozzle plate 10 and the joined body extends to the first fixed plate 50 and the second fixed plate 60. However, the substrate 32, the flow path, The region up to the substrate 20 may be used. In the above configuration, since the height dimension between the substrate 32 and the elastic film 40 is mechanically regulated by the dummy piezoelectric vibrator 31, the flow path is formed by the first and second fixing plates 50 and 60 which are rigid bodies. Even if the joined body of the unit and the drive unit is pressed and sandwiched, the elastic film 40 on the flow path 21 is initially deformed,
It does not give an initial stress (maintained in a stressed state). Accordingly, the volume change efficiency in the flow path 21 with respect to the input energy of the piezoelectric vibrator 30 is extremely high, and highly efficient ink flight is achieved.

Since the height of each piezoelectric vibrator 30 is uniform, the bonding state of the piezoelectric vibrators 30 in each flow path 21 is also uniform. Accordingly, ink flight without variation in characteristics over the plurality of nozzles 11 is achieved.

The first and second fixing plates 5 which are rigid bodies
The joint body (the flow path substrate 20) is sandwiched between 0 and 60 and held rigidly when the drive unit is driven.
However, it does not fluctuate in the holding direction when the piezoelectric vibrator 30 is driven. Accordingly, there is no input energy loss due to the fluctuation of the flow path substrate 20 and no disturbance of the ink flow in the flow path 21 (unstable meniscus), and high-efficiency and stable ink ejection is achieved.

Next, the details of the joint between the piezoelectric vibrator 30 and the elastic film 40 will be described with reference to the drawings.

FIG. 4 shows an arrangement in which island portions 41 (projections having a shape corresponding to the shape of the flow path 21) are arranged at positions corresponding to the flow paths 21 and the piezoelectric vibrators 30 of the elastic film 40. This island part 4
1 can be formed on the elastic film 40 by pattern etching or the like, and the position accuracy of the island portion 41 can be formed with very high accuracy. Further, there is no problem even if the material is changed only in the portion of the island portion 41 due to the etching performance and the factors of the island portion forming means. However, the height of the island portion 41 (the vertical direction in the figure) needs to be the same as the joint surface between the dummy piezoelectric vibrator 31 and the elastic film 40.

In this configuration, even if the position of the piezoelectric vibrator 30 is shifted with respect to the island portion 41, the island portion 41 and the flow path 21
Is normal, the deformed state and the internal stress state of the elastic film 40 are uniform without change. Therefore, even if a displacement occurs when the drive unit and the flow path forming portion are joined, there is no problem with respect to the ink ejection characteristics.

Regarding the joint between the piezoelectric vibrator 30 and the elastic film 40, the structure shown in FIGS. 18 and 19 (combination of the width of the flow path 21 with respect to the width of the piezoelectric vibrator 30), The configuration shown in FIG. 5 (the flow channel 21 is closed with a filler 42 that is an elastic body without the elastic film 40) and the like also belong to the applicable range of the present invention.

In the first embodiment, an example has been shown in which the nozzle plate 10 is joined and the flow path 21 and the nozzle 11 are connected. However, in addition to the above-described configuration, the nozzle 12 may be formed on the flow path substrate 20 from the beginning as shown in FIG. 6, or the nozzle 13 may be formed on the flow path substrate 20 by laser processing or the like as shown in FIG. Such a configuration also falls within the scope of the present invention.

Next, a second embodiment of the present invention will be described with reference to FIG.

The difference from the first embodiment is that the drive unit is composed of only the second fixed plate 60 and the laminated piezoelectric vibrators (the driving piezoelectric vibrator 30 and the dummy piezoelectric vibrator 31). 32. This configuration corresponds to substrate 3
The purpose of the invention is to reduce the number of parts by eliminating 2, and to reduce costs by simplifying the process.

As described above, in the first and second embodiments, the flow path substrate 20 and the first fixing plate 50 have been described as being separate bodies. However, the flow path substrate 20 is formed by resin molding, Fixing plate 5
If insert molding of 0 is performed (integral molding), the number of parts in the process is substantially reduced, and the cost is reduced by reducing the number of processes. The first fixing plate 50 may be made of a different material such as metal, ceramic, glass and the like.

Also, by this insert molding, the initial positioning of the flow path substrate 20 and the first fixing plate 50 becomes very easy, and the positional relationship can be maintained for a long time. This leads to an improvement in the initial and long-term printing position accuracy on the medium.

In addition, the flow path substrate 20 and the first fixing plate 50
Are joined without any load (the positional relationship is ensured), so that it is not necessary to press the drive unit more than necessary. Therefore, the residual stress due to the pressure is very small inside the flow path substrate 20, and the reliability of the flow path substrate 20 including the ink resistance is greatly improved, and the durability and the durability as a complete ink jet head are improved. , Leading to improved reliability.

Hereinafter, the flow path substrate 20 and the first fixing plate 50
Will be described with reference to the drawings.

FIG. 9 shows an embodiment in which the nozzle-side end surfaces of the flow path substrate 20 and the first fixing plate 50 are aligned. It is desirable that the uniform end face between the different members be formed at the time of insert molding, but after insert molding, post-processing (dicing,
It may be formed by mechanical processing such as lapping or laser processing. Here, reference numeral 22 denotes a common ink chamber for supplying ink to each flow path 21, reference numeral 23 denotes an ink supply hole having the same function as the common ink chamber, and reference numeral 51 denotes a screw portion formed on the first fixing plate. In addition, the flow path substrate 20 in the insert molding is used.
In order to improve the joining force between the first fixing plate 50 and
It is desired that the surface of the fixing plate 50 is subjected to a plurality of fine groove processing, fine dimple processing, and the like to make the surface rough. Also, a great effect can be expected by forming a plurality of holes.

FIG. 10 shows an embodiment in which the end face on the nozzle side is formed by the front end portion 24 of the flow path substrate 20. In this configuration, since the first fixing plate 50 does not intervene on the nozzle tip surface, a uniform and very clean surface can be formed. In addition, since the joint surface between the flow path substrate 20 and the first fixing plate 50 is not exposed to the nozzle-side end surface, the processing reliability of the surface in a later step is improved.

FIGS. 11, 12 and 13 show the first fixing plate 5.
This is an embodiment in which a member 25 (the material is the same as that of the flow path substrate 20) having the same thickness as the flow path side is formed at the same time as the insert molding on the side opposite to the flow path formation side of No. 0. The embodiment of FIG. 9 and the embodiment of FIG. 11 have the same idea regarding the formation of the nozzle-side end surface, and the embodiment of FIG. 10 and the embodiment of FIG. 12 have the same idea. FIG. 13 is a cross-sectional view perpendicular to the ink ejection direction of both the embodiments of FIGS. In this configuration, since the first fixing plate 50 is insert-molded on both surfaces, the joining force is dramatically improved with a large expansion of the joining area. In addition, at a high temperature applied during insert molding, warpage of the flow path substrate 20 caused by a difference in the coefficient of thermal expansion between the flow path substrate 20 and the first fixing plate 50 (occurs when the temperature returns to normal temperature after molding) This can be prevented by introducing the member 25. This is because the stress applied to the first fixed plate 50 due to the contraction of the molded meat on the flow path side and the opposite flow path side is equal,
The channels cancel each other, and as a result, a flow path surface having a high flatness without warpage can be formed. Therefore, in the ink jet head using the insert molded body, the elastic film 40 and the piezoelectric vibrator 30 joined to the channel surface having high flatness are provided.
Is in a uniform state over all the flow paths 21, and a more uniform ink discharge without variation can be achieved.

Next, a description will be given of a third embodiment in which the first and second embodiments are applied to a double-sided flow path compatible head for the purpose of increasing the number of nozzles, with reference to FIG.

The structure of one side (upper or lower in the figure) is basically the same as that of either of the first and second embodiments. 20
Are arranged, and the drive unit is sandwiched by the second fixing plate 60 from both sides. According to this configuration, the first and second
In addition to the effect similar to that of the embodiment, the variation of the flow path substrate 20 in the holding direction (vertical direction in the drawing) is completely suppressed on each surface, so that cross-talk between the surfaces can be prevented. Absent.

In FIG. 14, the flow paths on both sides are arranged at the same pitch without any deviation between the surfaces. However, the amount of this deviation may be selected depending on the purpose such as high-speed operation and high-density operation.

FIG. 15 shows an embodiment in which the flow path substrates 20 on both sides and the first fixing plate 50 are insert-molded.
1, the same effect as that of the embodiment shown in FIG. 12 can be obtained, and the double-sided flow path can be formed simultaneously.

[0043]

As described above, the present invention can provide an ink jet head which suppresses fluctuation of the flow path substrate, is highly efficient, and has high ink ejection stability.

In addition, the present invention is also applied to a double-sided flow path compatible head, and provides a high-quality ink jet head having high density, high efficiency, high ink ejection stability and no inter-surface crosstalk by increasing the number of nozzles. can do.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view perpendicular to the ink ejection direction of a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the first embodiment of the present invention, taken along an ink ejection direction.

FIG. 3 is a perspective view with a partial cross section of the first embodiment of the present invention.

FIG. 4 is a detailed view of a joint portion of the piezoelectric vibrator according to the present invention.

FIG. 5 is a detailed view of a joined portion of the piezoelectric vibrator according to the present invention.

FIG. 6 is a detailed perspective view of a nozzle-side tip portion of a flow path substrate according to the present invention.

FIG. 7 is a detailed perspective view of a nozzle-side tip portion of a flow path substrate according to the present invention.

FIG. 8 is a sectional view perpendicular to the ink ejection direction of a second embodiment of the present invention.

FIG. 9 is a perspective view of an insert molded body of the flow path substrate and the first fixing plate according to the present invention.

FIG. 10 is a perspective view of an insert molded body of the flow path substrate and the first fixing plate according to the present invention.

FIG. 11 is a perspective view of an insert molded body of the flow path substrate and the first fixing plate according to the present invention.

FIG. 12 is a perspective view of an insert molded body of the flow path substrate and the first fixing plate according to the present invention.

FIG. 13 is a cross-sectional view of an insert molded body of the flow path substrate and the first fixing plate according to the present invention.

FIG. 14 is a vertical sectional view with respect to an ink ejection direction according to a third embodiment of the present invention.

FIG. 15 is a cross-sectional view of an insert molded body of the flow path substrate and the first fixing plate according to the present invention.

FIG. 16 is a perspective view of the vicinity of a conventional nozzle.

FIG. 17 is a main schematic sectional view of a conventional example.

FIG. 18 is a detailed sectional view of a conventional example.

FIG. 19 is a detailed view of a main section of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Nozzle plate 11, 12, 13 Nozzle 20 Flow path board 21 Flow path 22 Common ink chamber 23 Ink supply hole 24 Flow path board tip part 25 Flow path board same thickness member 26 Flow path wall 30 Piezoelectric vibrator 31 Dummy piezoelectric vibrator Reference Signs List 32 substrate 40 elastic film 41 elastic film island portion 42 bonding layer 50 first fixing plate 51 first fixing plate screw portion 52 base substrate 60 second fixing plate 70 screw 80 electric signal line 90 drive IC body D1 fluctuation Quantity D2 Fluctuation

Continuation of front page (56) References JP-A-3-2042 (JP, A) JP-A-4-247944 (JP, A) JP-A-55-42862 (JP, A) JP-A-1-186330 (JP) JP-A-62-10052 (JP, A) JP-A-61-144360 (JP, A) JP-A-3-221457 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) B41J 2/045 B41J 2/055

Claims (4)

(57) [Claims] 1. A laminated vibration in which a plurality of piezoelectric layers and conductive layers are alternately laminated at positions corresponding to the plurality of ink flow paths on a flow path substrate having a plurality of ink flow path grooves formed on a surface thereof. In the ink jet head having a drive unit in which the elements are arranged, the drive unit further has a piezoelectric vibrator portion that does not face the ink flow path, and the flow path substrate and the drive unit, The piezoelectric vibrator is sandwiched between the first fixed plate on the flow path substrate side and the second fixed plate on the drive unit side, and the piezoelectric vibrator vibrates in the holding direction to be in the ink flow path.
An ink jet head characterized by pressing an opposing diaphragm . 2. The piezoelectric vibrator portion not facing the ink flow path, the length in the holding direction of the piezoelectric vibrator portion being longer than the length of the piezoelectric vibrator portion facing the ink flow path. Inkjet head. 3. The ink jet head according to claim 1, wherein the second fixing plate is a member that holds the piezoelectric vibrator of the drive unit. 4. The apparatus according to claim 1, wherein the flow path substrates are joined to both sides of the first fixed plate, and the drive unit is sandwiched between the second fixed plates from both sides. An inkjet head according to any one of the preceding claims.