JPH0929963A - Ink jet type print head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet type print head, in which no fear of crosstalk and poor discharge is present and which has high printing quality even in multiple pin simultaneous printing. SOLUTION: Since a cavity plate 34 is so constituted that its ink chambers bend in the neighborhood of a manifold and some parts of side walls separating the ink chambers 32 adjacent to each other from each other locate beneath an actuator, the cavity plate 34 and the actuator can be joined together not only at the bonding parts 51 and 53 at the outer edge parts of the cavity plate but also at the bends 52 between the ink chambers 32 and the manifold 90, resulting in improving the stiffness of the cavity plate 34. As a result, the cavity plate 34 is restricted from being deformed and warped, resulting in obtaining high printing quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a cavity provided in an ink jet type print head for ejecting ink droplets to form dots or characters on a print medium.

[0002]

2. Description of the Related Art In recent years, among the non-impact type recording apparatuses, which have replaced the existing impact type recording apparatuses and are greatly expanding the market, the principle is the simplest, and multi-gradation and colorization are realized. As easy as
An inkjet type recording apparatus can be used. Inkjet printers are attracting attention because they have advantages such as high-speed printing, low noise, high printing quality, and a relatively simple structure and low manufacturing cost.

A plurality of methods have been proposed for an ink jet type print head used in an ink jet printer. Among them, a drop-on-demand type which ejects only ink droplets used for recording has good ejection efficiency and running cost. It is rapidly spreading due to its low price.

In an ink jet type print head using a piezoelectric element, which is an example thereof, a part of the wall surface of the ink flow path is deformed by the displacement of the piezoelectric element to which a voltage is applied, and pressure is applied to the ink in the ink flow path. By doing so, ink droplets are ejected from the nozzle.

The ink jet type print head is shown in FIG.
As shown in FIG. 10, the tip portion is divided into a plurality of pieces, each of which has a columnar piezoelectric ceramic 81 that is selectively displaced in the vertical direction, and is elastic so as to follow the deformation of the tip portion of the piezoelectric ceramic 81. The thin plate 82, a resin-made cavity plate 84 in which an ink chamber 83 communicating with the nozzle and a manifold are formed, and a reinforcing plate 85 for restricting the deformation direction of the piezoelectric ceramics 81 are bonded together. The tip portions of the piezoelectric ceramics 81 are arranged so as to be located above the ink flow paths 83, and support the cavity plate 84 at the outer edge portion thereof.

Electric wiring of a driver is connected to each tip of the piezoelectric ceramics 81 by wire bonding or the like, and a driving voltage is supplied through the electric wiring. The tip of the piezoelectric ceramics 81 is displaced by the application of the drive voltage, and the thin plate 82 is deformed to apply pressure to the ink in the ink flow path 83, thereby ejecting ink droplets from the nozzles for printing. .

[0007]

However, in the above-mentioned ink jet type print head, the cavity plate 8 is used.
Since a large number of grooves and recesses for the ink chambers 83 and the manifolds arranged in a high density are formed in 4, the rigidity of the cavity plate 83 is likely to be insufficient. Further, the tip end portions of the columnar piezoelectric ceramics 81 are separated from each other, and as shown in FIG. 9, the cavity plate 84 is supported only by both longitudinal edge portions thereof. The interval L is long.

Therefore, in the conventional ink jet type print head, the bonding strength between the piezoelectric ceramics 81 and the cavity plate 84 is small, and the cavity plate 84 is easily deformed by an external force. Therefore, when the piezoelectric ceramic 81 is driven, the displacement of the piezoelectric ceramic 81 is not limited to the corresponding ink chamber 83,
It easily spreads over the entire cavity plate 84. That is, the displacement of the piezoelectric ceramic 81 not only causes the volume change of the ink chamber 83 itself, but also acts to bend the entire cavity plate 84 outward or deform it in the twisting direction.

If the cavity plate 84 is curved so as to escape outward, the desired volume change of the ink chamber 83 is hindered, and it becomes difficult to apply pressure to the ink efficiently. On the contrary, if the cavity plate 84 is deformed in the twisting direction, it causes unnecessary pressure fluctuations in the adjacent ink chambers 83 and the like.

This phenomenon occurs particularly remarkably when a plurality of ink chambers 83 are simultaneously ejected, that is, when a large displacement is applied to the cavity plate 84 at one time. In some cases, defective ejection of ink or crosstalk frequently occurs, so that there is a problem that the ink jet print head does not have sufficient characteristics.

In order to eliminate the above ejection failure, it is possible to increase the driving voltage to increase the pressure applied to the ink chamber 83. However, even if the driving voltage is increased, the curvature of the cavity plate 84, which is the root of the problem, and the like. The distortion such as the twist has not been resolved. Therefore, there still remain problems such as crosstalk and variations in the diameter and speed of ink droplets ejected depending on the number of piezoelectric ceramics 81 that are simultaneously driven.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide an inexpensive ink jet print head having high print quality by suppressing escape and distortion during printing of a cavity member. To aim.

[0013]

In order to achieve this object, an ink jet print head of the present invention is provided with a plurality of ink chambers communicating with ink ejection nozzles and a manifold for supplying ink to each ink chamber. The cavity member and the ink chamber are respectively disposed so as to face each other,
And a plurality of actuator means for ejecting small ink droplets by applying mechanical vibration to the ink in the corresponding ink chamber, and a part of the side wall separating adjacent ink chambers near the manifold is bent, Means are configured to support the cavity member by the bent portion of the side wall and the outer edge portion of the cavity member where the ink chamber is not formed.

The actuator means has three outer edges of the cavity member, one edge portion and the other edge portion located in the longitudinal direction of the ink chamber, and the bent portion of the side wall. The member may be supported.

It should be noted that the actuator means may be displaced only at a portion facing a region sandwiched between the ink discharge nozzle and the bent portion of the ink chamber.

The actuator means may be a laminated piezoelectric element in which piezoelectric layers made of a piezoelectric material and electrode layers are alternately laminated.

The ink is solid at normal temperature,
It may be a heat-meltable ink that is melted by heating during printing.

[0018]

In the ink jet type print head according to the first aspect of the present invention having the above structure, the side wall of the cavity member forming the ink chamber is bent near the manifold side, and even at the bent part of the side wall. It is configured to be supported by the actuator means. Therefore, the actuator means and the intermediate portion from the ink discharge nozzle to the manifold can be joined, and the rigidity of the cavity member can be improved. As a result, discharge pressure loss and crosstalk due to distortion such as bending and twisting of the cavity member due to the generated pressure in the ink chamber, which is a problem at the time of simultaneous ejection, are suppressed, and high print quality is obtained.

In the ink jet print head according to a second aspect of the present invention, the actuator means is an outer edge portion of the cavity member, one edge portion and the other edge portion located in the longitudinal direction of the ink chamber, and the bent portion of the side wall. The cavity member is supported at three points. Therefore, the bonding between the actuator member and the cavity member becomes reliable,
Furthermore, since the rigidity of the cavity member can be improved, high quality printing quality can be obtained.

In the ink jet print head according to a third aspect of the present invention, the actuator means is displaced only at a portion facing a region sandwiched between the ink discharge nozzle and the bent portion of the ink chamber, and is joined to the cavity member. It does not displace at the part or the part facing the manifold. Therefore, the displacement of the actuator means can be efficiently added to the ink in the ink chamber as mechanical vibration.

In the ink jet type print head according to the fourth aspect, since the actuator means is composed of a so-called laminated piezoelectric element, it is possible to perform efficient driving in which a large displacement can be obtained even at a low voltage.

In the ink jet type print head according to the fifth aspect, since the heat-meltable ink having a relatively high viscosity is used, the ink jet print head is not affected by the change in the fluid resistance of the ink chamber due to the formation of the bent portion, and the Ink is reliably supplied.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying the present invention will be described in detail with reference to FIGS.

FIG. 7 shows a main part of an ink jet printer equipped with an ink jet type print head according to an embodiment of the present invention. A platen 10 in the drawing is rotatably attached to a frame 13 by a shaft 12 and driven by a motor 14. Paper 11 on the platen 10
Is set, and an ink jet type print head 15 is provided so as to face the platen 10. The inkjet print head 15 is mounted on the carriage 18 together with the ink supply device 16. The carriage 18 is slidably supported by two guide rods 20 arranged parallel to the axis of the platen 10, and the pair of pulleys 2
The timing belt 24 wound around 2 is coupled. Then, one pulley 22 is rotated by the motor 23, and the timing belt 24 is sent, whereby the carriage 18 is moved along the platen 10.

1 to 3 show the structure and cross section of the array 30 used in the ink jet print head 15. As shown in FIG. The array 30 includes a cavity plate 34 in which a plurality of ink chambers 32a, 32b, 32c extending in a direction perpendicular to the plane of the drawing and a manifold 90 are formed, and a thin film vibration plate 35 on the cavity plate 34. An orifice plate 3 having a fixed laminated piezoelectric element 38 and an orifice 37 fixed to the cavity plate 34 on the side opposite to the laminated piezoelectric element 38.
6 and the ink chambers 32a of the laminated piezoelectric element 38.
32c and a base plate 33 made of a metal or ceramic having a high elastic modulus fixed to the opposite side.

The ink chambers 32a to 32c are filled with ink, and the ink is appropriately supplied from the ink supply device via the manifold 90. The ink of this embodiment is a so-called hot melt ink which is solid at room temperature and melts by heating. Although not shown, the ink jet printer of this embodiment is provided with a heater or the like in the ink flow path for using the hot melt ink in a molten state.

Ink jet type print head 1 of this embodiment
The laminated piezoelectric element 38 in No. 5 has a piezoelectric ceramic layer 40 having a piezoelectric / electrostrictive effect, an internal negative electrode layer 42,
A plurality of internal positive electrode layers 44 are laminated. As shown in FIGS. 3 and 4, the laminated piezoelectric element 38 is slit by a dicer or the like at a pitch such that one end surface thereof corresponds to the ink chambers 32a to 32c on a one-to-one basis. And has a comb-like structure including the actuator 39 divided into a plurality of parts. The width of the actuator 39 is smaller than the width of the ink chamber 32, and the free end of the actuator 39 is located in each ink chamber 3.
It is arranged so as to correspond to 2.

In each actuator 39, as shown in FIGS. 2 and 4, an internal negative electrode layer 42 and an internal positive electrode layer 44 are provided at a substantially central portion in the longitudinal direction of the actuator 39 via a piezoelectric ceramic layer 40. Only stacked to intersect. The area where the two electrode layers 42 and 44 intersect is the piezoelectric active portion 46, and the other area is the piezoelectric inactive portion 4.
Make up eight. The piezoelectric active portion 46 of each actuator 39 is formed at a portion facing a region sandwiched between the orifice 37 of the ink chamber 32 and a bent portion 52 described later.

The piezoelectric ceramic layer 40 is made of a lead zirconate titanate (PZT) -based ceramic material having ferroelectricity, and is polarized in the stacking direction. The arrow shown in the piezoelectric ceramics layer 40 of FIG. 2 has shown the polarization direction. In addition, each electrode layer 42, 4
Reference numeral 4 denotes an internal negative electrode layer 4 made of an Ag-Pd-based metal material.
Part 2 of the internal positive electrode layer 44 is exposed at one end face in the longitudinal direction of the actuator 39, and part of it is exposed at the other end face in the longitudinal direction. Then, a conductive layer is formed on the exposed end faces of the electrodes 42 and 44, and an external negative electrode 55 and an external positive electrode 54 are formed. Actuator 3
When an electric field is applied between the electrode layers 42 and 44 of No. 9, the piezoelectric active portion 46 causes piezoelectric deformation in the thickness direction. However, no deformation occurs in the piezoelectric inactive portion 48 that is the other region.

On the other hand, the cavity plate 34 is molded by injection molding using a resin material, and as shown in FIG. 5, a plurality of ink chambers 32 arranged in parallel and a manifold 90 communicating with them are formed. There is. In the ink chambers 32a to 32c corresponding to the above-mentioned comb-shaped actuator 39, the portion of the side wall separating the adjacent ink chambers 32 located near the manifold 90 is located below the actuator 39. It has a bent structure. As a result, the bent portion 52 is
It is joined to the actuator 39 by sandwiching it.

The cavity plate 34 is shown in FIGS.
As shown in FIG.
2 and the outer edge portion of the manifold 90 where the concave portion is not formed and the bent portion 52. Also, in terms of the ink chamber 32, the first adhesive portion 51 and the second adhesive portion 53, which are the outer edge portion of the cavity plate and are one edge portion located in the longitudinal direction of the ink chamber 32. The actuator 39 is supported at three points with the bent portion 52 of the side wall.

The bent portion 5 is formed so that the fluid resistance of the ink chamber 32 is not increased by forming the bent portion 52 and the ink replenishment from the manifold 90 is not hindered.
The bending angle of 2 is preferably small. In this embodiment, since hot melt ink having a high viscosity is generally used, the ink can be reliably supplied from the manifold 90 regardless of the change in the fluid resistance of the ink chamber 32.

Further, each of the arrays 30 shown in FIG.
The electrical circuit shown in FIG. In this electric circuit, the negative electrode side of the driving power source 60 and the laminated piezoelectric element 3
8 is grounded to the external negative electrode 55, and the positive electrode side of the drive power source 60 is connected to the external positive electrodes 54a to 54 of the laminated piezoelectric element 38 via the open / close switches 62a, 62b, and 62c.
4c. These switches 62a to 62c
Is closed by a controller (not shown), so that the drive power source 60 drives the predetermined actuators 39a to 39a.
A drive voltage is applied between the internal negative electrode layer 42 and the internal positive electrode layer 44 located at 9c.

The operation of the ink jet type print head 15 constructed as above will be described. Although the number of channels is three for convenience of explanation, the present invention is not limited to this embodiment.

When the controller closes the switch 62a, for example, according to predetermined print data, a voltage is applied between the internal negative electrode layer 42 and the internal positive electrode layer 44a of the actuator 39a, and the piezoelectric ceramics located between them. A bias electric field is applied to the layer 40, and the piezoelectric active portion 46 of the actuator 39a expands in the vertical direction in the drawing according to the dimensional strain of the piezoelectric / electrostrictive longitudinal effect, and the ink chamber 32
Reduce the volume of a. Then, the ink in the ink chamber 32a is ejected as droplets from the orifice 37a.
When the switch 62a is opened and the voltage application is cut off and the piezoelectric active portion 46 of the actuator 39a is returned to its original position, the ink supply is performed via another valve (not shown) as the volume of the ink chamber 32a increases at that time. Ink is replenished from the device 16. Note that, for example, when the other switch 62b is closed, the piezoelectric active portion of the actuator 39b is displaced and ink is ejected from the ink chamber 32b.

That is, the array 30 of the present embodiment includes the three ejecting devices 70a, 7a of the ink jet type print head 15.
0b and 70c, and one laminated piezoelectric element 38 functions as a piezoelectric actuator provided across the three ejection devices 70a to 70c.

Here, a state of deformation in the array direction 31 when a voltage is applied to the laminated piezoelectric element 38 is shown. When a voltage of 25 V is applied to the actuator 39, the portion of the piezoelectric active portion 46 where the internal negative electrode layer 42 and the internal positive electrode layer 44 intersect with each other undergoes a large displacement of 200 nm or more, and the portion deviated from the piezoelectric active portion 46. (Piezoelectric inactive section 4
In 8), there is almost no displacement. However, at the end of the piezoelectric active portion 46, the piezoelectric active portion 46 is displaced by the displacement of the piezoelectric active portion 46. From this result, in order to efficiently deform the laminated piezoelectric element 38 into the ink chamber 32, the length of the piezoelectric active portion 46 in the longitudinal direction is smaller than the length of the ink chamber 32 in the longitudinal direction. I find it necessary. In the present embodiment, the length of the piezoelectric active portion 46 of the actuator 39 in the longitudinal direction is set smaller than the length of the ink chamber 32, so that a low driving voltage of only 30 V is sufficient for ejecting the droplet 39. Good injection can be performed.

The problem here is that when the ink chamber 32 is lengthened, the rigidity of the portion where the ink chamber 32 is formed is reduced,
This is that the cavity plate 34 is easily distorted by the pressure generated by the laminated piezoelectric element 38 during printing. Therefore, the generated pressure escapes or spreads to other ink chambers 32,
Ink ejection performance is likely to be adversely affected (for example, non-uniformity or non-ejection suitable for ink liquid, crosstalk, etc.). However, in the ink jet type print head 15 of the present embodiment, the vicinity of the manifold 90 of the ink chamber 32 is bent to form the bent portion 52, and the cavity plate 34 can be bonded and fixed also at the bent portion 52. The rigidity of the ink chamber 32 is remarkably increased, and the distortion of the cavity plate is prevented. As a result, it is possible to provide an inkjet printer with high print quality even when simultaneous ejection is performed, because the loss of generated pressure and crosstalk are suppressed.

Further, in the piezoelectric ink jet printer 15 of this embodiment, since one laminated piezoelectric element 38 functions as a piezoelectric actuator of the plurality of ejecting devices 70a to 70c, the array 30, and moreover, the array 30 thereof, are arranged in a large number. By assembling, the structure of the ink jet type print head 15 is simplified, the number of manufacturing steps is reduced, and the manufacturing cost is reduced. In addition to the piezoelectric actuator being the laminated piezoelectric element 38, the length of the ink chamber 32 in the extension direction is set to the actuator portion 4.
Since it is larger than 6, the efficient deformation can be obtained, and thus the driving voltage can be significantly reduced.

The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the invention.

[0041]

As is apparent from the above description, in the ink jet type print head of the present invention, the ink chamber formed in the cavity member is bent near the manifold so that the side wall forming the ink chamber is bent. A part is configured to overlap the actuator means. Therefore, the cavity member and the actuator means can be joined not only to the outer edge portion but also to the ink chamber and the manifold, and the rigidity of the cavity member is improved. As a result, escape and distortion of the cavity member, which is a problem at the time of simultaneous ejection from a plurality of ink chambers, are suppressed, and high print quality without ejection failure or crosstalk can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of an array forming an ink jet print head according to an embodiment of the present invention.

FIG. 2 is a side sectional view of an array of this embodiment.

FIG. 3 is a partially cutaway cross-sectional view of the array of this embodiment.

FIG. 4 is a perspective view of a laminated piezoelectric element used in the ink jet print head of this embodiment.

FIG. 5 is a plan view of a cavity used in the ink jet print head of this embodiment.

FIG. 6 is an explanatory diagram showing a state in which an electric circuit is provided in the array of this embodiment.

FIG. 7 is a perspective view showing a main part of an inkjet printer equipped with the inkjet print head of the present embodiment.

FIG. 8 is a perspective view showing a configuration of a conventional ink jet print head.

FIG. 9 is a side sectional view of a conventional ink jet print head.

FIG. 10 is a cross-sectional view of a conventional inkjet printhead.

[Explanation of symbols]

 32 Ink Chamber 34 Cavity Plate 38 Laminated Piezoelectric Element 39 Actuator 46 Piezoelectric Active Part 48 Piezoelectric Inactive Part 51 First Adhesive Part 52 Bent Part 53 Second Adhesive Part 90 Manifold

Claims (5)

[Claims] 1. A cavity member having a plurality of ink chambers communicating with the ink ejection nozzles and a manifold for supplying ink to the respective ink chambers, and a cavity member arranged to face the ink chambers. A plurality of actuator means for ejecting small ink droplets by applying mechanical vibration to the ink in the ink chamber, a part of the side wall separating adjacent ink chambers near the manifold is bent, and the actuator means is An ink jet print head configured to support the cavity member by a bent portion of the side wall and an outer edge portion of the cavity member where the ink chamber is not formed. 2. The cavity is provided at three points of an outer edge portion of the cavity member, one edge portion and another edge portion located in a longitudinal direction of the ink chamber, and a bent portion of the side wall. The ink jet print head according to claim 1, which supports a member. 3. The actuator means is displaced only at a portion facing a region sandwiched between the ink discharge nozzle and the bent portion of the ink chamber.
Or the ink jet type print head according to item 2. 4. The ink jet printing according to claim 1, wherein the actuator means comprises a laminated piezoelectric element in which piezoelectric layers made of a piezoelectric material and electrode layers are alternately laminated. head. 5. The ink jet print head according to claim 1, wherein the ink is a solid ink at room temperature and a heat-meltable ink that is melted by heating during printing.