JP3669010B2 - Inkjet print head - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an ink jet print head that forms ink characters or figures on a print medium by flying ink droplets.
[0002]
[Prior art]
In recent years, it has replaced the conventional impact-type recording devices, and the principle is the simplest among the non-impact-type recording devices that are greatly expanding the market, and the multi-gradation and colorization are easy. As an example, an ink jet recording apparatus may be used. Inkjet printers are attracting attention because they have advantages such as high-speed printing, low noise, high printing quality, and low manufacturing costs with a relatively simple configuration.
[0003]
Several types of inkjet print heads used in inkjet printers have been proposed. Among them, the drop-on-demand type, which ejects only ink droplets used for recording, has good ejection efficiency and low running costs. It is rapidly spreading.
[0004]
An example of such an ink jet print head using a piezoelectric element is to deform a part of the wall surface of an ink flow path by displacement of a piezoelectric element to which voltage is applied, and apply pressure to the ink in the ink flow path. Ink droplets are ejected from the nozzles.
[0005]
As shown in FIGS. 8 to 10, the ink jet print head includes a columnar piezoelectric ceramic 81 having a tip portion divided into a plurality of portions, each of which is selectively displaced in the vertical direction, and a tip portion of the piezoelectric ceramic 81. An elastic thin plate 82 that follows the deformation of the ink, an ink chamber 83 communicating with the nozzle, a resin cavity plate 84 formed with a manifold, and a reinforcing plate 85 that regulates the deformation direction of the piezoelectric ceramic 81 are bonded. It has a configuration. The tip portions of the piezoelectric ceramics 81 are disposed so as to be located above the ink flow paths 83, and support the cavity plate 84 at the outer edge thereof.
[0006]
Electric wiring of a driver is connected to each tip portion of the piezoelectric ceramic 81 by wire bonding or the like, and a driving voltage is supplied through the electric wiring. The tip of the piezoelectric ceramic 81 is displaced by the application of the driving 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]
[Problems to be solved by the invention]
However, in the ink jet print head, the cavity plate 84 is formed with a large number of grooves and recesses for the ink chamber 83 and the manifold arranged at high density, and the rigidity of the cavity plate 83 tends to be insufficient. Further, the tip 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 edges in the longitudinal direction. The interval L is longer.
[0008]
Therefore, in the conventional ink jet 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 easily spread not only to the corresponding ink chamber 83 but also to the entire cavity plate 84. That is, the displacement of the piezoelectric ceramic 81 not only causes a change in the volume of the ink chamber 83 alone, but also acts to bend the entire cavity plate 84 outward or deform it in the twisting direction.
[0009]
If the cavity plate 84 is curved so as to escape outward, the desired volume change of the ink chamber 83 is hindered, making it difficult to efficiently apply pressure to the ink. Conversely, if the cavity plate 84 is deformed in the twisting direction, unnecessary pressure fluctuations are caused in the adjacent ink chamber 83 and the like.
[0010]
This phenomenon occurs particularly noticeably when a plurality of ink chambers 83 are simultaneously ejected, that is, when a large displacement is given to the cavity plate 84 at a time. In some cases, defective ink discharge and crosstalk frequently occur, and there is a problem that the ink jet print head does not have sufficient characteristics.
[0011]
In order to eliminate the ejection failure, a method of increasing the driving voltage to increase the pressure applied to the ink chamber 83 can be considered. However, even if the driving voltage is increased, the cavity plate 84, which is the root of the problem, may be bent or twisted. Distortion has not been eliminated. 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 driven simultaneously.
[0012]
The present invention has been made to solve the above-described problems, and an object thereof is to provide an inexpensive ink jet print head having high print quality by suppressing escape and distortion during printing of a cavity member. .
[0013]
[Means for Solving the Problems]
In order to achieve this object, an ink jet print head according to the present invention includes a cavity member formed with a plurality of ink chambers communicating with ink discharge nozzles and a manifold for supplying ink to each ink chamber, and opposed to the ink chamber. Actuator means having a plurality of active portions that are each arranged to cause the ink in the corresponding ink chamber to mechanically vibrate and eject ink droplets, and connect the ink chamber and the manifold. a portion, bent laterally with respect to the extending direction of the line connecting both ends of the ink chamber, said manifold near the side walls separating the ink chambers adjacent along it in line some bending to the extension direction located in the lower portion of said actuator means, said actuator means comprises a bent portion of the side wall, the cavity portion It is fixed to the cavity member across the outer edge portion to which the ink chamber opposite to the bent portion is not formed in the.
[0014]
The actuator means is an outer edge portion of the cavity member, and the cavity means at three points, one edge portion and another edge portion located at both ends in the longitudinal direction of the ink chamber, and a bent portion of the side wall. It may be fixed to the member.
[0015]
The actuator means may be such that the active portion displaced with respect to the ink chamber is shorter than the length between both ends of the ink chamber .
[0016]
The actuator means may be composed of a laminated piezoelectric element in which piezoelectric layers and electrode layers made of a piezoelectric material are alternately laminated.
[0017]
[0018]
[Action]
In the ink jet type print head according to the first aspect of the present invention having the above-described configuration, a portion connecting the ink chamber and the manifold is set laterally with respect to an extending direction of a line connecting both ends of the ink chamber. bent, located in the lower portion of said actuator means in line in the extension direction the manifold near the side walls separating the ink chambers adjacent Correspondingly bent part, a bent portion of the side wall, the cavity member Actuator means is fixed across the bent portion and the outer edge portion where the opposite ink chamber is not formed. Therefore, the rigidity of the cavity member can be improved. As a result, discharge pressure drop and crosstalk caused by distortion such as bending and twisting of the cavity member due to pressure generated in the ink chamber, which becomes a problem during simultaneous ejection, are suppressed, and high print quality can be obtained.
[0019]
In the ink jet type print head according to claim 2, the actuator means is an outer edge portion of the cavity member, one edge portion and the other edge portion located at both ends in the longitudinal direction of the ink chamber, and a bent portion of the side wall. The cavity member is supported at three points. Therefore, the actuator member and the cavity member are reliably joined, and the rigidity of the cavity member can be further improved, so that high-quality print quality can be obtained.
[0020]
In the ink jet print head according to the third aspect, the actuator means is displaced only between both ends of the ink chamber , and is not displaced at the joint portion with the cavity member or the manifold facing portion. Therefore, the displacement of the actuator means, efficient ink chamber of the ink to the machine械的it can be added as a vibration.
[0021]
In the ink jet print head according to the fourth aspect, since the actuator means is formed of a so-called laminated piezoelectric element, it is possible to perform efficient driving that can obtain a large displacement even at a low voltage.
[0022]
[0023]
【Example】
An embodiment embodying the present invention will be described in detail with reference to FIGS.
[0024]
FIG. 7 shows a main part of an ink jet printer equipped with an ink jet 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 is driven by a motor 14. A paper 11 is set on the platen 10, and an ink jet print head 15 is provided so as to face the platen 10. The ink jet print head 15 is placed on a carriage 18 together with an ink supply device 16. The carriage 18 is slidably supported by two guide rods 20 disposed parallel to the axis of the platen 10, and a timing belt 24 wound around a pair of pulleys 22 is coupled thereto. One pulley 22 is rotated by a motor 23, and the timing belt 24 is sent to move the carriage 18 along the platen 10.
[0025]
1 to 3 show a configuration and a cross section of an array 30 used in the ink jet print head 15. The array 30 includes a cavity plate 34 formed with a plurality of ink chambers 32a, 32b, 32c and a manifold 90 extending in a direction perpendicular to the paper surface in the figure, and a thin film-like vibrating plate 35 on the cavity plate 34. The laminated piezoelectric element 38 fixed, the orifice plate 36 having the orifice 37 fixed to the cavity plate 34 on the opposite side of the laminated piezoelectric element 38, and the ink chambers 32a to 32a of the laminated piezoelectric element 38. A base plate 33 made of a metal or ceramic having a high elastic modulus, which is fixed to the side facing 32c, is provided.
[0026]
The ink chambers 32 a to 32 c are filled with ink, and 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 that is solid at room temperature and is melted by heating. Although not shown, the ink jet printer of the present embodiment is provided with a heater or the like in the ink flow path in order to use hot melt ink in a molten state.
[0027]
The multilayer piezoelectric element 38 in the ink jet print head 15 of this embodiment is formed by laminating a plurality of piezoelectric ceramic layers 40 having a piezoelectric / electrostrictive effect, an internal negative electrode layer 42, and an internal positive electrode layer 44. . As shown in FIGS. 3 and 4, the laminated piezoelectric element 38 is slitted 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. It has a comb-like structure including an 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 actuator 39 is arranged so that the free end thereof corresponds to each ink chamber 32.
[0028]
In each actuator 39, as shown in FIGS. 2 and 4, the internal negative electrode layer 42 and the internal positive electrode layer 44 intersect only at the substantially central portion in the longitudinal direction of the actuator 39 via the piezoelectric ceramic layer 40. Are stacked. A region where the electrode layers 42 and 44 intersect constitutes the piezoelectric active portion 46, and the other region constitutes the piezoelectric inactive portion 48. 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.
[0029]
The piezoelectric ceramic layer 40 is composed of a lead zirconate titanate (PZT) ceramic material having ferroelectricity and is polarized in the stacking direction. The arrows shown in the piezoelectric ceramic layer 40 in FIG. 2 indicate the polarization direction. Each of the electrode layers 42 and 44 is made of an Ag—Pd-based metal material, and a part of the internal negative electrode layer 42 is exposed at one end face in the longitudinal direction of the actuator 39, and the internal positive electrode layer 44 is a part of it. Is exposed at the other end surface in the longitudinal direction. A conductive layer is formed on the end face where each of the electrodes 42 and 44 is exposed, and an external negative electrode 55 and an external positive electrode 54 are formed. When an electric field is applied between the electrode layers 42 and 44 of the actuator 39, the piezoelectric active part 46 causes piezoelectric deformation in the thickness direction. However, no deformation occurs in the piezoelectric inactive portion 48 which is another region.
[0030]
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 therewith are formed. In the ink chambers 32 a to 32 c corresponding to the above-described comb-shaped actuator 39, a portion located in the vicinity of the manifold 90 on the side wall that separates the adjacent ink chambers 32 is positioned below the actuator 39. It has a bent structure. As a result, the bent portion 52 is joined to the actuator 39 with the diaphragm 35 interposed therebetween.
[0031]
As shown in FIGS. 2 and 5, the cavity plate 34 is supported by the laminated piezoelectric element 38 at the outer edge portion where the concave portions of the ink chamber 32 and the manifold 90 are not formed and the bent portion 52. Further, when viewed in units of the ink chamber 32, the outer edge portion of the cavity plate and the first adhesive portion 51, which is one edge portion located in the longitudinal direction of the ink chamber 32, and the second adhesive portion 53 of the other edge portion, The actuator 39 is supported at three points with the bent portion 52 of the side wall.
[0032]
It is preferable that the bending angle of the bending portion 52 is made small so that the fluid resistance of the ink chamber 32 is not increased by forming the bending portion 52 and the ink replenishment from the manifold 90 is not hindered. In this embodiment, since hot melt ink having a high viscosity is generally used, the ink is reliably supplied from the manifold 90 regardless of the change in the fluid resistance of the ink chamber 32.
[0033]
Each array 30 is provided with an electric circuit shown in FIG. In this electric circuit, the negative side of the driving power source 60 and the external negative electrode 55 of the laminated piezoelectric element 38 are grounded, and the positive side of the driving power source 60 is connected to the laminated type via open / close switches 62a, 62b, 62c. The external positive electrodes 54a to 54c of the piezoelectric element 38 are connected. When each of the switches 62a to 62c is closed by a controller (not shown), a drive voltage is applied between the internal negative electrode layer 42 and the internal positive electrode layer 44 located at predetermined actuators 39a to 39c from the drive power supply 60.
[0034]
The operation of the ink jet print head 15 configured as described above will be described. For convenience of explanation, the number of channels is three, but the present invention is not limited to this embodiment.
[0035]
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 ceramic layer 40 positioned between them is applied. A bias electric field is applied, and the piezoelectric active portion 46 of the actuator 39a expands in the vertical direction in the drawing in accordance with the dimensional distortion of the piezoelectric / electrostrictive longitudinal effect, thereby reducing the volume of the ink chamber 32a. The ink in the ink chamber 32a is ejected as droplets from the orifice 37a. Further, when the switch 62a is opened and voltage application is cut off and the piezoelectric active portion 46 of the actuator 39a is returned to the original position, the ink supply is made through another valve (not shown) along with the increase in the volume of the ink chamber 32a at that time. Ink is replenished from the device 16. 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.
[0036]
That is, the array 30 of this embodiment constitutes the three ejection devices 70a, 70b, 70c of the ink jet print head 15, and one laminated piezoelectric element 38 straddles the three ejection devices 70a-70c. It functions as a piezoelectric actuator provided.
[0037]
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 each other is greatly displaced by 200 nm or more, and is a portion separated from the piezoelectric active portion 46 The (piezoelectric inactive portion 48) hardly displaces. However, the end of the piezoelectric active portion 46 is somewhat displaced by being dragged by the displacement of the piezoelectric active portion 46. From this result, in order to efficiently deform the stacked piezoelectric element 38 into the ink chamber 32, the length in the longitudinal direction of the piezoelectric active portion 46 is smaller than the length in the longitudinal direction of the ink chamber 32. It turns out that it is necessary. In the present embodiment, the length of the piezoelectric active portion 46 of the actuator 39 in the longitudinal direction is made smaller than the length of the ink chamber 32. Good injection can be performed.
[0038]
The problem here is that the longer the ink chamber 32, the lower the rigidity of the portion where the ink chamber 32 is formed, and the cavity plate 34 is easily distorted by the pressure generated by the laminated piezoelectric element 38 during printing. For this reason, the generated pressure escapes or spreads to the other ink chambers 32, and the ink ejection performance is easily adversely affected (for example, unevenness of ink liquid, non-ejection, crosstalk, etc.). However, in the ink jet 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 to the bent portion 52 as well. The rigidity of the ink chamber 32 is remarkably increased, and the cavity plate is prevented from being distorted. As a result, it is possible to provide an ink jet printer having high print quality even during simultaneous injection, with the occurrence of generated pressure and crosstalk being suppressed.
[0039]
Further, in the piezoelectric ink jet printer 15 of the present embodiment, since one laminated piezoelectric element 38 functions as a piezoelectric actuator of a plurality of ejection devices 70a to 70c, the array 30 and further a large number of the arrays 30 are assembled. The structure of the ink jet 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 multilayer piezoelectric element 38, the length of the ink chamber 32 is made larger than the actuator portion 46 in the extending direction, so that efficient deformation can be obtained, so that the driving voltage is greatly reduced. did it.
[0040]
In addition, this invention is not limited to the said Example, Many modifications can also be added in the range which does not deviate from the meaning.
[0041]
【The invention's effect】
As is apparent from the above description, in the ink jet print head of the present invention, the portion connecting the ink chamber and the manifold is set laterally with respect to the extending direction of the line connecting both ends of the ink chamber. bent, located in the lower portion of said actuator means in line in the extension direction the manifold near the side walls separating the ink chambers adjacent Correspondingly bent part, a bent portion of the side wall, the cavity member Actuator means is fixed across the outer edge where the ink chamber on the opposite side is not formed. Therefore, the rigidity of the cavity member can be improved, the escape and distortion of the cavity member, which is a problem when simultaneously ejecting from a plurality of ink chambers, is suppressed, and high print quality without defective ejection and crosstalk can be obtained.
[Brief description of the drawings]
FIG. 1 is a perspective view showing the configuration of an array constituting an ink jet print head according to an embodiment of the present invention.
FIG. 2 is a side sectional view of the array of this example.
FIG. 3 is a partially cutaway cross-sectional view of the array of this example.
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 the present 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 ink jet printer equipped with the ink jet 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 ink jet print head.
[Explanation of symbols]
32 Ink chamber 34 Cavity plate 38 Multilayer piezoelectric element 39 Actuator 46 Piezoelectric active part 48 Piezoelectric inactive part 51 First adhesive part 52 Bending part 53 Second adhesive part 90 Manifold

Claims (4)

A cavity member formed with a plurality of ink chambers communicating with the ink discharge nozzles and a manifold for supplying ink to each ink chamber;
Actuator means each having a plurality of active portions that are respectively disposed so as to face the ink chambers and cause mechanical vibrations to be applied to the ink in the corresponding ink chambers to eject ink droplets;
Wherein the portion for connecting the ink chamber and the manifold, bent laterally with respect to the extending direction of the line connecting both ends of the ink chamber, the manifold near the side walls separating the ink chambers adjacent part Correspondingly bent to the line of the extending direction is located in the lower portion of said actuator means, said actuator means comprises a bent portion of the side wall, are formed said ink chamber opposite to the bent portion in the cavity member An ink jet print head, wherein the ink jet print head is fixed to the cavity member across an outer edge portion.   The actuator means is an outer edge portion of the cavity member, and is provided on the cavity member at three points: one edge portion and another edge portion located at both ends in the longitudinal direction of the ink chamber, and a bent portion of the side wall. The ink jet print head according to claim 1, wherein the ink jet print head is fixed. 3. The ink jet print head according to claim 1, wherein the actuator unit is configured such that the active portion displaced with respect to the ink chamber is shorter than a length between both ends of the ink chamber .   4. The ink jet print head according to claim 1, wherein the actuator means comprises a laminated piezoelectric element in which piezoelectric layers and electrode layers made of a piezoelectric material are alternately laminated.

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