JP2012171319A - Liquid droplet ejection head, liquid droplet ejection device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recorder that has inexpensive and simple structure, and is excellent in heat efficiency, thereby quickly converting high-viscosity ink in a liquid chamber to low-viscosity ink.SOLUTION: The liquid droplet ejection head includes: a nozzle substrate 16 provided with a nozzle 17 for ejecting a liquid droplet; a liquid chamber substrate including a liquid chamber 18 communicated with the nozzle 17 and a liquid introducing path 15 for introducing liquid to the liquid chamber 18; a diaphragm 21 constituting a part of the liquid chamber; an electromechanical transducer 19 disposed at a spot corresponding to the liquid chamber 18 on the diaphragm 21, and deformed when voltage is applied thereto from the outside, thereby deforming the diaphragm 21, so that pressure is generated in the liquid chamber 18 to eject the liquid in the liquid chamber 18 from the nozzle 17; and a common liquid chamber 13 communicating with the liquid chamber 18 through the liquid introducing path 15 and supplying the liquid to the liquid chamber 18. A planar heat generating means 12 for heating the liquid in the common liquid chamber 13 is arranged on an outer surface of at least a part of the outer wall of the common liquid chamber 13.

Description

  The present invention relates to an inkjet head that discharges highly viscous ink such as UV ink and an inkjet recording apparatus including the inkjet head.

Paper, etc., transported using a liquid ejection device including a liquid ejection head (recording head) that ejects liquid droplets of recording liquid such as ink as an image forming apparatus such as a printer, a facsimile, a copying machine, or a combination of these In some cases, an image is formed by attaching a recording liquid onto the recording medium.
In recent years, not only conventional low-viscosity inks but also high-viscosity inks such as UV inks have been used particularly in ink jet heads that eject ink.
However, since the high-viscosity ink is inferior in flying force as compared with the low-viscosity ink, in order to obtain stable ejection, it is necessary to take measures such as increasing the driving force of the piezoelectric actuator incorporated in the inkjet head.
As another method for using high-viscosity ink in an inkjet head, there is a method in which a heater is mounted on the head, the ink is heated by the heat of the heater, and the ink is discharged after having an appropriate viscosity.

For example, Patent Document 1 (Japanese Patent Laid-Open No. 2003-136756) discloses an ink jet head having a heating means for heating and reducing the viscosity of a high viscosity ink provided inside and outside an ink supply path in a recording head. Has been.
Patent Document 2 (Japanese Patent Laid-Open No. 2005-096150) discloses a configuration in which a heater for heating ink is embedded in each manifold provided on the upper and lower surfaces of an actuator constituting an ink jet head.

However, as disclosed in Patent Document 1, if a means for heating the ink in the ink supply path is provided inside the recording head, there is a problem that the structure of the head becomes complicated.
Also, as disclosed in Patent Document 2, in the method of embedding the heater inside the manifold, the heater is covered with a resin having poor thermal conductivity because it is integrally formed by injection molding. There is a possibility that the heat transfer efficiency is poor and the ink cannot be heated sufficiently.
SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an ink jet recording apparatus capable of quickly reducing the viscosity of a highly viscous ink in a liquid chamber by having an inexpensive and simple structure and good thermal efficiency. The purpose is to do.

In order to solve the above problems, the invention of claim 1 is directed to a nozzle substrate provided with a nozzle for discharging droplets, a liquid chamber communicating with the nozzle, and a liquid for introducing liquid into the liquid chamber. A liquid chamber substrate provided with an introduction path, a vibration plate constituting a part of the liquid chamber, and a portion corresponding to the liquid chamber on the vibration plate, and deformed by applying a voltage from the outside. An electromechanical transducer that deforms the diaphragm to generate pressure in the liquid chamber and discharges the liquid in the liquid chamber from the nozzle hole, and communicates with the liquid chamber via the liquid introduction path. A liquid discharge head comprising: a common liquid chamber for supplying liquid; and a sheet-like heat generating means for heating the liquid in the common liquid chamber disposed on an outer surface of at least a part of the outer wall of the common liquid chamber. Features.
According to the present invention, the heat of the heat generating means provided on the outer wall of the common liquid chamber can be transmitted to the ink in the common liquid chamber, and the viscosity of the high viscosity ink in the liquid chamber can be lowered quickly.
Further, the invention of claim 2 includes a resin frame member that covers at least a part of the outer wall surface of the outer wall on which the heat generating means is disposed and forms a part of the outer wall of the common liquid chamber, and the heat generating means. 2. The droplet discharge head according to claim 1, wherein a thickness of an outer wall of the common liquid chamber in which is disposed is equal to or less than a half of a thickness of a frame member constituting the outer wall of the common liquid chamber.
According to the present invention, it is possible to reduce the separation between the ink stored in the common liquid chamber and the heat generating means, and the heat of the heat generating means is transmitted to the ink in a short time, so that the high viscosity ink in the liquid chamber is obtained. Can be quickly reduced in viscosity.

The invention according to claim 3 is characterized in that the outer wall of the common liquid chamber in which the heat generating means is disposed is made of a metal thin plate member.
According to the present invention, the heat of the heating means can be transmitted to the ink in a shorter time by the metal thin plate having high thermal conductivity.
According to a fourth aspect of the present invention, there is provided the droplet discharge head according to any one of the first to third aspects, wherein the metal thin plate member is integrally formed with the frame member by injection molding.
According to the present invention, the rigidity of the entire frame can be increased.
The invention according to claim 5 is characterized in that the heat generating means is a film heater, and the liquid droplet ejection head according to any one of claims 1 to 4.
According to the present invention, it is possible to easily adhere to a thin metal plate member having a limited space, and there is an effect that it is not necessary to enlarge the frame itself because the heater itself is thin.

The invention of claim 6 is characterized in that the heat generating means is a droplet discharge head according to any one of claims 1 to 5, wherein the heat generating means is joined by a highly heat conductive adhesive.
It is possible to reduce the manufacturing cost without complicating the structure of the head, and it is possible to reduce heat transfer loss by using a high thermal conductive adhesive.
According to a seventh aspect of the invention, there is provided the droplet discharge head according to any one of the first to sixth aspects, and a tank that stores a liquid to be supplied to a common liquid chamber of the droplet discharge head. It features a droplet discharge device.
According to an eighth aspect of the invention, there is provided an image forming apparatus including the droplet discharge device according to the seventh aspect.

1 is a front view illustrating an example of an inkjet head applied to an inkjet recording apparatus according to the present invention. FIG. 2 is a side view of the ink jet head shown in FIG. 1. FIG. 2 is a cross-sectional view of the inkjet head shown in FIG. 1. FIG. 2 is an exploded perspective view of the inkjet head shown in FIG. 1. Sectional drawing of the inkjet head which concerns on other embodiment of this invention. FIG. 2 is a schematic perspective view showing an ink cartridge to which the head of the present invention is applied. 1 is a perspective view illustrating an ink jet recording apparatus. The side view of the mechanism part of the inkjet recording device of FIG.

Embodiments of the present invention will be described below in detail with reference to the drawings.
1 is a front view showing an example of an ink jet head applied to the ink jet recording apparatus according to the present invention, FIG. 2 is a side view of the ink jet head shown in FIG. 1, and FIG. 3 is a diagram of the ink jet head shown in FIG. FIG. 4 is an exploded perspective view of the main part of the inkjet head shown in FIG.
In the ink jet head according to the present embodiment, a plurality of liquid chambers (pressure chambers) 19 communicating with each nozzle hole 17 are provided on a nozzle substrate 16 provided with a plurality of nozzle holes 17 as shown in FIGS. A liquid chamber substrate 18 composed of a silicon substrate or the like and a diaphragm 21 constituting a part of the liquid chamber 19 are sequentially stacked, and further, a pressure is applied to the liquid chamber 19 at a position corresponding to the liquid chamber 19 in the diaphragm 21. In addition, a piezoelectric element 14 for ejecting ink from the nozzle hole 17 is integrally provided. In FIG. 3, only one piezoelectric element, liquid chamber, and nozzle hole are displayed, but actually, a plurality of piezoelectric elements, liquid chambers, and nozzle holes may be provided in the longitudinal direction of the inkjet head.
Further, a resin frame member 10 having a common liquid chamber 13 for storing ink to be supplied to the liquid chamber 19 is laminated on the vibration plate 21.
In particular, as shown in FIG. 3, the liquid chamber substrate 18 includes a communication pipe (liquid introduction path) 15 that communicates with the common liquid chamber 13 to introduce ink into the liquid chamber 19, and a fluid resistance 20. Is provided.
In such an ink jet head, a driving IC (not shown) and a piezoelectric element 14 are joined via a wiring member 30 and a voltage is applied to the piezoelectric element 14 to deform the diaphragm 21 formed integrally with the piezoelectric element 14. Pressure is generated in the liquid chamber 19.
The deformed diaphragm 21 generates pressure on the ink filled in the liquid chamber 19, ejects the ink from the nozzle holes 17, and records an image on the recording paper.

By the way, as shown in FIG. 1 thru | or 4, in the inkjet head of this invention, among the outer walls which form the common liquid chamber 13 provided in the frame member 10, for example, two surfaces (outer wall 13a, outer wall 13b) Are provided with planar heating means (planar heating elements) 12 (12a, 12b).
By this heat generating means, the liquid (ink) stored in the common liquid chamber 13 can be heated to make the high viscosity ink have an appropriate viscosity with a simple configuration.
The frame member 10 covers at least a part of the outer wall surfaces of the outer walls 13a and 13b on which the planar heating elements 12 are arranged (reference numeral 10c) and constitutes a part of the outer wall of the common liquid chamber 13 (reference numeral 10d). . The thickness of the outer walls 13a and 13b is less than or equal to ½ of the thickness of the outer walls 10c and 10d formed by the frame member 10, so that the separation of the planar heating element 12 from the common liquid chamber 13 is small. Thus, the liquid in the common liquid chamber 13 can be heated more efficiently.
Furthermore, in FIG. 3, you may form the outer walls 13a and 13b which arrange | position the planar heating element 12 with the metal thin plate member 11 with high heat conductivity, such as stainless steel (SUS). Thereby, the heat of the heat generating means 12 can be further efficiently transmitted to the ink by the metal thin plate.

In other words, it is considered that the through holes 10a and 10b are provided in the installation positions of the planar heating elements 12 (12a and 12b) in the frame member 10, and the thin metal plate member 11 (outer walls 13a and 13b) is exposed in the through holes. You can also Then, by installing the sheet heating element 12 on the metal sheet member 11 exposed at the bottom of each through hole, the heat of the sheet heating element 12 is transmitted to the ink in a short time by the metal sheet having high thermal conductivity. I can do it.
Furthermore, since the frame member 10 is formed of a resin having low thermal conductivity as described above (the metal thin plate member 11 is not exposed), heat radiation from the entire frame member 10 can be suppressed, and the common liquid chamber can be suppressed. The temperature of the ink in 13 can be made uniform.
The metal thin plate member 11 has a thickness of 0.5 mm to 0.3 mm, and is formed into an L shape by pressing. Further, the thin metal plate member 11 has a hybrid structure that is integrally formed with the resin frame member 10 by insert injection molding. This also has the effect of increasing the rigidity of the entire frame.

Further, by fixing the planar heating elements 12a and 12b to the metal thin plate member 11 (outer walls 13a and 13b) with an adhesive, the structure of the head is not complicated, and the manufacturing cost can be reduced. In addition, heat transfer loss can be further reduced by using a high thermal conductive adhesive.
In general, a frame having a common liquid chamber includes a metal integrally-processed frame, a resin-molded frame, and a laminated metal thin plate. The metal integrated processing frame can increase the heat transfer speed, but increases the processing cost. In addition, although the resin molded frame is inexpensive, the heat transfer rate is significantly worse than that of metal. Since the frame which laminated | stacked the metal thin plate uses adhesive agents, such as an epoxy resin, there exists a possibility of deteriorating heat transfer efficiency.

In the present invention, as described above, the frame member 10 is made of resin, and only the wall of the portion where the planar heating element 12 is installed among the walls forming the common liquid chamber 13 provided in the frame member 10 is replaced with another. By reducing the wall thickness of the ink to 1/2 or less than the wall thickness, the distance between the ink stored in the common liquid chamber 13 and the sheet heating element 12 is reduced, and the ink temperature in the common liquid chamber 13 is set to the optimum temperature in a short time. Thus, the viscosity of the ink can be lowered.
Further, by setting the installation location of the planar heating element 12 to the metal thin plate member 11 exposed at the bottom of the through hole provided in the frame member 10, the heat transfer speed for the ink in the common liquid chamber 13 can be further increased. It becomes possible.
Further, the wall of the installation portion of the planar heating element 12 is made of a metal thin plate member 11 and is integrally formed with the frame member 10 by injection molding, so that the wall on which the planar heating element 12 is not installed is radiated by the heat insulation property of the resin. In addition, the wall of the planar heating element 12 installation portion can be easily formed with a hybrid frame configuration that effectively uses heat conduction efficiency having metal, and the rigidity of the frame itself can be increased. Therefore, it is difficult to be affected by ink pressure fluctuation in the common liquid chamber 13.
Further, by making the sheet heating elements 12a and 12b into film heaters, the sheet heating elements 12a and 12b can be easily bonded to a thin metal plate member with limited space, and the sheet heating elements provided on the frame because the heater itself is thin. Even if it is attached to the installation section, it does not increase the width of the frame itself, and it is not necessary to increase the size of the frame itself.

FIG. 5 is a cross-sectional view of another embodiment. The same components as those in FIGS. 1 to 4 are denoted by the same reference numerals, and detailed description thereof is omitted.
FIG. 5 is an example in which the metal thin plate member 11 is formed only on the upper surface of the common liquid chamber 13, unlike FIGS. 1 to 4, and the metal thin plate member 11 and the frame member 10 are injection molded on the upper surface of the common liquid chamber 13. Are integrated.
In order to heat the ink stored in the common liquid chamber 13 to an appropriate temperature in a short time, the area of the sheet heating element is increased, the capacity of the sheet heating element is increased, or the thermal conductivity is increased. A method of reducing the thickness of the thin metal plate member 11 or using a high thin metal plate member 11 can be considered.
Of these methods, the method of increasing the area of the planar heating element is not an optimal method because the head itself becomes larger.

Also, the method of increasing the capacity of the planar heating element is not an optimal method from the viewpoint of power consumption. Furthermore, it is conceivable that the metal thin plate member is made of a material having good thermal conductivity, such as aluminum or copper, but it is not an optimum member from the viewpoint of ink resistance.
Accordingly, the present invention increases the heat transfer speed by using a thin metal plate member on the wall on which the planar heating element is installed, and the wall on which the planar heating element is not installed has a heat insulation effect by using a resin having a low heat transfer speed. I tried to raise it. This is a hybrid structure that can stabilize the temperature of the ink.

FIG. 6 is a schematic perspective view showing an ink cartridge (liquid ejecting apparatus) to which the head of the present invention is applied.
The ink cartridge will be described with reference to FIG. The ink cartridge 50 is obtained by integrating the ink jet head 61 according to any of the above-described embodiments having the nozzle holes 17 and the like, and the ink tank 62 that supplies ink to the ink jet head 61.

FIG. 7 is a perspective view showing the ink jet recording apparatus. FIG. 8 is a side view of a mechanism portion of the ink jet recording apparatus of FIG.
An example of an ink jet recording apparatus (image forming apparatus) equipped with an ink jet head will be described with reference to FIGS.
The ink jet recording apparatus includes a carriage 93 that is movable in the main scanning direction inside the recording apparatus main body 81, a recording head that is mounted on the carriage 93 and includes an ink jet head that embodies the present invention, and an ink cartridge that supplies ink to the recording head. The printing mechanism part 82 etc. comprised by these are accommodated.
A paper feed cassette (or a paper feed tray) 84 on which a large number of sheets 83 can be stacked from the front side can be detachably attached to the lower part of the apparatus main body 81. Further, the manual feed tray 85 for manually feeding the paper 83 can be opened, the paper 83 fed from the paper feed cassette 84 or the manual feed tray 85 is taken in, and a required image is displayed by the printing mechanism unit 82. After recording, the paper is discharged to a paper discharge tray 86 mounted on the rear side.

The printing mechanism 82 holds a carriage 93 slidably in the main scanning direction by a main guide rod 91 and a sub guide rod 92 which are guide members horizontally mounted on left and right side plates (not shown).
The carriage 93 has a plurality of ink ejection openings (nozzles) of a head 94 comprising an inkjet head according to the present invention that ejects ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk). ) Are arranged in a direction crossing the main scanning direction, and the ink droplet ejection direction is directed downward. In addition, each ink cartridge 95 for supplying ink of each color to the head 94 is replaceably mounted on the carriage 93.
The ink cartridge 95 has an air port that communicates with the atmosphere upward, a supply port that supplies ink to the inkjet head below, and a porous body filled with ink inside. The ink supplied to the inkjet head is maintained at a slight negative pressure by the capillary force of the porous body. Further, although the heads 94 of the respective colors are used here as the recording heads, a single head having nozzles that eject ink droplets of the respective colors may be used.

Here, the carriage 93 is slidably fitted to the main guide rod 91 on the rear side (downstream side in the paper conveyance direction), and is slidably mounted on the sub guide rod 92 on the front side (upstream side in the paper conveyance direction). is doing.
In order to move and scan the carriage 93 in the main scanning direction, a timing belt 100 is stretched between a driving pulley 98 and a driven pulley 99 that are rotationally driven by a main scanning motor 97, and the timing belt 100 is moved to the carriage 93. The carriage 93 is driven to reciprocate by forward and reverse rotation of the main scanning motor 97.

  On the other hand, in order to convey the paper 83 set in the paper feed cassette 84 to the lower side of the recording head 94, the paper feed roller 101 and the friction pad 102 for separating and feeding the paper 83 from the paper feed cassette 84 and the paper 83 are guided. The guide member 103 to be transported, the transport roller 104 that reverses and transports the fed paper 83, the transport roller 105 that is pressed against the peripheral surface of the transport roller 104, and the feed angle of the paper 83 from the transport roller 104 are defined. A tip roller 106 is provided. The transport roller 104 is rotationally driven by a sub-scanning motor 107 through a gear train.

Corresponding to the range of movement of the carriage 93 in the main scanning direction, there is provided a printing receiving member 109 which is a sheet guide member for guiding the sheet 83 fed from the conveying roller 104 below the recording head 94.
A conveyance roller 111 and a spur 112 that are rotationally driven to send the paper 83 in the paper discharge direction are provided on the downstream side of the printing receiving member 109 in the paper conveyance direction, and the paper 83 is further delivered to the paper discharge tray 86. A roller 113 and a spur 114, and guide members 115 and 116 that form a paper discharge path are disposed.
At the time of recording, the recording head 94 is driven according to the image signal while moving the carriage 93, thereby ejecting ink onto the stopped sheet 83 to record one line. Record the line. Upon receiving a recording end signal or a signal that the trailing edge of the paper 83 has reached the recording area, the recording operation is terminated and the paper 83 is discharged.

Further, a recovery device 117 for recovering the ejection failure of the recording head 94 is disposed at a position outside the recording area on the right end side in the movement direction of the carriage 93. The recovery device 117 includes a cap unit, a suction unit, and a cleaning unit (not shown).
The carriage 93 is moved to the recovery device 117 side during printing standby, and the recording head 94 is capped by the capping unit, and the ejection port portion is kept in a wet state to prevent ejection failure due to ink drying. Further, by ejecting ink that is not related to recording during recording or the like, the ink viscosity of all the ejection ports is made constant and stable ejection performance is maintained.
When a discharge failure occurs, the discharge port (nozzle) of the recording head 94 is sealed with a capping unit, and bubbles and the like are sucked out from the discharge port with a suction unit through a tube.
Ink, dust, etc. adhering to the discharge port surface are removed by the cleaning means, and the discharge failure is recovered. The sucked ink is discharged to a waste ink reservoir (not shown) installed at the lower part of the main body and absorbed and held by an ink absorber inside the waste ink reservoir.

As described above, since the inkjet head embodying the present invention is mounted in this inkjet recording apparatus, even when a highly viscous ink such as UV ink is used, stable ink flying can be obtained, and a high quality image can be obtained. Can be obtained. Further, the configuration of the ink jet head to be used is simple and low cost.
In the above-described embodiment, the example in which the inkjet head is applied as a droplet ejection head has been described. However, as a droplet ejection head other than the inkjet head, for example, a droplet ejection head that ejects a liquid resist as droplets, The present invention can also be applied to other droplet discharge heads such as a droplet discharge head (spotter) that discharges DNA samples as droplets.

DESCRIPTION OF SYMBOLS 10 Frame member, 10a Recessed part, 10a Through hole, 10c Outer wall, 10d Outer wall, 11 Thin metal plate member, 12 Planar heating element, 13 Common liquid chamber, 13a Outer wall, 13b Outer wall, 14 Piezoelectric element, 15 Communication pipe, 16 Nozzle Substrate, 17 Nozzle hole, 18 Liquid chamber substrate, 19 Liquid chamber, 20 Fluid resistance, 21 Vibration plate, 30 Wiring member, 50 Ink cartridge, 61 Inkjet head, 62 Ink tank, 81 Recording device main body, 82 Printing mechanism section, 83 Paper, 84 Paper feed cassette, 85 tray, 86 Paper discharge tray, 91 Main guide rod, 92 Sub guide rod, 93 Carriage, 94 Recording head, 95 Ink cartridge, 97 Main scan motor, 98 Drive pulley, 99 Drive pulley, 100 Timing belt 101 Feed roller 102 Li transfection pad 103 guide member 104 conveying rollers 105 transport roller, 106 tip roller, 107 sub-scanning motor, 109 members, 111 transport roller, 112 spur, 113 discharge roller, 114 spur, 115 guide member 117 recovery device

JP 2003-136756 A JP 2005-096150 A

Claims (8)

A nozzle substrate provided with nozzles for discharging droplets;
A liquid chamber substrate including a liquid chamber communicating with the nozzle and a liquid introduction path for introducing a liquid into the liquid chamber;
A diaphragm constituting a part of the liquid chamber;
The vibration plate is provided at a position corresponding to the liquid chamber, and is deformed by applying a voltage from the outside to deform the vibration plate to generate pressure in the liquid chamber. An electromechanical transducer to be ejected from the nozzle hole;
A common liquid chamber that communicates with the liquid chamber via the liquid introduction path and supplies liquid to the liquid chamber;
With
A droplet discharge head, wherein a sheet-like heat generating means for heating the liquid in the common liquid chamber is disposed on an outer surface of at least a part of the outer wall of the common liquid chamber. A resin frame member that covers at least a part of the outer wall surface of the outer wall on which the heat generating means is disposed and constitutes a part of the outer wall of the common liquid chamber;
The thickness of the outer wall of the common liquid chamber in which the heat generating unit is disposed is 1/2 or less of the thickness of a frame member constituting the outer wall of the common liquid chamber. Droplet discharge head.   3. The droplet discharge head according to claim 1, wherein an outer wall of the common liquid chamber in which the heat generating unit is disposed is made of a thin metal plate member.   The droplet discharge head according to claim 1, wherein the metal thin plate member is integrally formed with the frame member by injection molding.   The droplet discharge head according to claim 1, wherein the heat generating unit is a film heater.   6. The liquid droplet ejection head according to claim 1, wherein the heat generating unit is bonded with a highly heat conductive adhesive.   A droplet discharge apparatus comprising: the droplet discharge head according to claim 1; and a tank that stores a liquid to be supplied to a common liquid chamber of the droplet discharge head. .   An image forming apparatus comprising the droplet discharge device according to claim 7.

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