JP2004299345A - Liquid droplet jet head and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that a structure for suppressing variation of a pressure in a common liquid chamber due to variation of a pressure in a pressurizing liquid chamber may be complex and the shape of the common liquid chamber may be limited. <P>SOLUTION: A part of a wall face of the common liquid chamber 8 is formed by a diaphragm member 2 for forming a wall face of the pressurizing liquid chamber 6. The part forming the wall face of the common liquid chamber 8 is made to be a free vibration face 21. The free vibration face 21 consists of a thick section 22 formed of a three-layer structure part of the three-layer structural diaphragm member 2 and a thin section 23 in a plane rectangular shape formed of a part in one-layer structure made by thinning the part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
[Industrial applications]
The present invention relates to a droplet discharge head and an image forming apparatus.
[0002]
[Prior art]
[Patent Document 1] Japanese Patent No. 3069477 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 7-171969 [Patent Document 3] Japanese Unexamined Patent Application Publication No. 9-141856 [Patent Document 4] Japanese Unexamined Patent Application Publication No. 2000-301714 [0003]
2. Description of the Related Art An ink jet recording apparatus used as an image forming apparatus such as a printer, a facsimile, a copying machine, and a plotter includes a nozzle for discharging ink droplets and a pressurized liquid chamber (ink flow path, discharge chamber, pressure chamber, pressurized chamber) communicating with the nozzle. And a pressure generating means (also referred to as a pressure converting means, an actuator means, a driving means, etc.) for pressurizing the ink in the pressurized liquid chamber. It is equipped with an ink jet head as a head. The droplet discharge head includes, for example, a droplet discharge head that discharges a liquid resist as droplets, a droplet discharge head that discharges a DNA sample as droplets, and the like, but the following description will focus on an inkjet head.
[0004]
As an inkjet head, as a pressure generating means that generates energy to pressurize the ink in the pressurized liquid chamber, an electromechanical transducer such as a piezoelectric element is used to deform the diaphragm that forms the wall of the ink flow path and pressurize. A so-called piezo type in which ink droplets are ejected by changing the volume of the liquid chamber, or a pressure generated by heating ink in the pressurized liquid chamber using a heating resistor (electrothermal converter) to generate bubbles. A so-called thermal type that discharges ink droplets, using an electrostatic actuator that deforms the diaphragm that forms the wall surface of the pressurized liquid chamber by electrostatic force, deforms the diaphragm to change the volume of the pressurized liquid chamber There is known an electrostatic type in which ink droplets are ejected.
[0005]
Major technical problems in the ink jet recording apparatus include speeding up and improving image quality. Methods for solving the problems include a method of increasing the driving frequency of the pressure generating means and a method of increasing the number of nozzles per head.
[0006]
However, when the driving frequency of the pressure generating means is increased, the behavior of the pressure in the pressurized liquid chamber becomes complicated due to the reflection of the pressure propagated from the pressurized liquid chamber to the common liquid chamber, and ink droplets are ejected accurately. It becomes difficult to do. Also, in such a head having a large number of nozzles, the shape may be narrowed at the longitudinal end of the common liquid chamber in order to improve the bubble discharge performance in the common liquid chamber. At the end in the hand direction, the pressure change is large, and the influence on the pressurized liquid chamber is greater than the central part in the longitudinal direction of the common liquid chamber, so that the pressure behavior differs depending on the position of the pressurized liquid chamber, all of which Is very difficult to control. Therefore, it is necessary to suppress the pressure change in the common liquid chamber and also suppress the difference in the pressure change depending on the position.
[0007]
Therefore, conventionally, as a configuration that suppresses pressure changes in the common liquid chamber,
As disclosed in Patent Literature 1, there is a method of providing an air damper by providing a gas chamber in a common liquid chamber. Also,
As disclosed in Patent Document 2, there is a method of absorbing a pressure generated by ejection by providing a foamable elastic material in at least a part of a liquid chamber.
[0008]
further,
As disclosed in Patent Document 3, a damper chamber is provided in a part of the common liquid chamber, and the damper chamber and the common liquid are held by a flexible material held between the pressurized liquid chamber and the energy generation unit. There is a method in which a flexible material is used as a damper by dividing a chamber. Also,
As disclosed in Patent Document 4, there is a method in which a flexible film including a piezoelectric element is provided in a common liquid chamber, and the piezoelectric element is driven according to the pressure of the common liquid chamber to absorb the pressure. .
[0009]
[Problems to be solved by the invention]
However, in the above-described conventional method disclosed in Patent Document 1, it is difficult to maintain the damper effect for a long period of time because the amount of air in the gas chamber does not recover by itself. Therefore, it is necessary to constantly control the amount of gas held in the gas chamber. However, there is a problem that it is difficult or expensive to implement with a head other than the electrothermal conversion type, for example, a heating element is required for that purpose. . In addition, it is difficult to control the amount of air in the gas chamber itself, and the air separated from the gas chamber enters the pressurized liquid chamber and cannot sufficiently increase the pressure in the pressurized liquid chamber. There is also a problem that may cause
[0010]
Also,
In the method of providing a foamable elastic material in a part of a liquid chamber as disclosed in Patent Literature 2, new processing for providing the foamable elastic material is required, resulting in an increase in cost. There are issues.
[0011]
further,
In the method of providing a damper chamber in a part of the common liquid chamber as disclosed in Patent Document 3, it is necessary to take a sufficient area of the damper chamber in order to sufficiently exhibit the damper effect. There is a problem in that the degree of freedom in the shape design of the common liquid chamber is reduced, and it becomes difficult to form a common liquid chamber having a bubble discharge property.
[0012]
Also,
In the method of providing a flexible film including a piezoelectric element in a common liquid chamber as disclosed in Patent Document 4, it is not possible to control the driving of the piezoelectric element in order to effectively absorb the pressure. However, there is a problem that the device becomes complicated and the cost increases, for example, it is difficult, and a control device for that purpose is newly required.
[0013]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a low-cost, low-cost droplet discharge head that improves droplet ejection characteristics, and an image forming apparatus including the droplet discharge head. With the goal.
[0014]
[Means for Solving the Problems]
In order to solve the above-described problems, a droplet discharge head according to the present invention has a configuration in which at least one wall surface of a common liquid chamber has a free vibration surface including a thick portion and a thin portion.
[0015]
Here, the free vibration surface is preferably formed integrally with a member forming the wall surface of the pressurized liquid chamber. Further, the free vibration surface preferably has a laminated structure composed of a plurality of layers. In this case, the thick portion of the free vibration surface preferably has the same thickness as the member forming the wall surface of the pressurized liquid chamber.
[0016]
The thin portion of the free vibration surface is preferably provided at or near a portion where the width of the free vibration surface in the short direction is narrow, or the thin portion of the free vibration surface is formed of a common liquid chamber. Is preferably provided corresponding to a portion where the cross-sectional area in the longitudinal direction is small or in the vicinity thereof.
[0017]
Further, it is preferable that the common liquid chamber has a small cross-sectional area at an end in the longitudinal direction.
[0018]
An image forming apparatus according to the present invention includes the droplet discharge head according to the present invention.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. An ink jet head according to a first embodiment of the droplet discharge head of the present invention will be described with reference to FIGS. 1 is an explanatory perspective view of the head for assembling, FIG. 2 is a cross-sectional explanatory view of the head along a lateral direction of the liquid chamber (along line AA in FIG. 1), and FIG. 3 is a long side of the liquid chamber of the head. FIG. 4 is an exploded perspective view of the head, and FIG. 5 is a schematic perspective view of the diaphragm of the head as viewed from the rear surface side thereof (along line BB in FIG. 1).
[0020]
This ink jet head has a channel plate 1 formed of a single crystal silicon substrate, a diaphragm member 2 joined to the lower surface of the channel plate 1, and a nozzle plate 3 joined to the upper surface of the channel plate 1. The pressurized liquid chamber 6 is an ink flow path through which the nozzles 4 for ejecting ink droplets, which are liquid droplets, communicate with each other through the nozzle communication path 5, and a common liquid chamber for supplying ink to the pressurized liquid chamber 6. An ink supply path 7 is formed as a fluid resistance portion that communicates with the ink passage 8 through an ink supply port 9.
[0021]
Further, pressure generating means (actuator means) for pressurizing the ink in the pressurized liquid chamber 6 corresponding to each pressurized liquid chamber 6 is provided on the outer surface side (the opposite side to the liquid chamber) of the vibration plate member 2. A laminated piezoelectric element 12 as an electromechanical conversion element is joined, and this piezoelectric element 12 is joined to a base substrate 13 formed of a highly rigid material such as metal or ceramics.
[0022]
Further, between the piezoelectric elements 12, support columns 14 are provided corresponding to the partition walls 1 a between the pressurized liquid chambers 6. Here, the piezoelectric element member is subjected to slit processing by half-cut dicing so as to be divided into a comb-tooth shape, and each of the piezoelectric element members is formed as a piezoelectric element 12 and a support portion 14. The strut portion 14 has the same configuration as the piezoelectric element, but is a simple strut since no drive voltage is applied.
[0023]
Further, the outer peripheral portion of the diaphragm member 12 is joined to the frame member 15 with an adhesive. The frame member 15 has a concave portion serving as the common liquid chamber 8 and an ink supply hole 16 (not shown) for supplying ink to the common liquid chamber 8 from outside (see FIG. 4). The frame member 15 is formed by injection molding of, for example, epoxy resin or polyphenylene sulphite.
[0024]
Here, the channel plate 1 is formed by anisotropically etching a single-crystal silicon substrate having, for example, a crystal plane orientation (110) using an alkaline etching solution such as an aqueous solution of potassium hydroxide (KOH), so that the nozzle communication passages 5, Although the pressurized liquid chamber 6 and the concave portion and the hole serving as the ink supply path 7 are formed, the present invention is not limited to a single crystal silicon substrate, and other stainless steel substrates and photosensitive resins can be used.
[0025]
The diaphragm 2 is formed from a nickel metal plate having a two-layer structure, and is manufactured by, for example, an electroforming method (electroforming method). It is also possible to use a laminated member or a laminated member of metal and metal (multilayer structural member).
[0026]
The nozzle plate 3 forms a nozzle 4 having a diameter of 10 to 35 μm corresponding to each pressurized liquid chamber 6 and is bonded to the flow path plate 1 with an adhesive. The nozzle plate 3 may be made of a metal such as stainless steel or nickel, a combination of a metal and a resin such as a polyimide resin film, silicon, or a combination thereof. Here, it is formed by a Ni plating film or the like by an electroforming method. Further, the inner shape (inner shape) of the nozzle 3 is formed in a horn shape (may be a substantially columnar shape or a substantially truncated cone shape), and the hole diameter of the nozzle 4 is about 20 to about the diameter on the ink droplet outlet side. It is 35 μm. Further, the nozzle pitch of each row was 150 dpi.
[0027]
In addition, a water-repellent treatment layer (not shown) that has been subjected to a water-repellent surface treatment is provided on the nozzle surface (surface in the discharge direction: discharge surface) of the nozzle plate 3. Examples of the water-repellent layer include PTFE-Ni eutectoid plating, electrodeposition coating of a fluororesin, evaporation-coated fluororesin (for example, pitch fluoride), silicon-based resin and fluorine-based resin. A water-repellent treatment film selected according to the physical properties of the ink, such as baking after the application of a solvent, is provided to stabilize the ink droplet shape and flying characteristics and obtain high-quality image quality.
[0028]
The piezoelectric element 12 alternately has a piezoelectric layer of lead zirconate titanate (PZT) having a thickness of 10 to 50 μm / 1 and an internal electrode layer of silver / palladium (AgPd) having a thickness of several μm / 1. The internal electrodes are alternately electrically connected to individual electrodes and common electrodes, which are end electrodes (external electrodes) on the end surfaces, and drive signals are supplied to these electrodes via the FPC cable 17. ing. The pressurized liquid chamber 6 is contracted and expanded by expansion and contraction of the piezoelectric element 12 whose piezoelectric constant is d23. When a drive signal is applied to the piezoelectric element 12 and charging is performed, the piezoelectric element 12 expands, and when the electric charge charged to the piezoelectric element 12 discharges, it contracts in the opposite direction.
[0029]
As shown in FIG. 4, the common liquid chamber 8 in the head has a planar shape and a rectangular shape in the arrangement direction of the pressurized liquid chambers 6 (nozzle arrangement direction, which is referred to as “the common liquid chamber longitudinal direction”). Has formed.
[0030]
Then, a part of the wall surface of the common liquid chamber 8 is formed by the vibration plate member 2 which is a member forming the wall surface of the pressurized liquid chamber 6, and the portion forming the wall surface of the common liquid chamber 8 is defined as a free vibration surface 21. I have. As shown in FIG. 5 (illustration of a joint portion of the piezoelectric element and the like is omitted), the free vibration surface 21 is a thick portion formed by a three-layer structure portion of the three-layer diaphragm member 2. 22 and a thin portion 23 having a rectangular shape in a plane and formed of a portion having a one-layer structure by removing a portion of the thickness. Here, the thick portion 22 and the thin portion 23 are arranged in a stripe shape in the longitudinal direction (nozzle arrangement direction) of the common liquid chamber. The thick part 22 may have a two-layer structure, the thin part 23 may have a one-layer structure, or the thick part 22 may have a three-layer structure, and the thin part 23 may have a two-layer structure.
[0031]
In the head configured as described above, by selectively applying a drive pulse voltage of 20 to 50 V to the piezoelectric element 12, the piezoelectric element 12 to which the pulse voltage is applied is displaced in the elongation direction and the pressurized liquid is applied. The portion of the diaphragm member 2 corresponding to the chamber 6 is deformed in the direction of the nozzle 4, and the ink in the pressurized liquid chamber 6 is pressurized by the volume / volume change of the pressurized liquid chamber 6, and the ink droplet is ejected from the nozzle 4. (Injection).
[0032]
Then, the liquid pressure in the pressurized liquid chamber 6 decreases with the ejection of the ink droplets, and a slight negative pressure is generated in the pressurized liquid chamber 6 due to the inertia of the ink flow at this time. In this state, by turning off the application of the voltage to the piezoelectric element 12, the diaphragm member 2 returns to the original position and the pressurized liquid chamber 6 has the original shape. appear. At this time, the ink is filled from the common liquid chamber 8 into the pressurized liquid chamber 6 via the ink supply port 9 and the ink supply path 7. Then, after the vibration of the ink meniscus surface of the nozzle 4 is attenuated and stabilized, a pulse voltage is applied to the piezoelectric element 12 for discharging the next ink droplet, and the ink droplet is discharged.
[0033]
Here, when the pressurized liquid chamber 6 is pressurized in order to eject ink droplets, a pressure wave generated in the pressurized liquid chamber 6 is transmitted to the common liquid chamber 8 via the fluid resistance portion 7 and the ink supply port 9. However, the pressure fluctuation in the common liquid chamber 8 is absorbed and attenuated by the thin portion 23 of the free vibration surface 21 forming the wall surface of the common liquid chamber 8, and the pressure wave is reflected to return to the pressurized liquid chamber 6. Is prevented. Thereby, the controllability of the meniscus and, consequently, the droplet ejection characteristics are improved.
[0034]
The results of the numerical simulation will be specifically described. When the wall surface of the common liquid chamber 8 is constituted by the diaphragm 2 itself (only the thick portion 22 is referred to as a comparative example), and in the above-described embodiment. As described above, the pressure change of the pressurized liquid chamber 6 corresponding to the center of the common liquid chamber 8 and the change of the common liquid chamber 8 A comparison was made with the pressure change in the pressurized liquid chamber 6 corresponding to the end.
[0035]
At this time, after applying a voltage to the piezoelectric element 12 to apply pressure to the pressurized liquid chamber 6 and averaging the effective value of the pressure change of the pressurized liquid chamber 6 for 20 μsec, In the case of the comparative example, the value in the pressurized liquid chamber 6 corresponding to the end portion was larger than that in the corresponding pressurized liquid chamber 6 by 15%. In this case, there was only a fluctuation of only 2%, and it was confirmed that the pressure absorption efficiency was increased by forming the free vibration surface 21 with the thin portion 23 and the thick portion 22.
[0036]
Furthermore, when a multi-injection experiment was performed for the comparative example and the example, it was confirmed that a defective image was generated in the comparative example, but no defective image was generated in the example.
[0037]
As described above, since at least one wall surface of the common liquid chamber has a free vibration surface including a thick portion and a thin portion, the pressure of the common liquid chamber is absorbed by the thin portion, and the free vibration surface is formed by the thick portion. The rigidity and strength of the common liquid chamber can be maintained, the pressure fluctuation in the common liquid chamber can be easily and effectively attenuated or absorbed, and the controllability of the meniscus and thus the injection characteristics can be improved. The degree of freedom in head design is improved, such as by improving air bubble discharge.
[0038]
That is, by having a free vibration surface in the common liquid chamber, the pressure in the common liquid chamber can be reduced by the damping effect, but the thinner the free vibration surface is, the higher the damping ability is. It is preferable to provide a thin free vibration surface on the entire wall surface of the chamber. However, it is difficult to form a thin film over a large area in terms of the method of construction and assembly, and there remains a problem in strength. Therefore, by providing a thick portion and a thin portion of the free vibration surface, it is easy to manufacture, the strength is sufficient, the damping effect can be obtained effectively, and the pressure in the common liquid chamber can be reduced. It becomes.
[0039]
In this case, by forming the free vibration surface as the same layer as the vibration plate arranged on one surface of the pressurized liquid chamber, the number of components of the head can be reduced, and the vibration plate and the free vibration surface can be combined. It is possible to form them simultaneously in the same process.Furthermore, after forming the components that make up the pressurized liquid chamber and the parts that make up the common liquid chamber, the pressurized liquid The chamber section and the common liquid chamber section can be formed, and the manufacturing cost, the number of manufacturing steps, the number of assembling steps, and the like can be reduced.
[0040]
Further, by forming the free vibration surface into a laminated structure, a thin portion can be easily formed by changing the number of layers. Further, by making the thick portion the same thickness as the maximum thickness of the diaphragm, a free vibration surface which is easy to manufacture and has high strength can be formed.
[0041]
Next, a second embodiment of the droplet discharge head according to the present invention will be described with reference to FIGS. FIG. 6 is an exploded perspective view of the head, and FIG. 7 is a schematic perspective view of the diaphragm of the head viewed from the back side.
Here, a thin portion 23 is provided around a free vibration surface 21 forming the wall surface of the common liquid chamber 8, and an island-shaped thick wall 22 is formed at the center of the free vibration surface 21.
[0042]
Here also, a defective image occurred in the printing test in the multi-ejection with the head having no thin portion, but in the multi-ejection with the head according to the present invention in which the free vibration surface was formed by the thin portion and the thick portion. In the printing test, good results were obtained without occurrence of a defective image.
[0043]
Next, a third embodiment of the droplet discharge head according to the present invention will be described with reference to FIGS. 8 is an exploded perspective view of the head, and FIG. 9 is a schematic perspective view of the diaphragm of the head viewed from the back side.
Here, while one thick portion 22 is provided in the second embodiment, two thin portions 23 separated in the longitudinal direction of the common liquid chamber on a free vibration surface 21 forming the wall surface of the common liquid chamber 8, By providing the island-shaped thick portions 22, 22 by providing 23, the strength is improved as compared with the second embodiment.
[0044]
In this case as well, a defective image occurred in the printing test in the multi-ejection using the head having no thin portion. In the printing test, good results were obtained without occurrence of a defective image.
[0045]
Next, a fourth embodiment of a droplet discharge head according to the present invention will be described with reference to FIGS. 10 is an exploded perspective view of the head, and FIG. 11 is a schematic perspective view of the diaphragm of the head viewed from the back side.
In this head, the common liquid chamber 8 is formed to have a shape in which the width in the short direction becomes narrow and the depth becomes shallow at the longitudinal end 8a, so that the air bubbles are easily discharged. The free vibration surface 21 is formed with thin portions 23, 23 having a planar shape conforming to the shape of the common liquid chamber at the longitudinal end 8a of the common liquid chamber 8.
[0046]
Here also, a defective image occurred in the printing test in the multi-ejection with the head having no thin portion, but in the multi-ejection with the head according to the present invention in which the free vibration surface was formed by the thin portion and the thick portion. In the printing test, good results were obtained without occurrence of a defective image.
[0047]
As described above, by providing the thin portion 23 in a portion (or in the vicinity thereof) where the width of the free vibration surface 21 in the short side direction of the common liquid chamber is reduced, it is possible to effectively suppress and attenuate the pressure fluctuation. it can. In other words, since the damping ability of the flat plate is almost proportional to the cube of the length, when the free vibration surface 21 is a flat plate (when the thin portion 23 is not provided), the width of the free vibration surface 21 in the width direction is small. The damping ability is greatly reduced in the narrow portion. Therefore, by providing the thin portion 23 at or near the portion where the width of the free vibration surface 21 in the short direction is reduced, the pressure of the common liquid chamber can be effectively reduced.
[0048]
In addition, by narrowing the shape toward the end of the common liquid chamber 8, the flowability of the ink is improved, and the pressure of the common liquid chamber is effectively reduced while improving the bubble discharging property. Becomes possible.
[0049]
That is, when the cross-sectional area of the common liquid chamber in the longitudinal direction is small and the width of the free vibration surface in the short direction is also small, the damping ability is also reduced. Therefore, it is difficult to reduce the cross-sectional area of the common liquid chamber in the longitudinal direction because the influence is large.
[0050]
However, as described above, the pressure in the common liquid chamber can be effectively reduced by providing the thin portion 23 on the free vibration surface at or near a portion where the cross-sectional area in the longitudinal direction of the common liquid chamber 8 is small. Therefore, the shape of the common liquid chamber 8 is reduced toward the end so that the cross-sectional area is reduced, so that the ink flowability is improved. become.
[0051]
Next, an example of an inkjet recording apparatus, which is an image forming apparatus according to the present invention, on which an inkjet head, which is a droplet discharge head according to the present invention, is described with reference to FIGS. FIG. 12 is a configuration diagram illustrating the overall configuration of an ink jet recording apparatus as an image forming apparatus according to the present invention, and FIG. 13 is a schematic plan view of a main part of the recording apparatus.
[0052]
In this ink jet recording apparatus, a carriage 103 is slidably held in a main scanning direction by a guide rod 101 and a stay 102 which are guide members which are laterally mounted on left and right side plates (not shown), and a timing belt 105 is moved by a main scanning motor 104. 22 is moved and scanned in the direction indicated by the arrow (main scanning direction) in FIG.
[0053]
The carriage 103 includes four inkjet heads, which are droplet ejection heads according to the present invention, which eject ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk). The recording head 107 has a plurality of ink ejection ports arranged in a direction crossing the main scanning direction, and is mounted with the ink droplet ejection direction facing downward.
[0054]
The carriage 103 is mounted with sub-tanks 108 of each color for supplying each color ink to the recording head 107. The sub tank 108 is supplied with ink from a main tank (ink cartridge) via an ink supply tube (not shown).
[0055]
On the other hand, as a paper feeding unit for feeding paper 112 loaded on a paper loading unit (pressing plate) 111 such as a paper feed cassette 110, a half-moon roller that separates and feeds the papers 112 one by one from the paper loading unit 111 ( A sheet feeding roller 113 and a separation pad 114 made of a material having a large coefficient of friction are provided to face the sheet feeding roller 113, and the separation pad 114 is urged toward the sheet feeding roller 113.
[0056]
As a transport unit for transporting the paper 112 fed from the paper feed unit below the recording head 107, a transport belt 121 for electrostatically attracting and transporting the paper 112, and a feed belt 121 A counter roller 122 for transporting the paper 112 fed via the guide 115 between the transport belt 121 and the paper 112 transported substantially vertically upward is turned by approximately 90 ° to copy the paper 112 onto the transport belt 121. A transport guide 123 for adjusting the pressure and a pressing roller 125 urged toward the transport belt 121 by a pressing member 124 are provided. Further, a charging roller 126 serving as a charging unit for charging the surface of the transport belt 121 is provided.
[0057]
Here, the transport belt 121 is an endless belt, is stretched between a transport roller 127 and a tension roller 128, and is transported from a sub-scanning motor 131, which is an electric motor, via a timing belt 132 and a timing roller 133. It is configured to rotate in the direction indicated by the arrow (belt conveyance direction) by rotating 127.
[0058]
The transport belt 121 has a surface layer 21a serving as a sheet adsorption surface formed of a pure resin material having a thickness of about 40 μm, for example, of which the resistance is not controlled, for example, ETFE pure material, and performs resistance control using carbon with the same material as the surface layer. Back layer (medium resistance layer, earth layer).
[0059]
The charging roller 126 is arranged so as to be in contact with the surface layer of the conveyor belt 121 and rotate following the rotation of the conveyor belt 21, and apply 2.5 N to both ends of the shaft as a pressing force. The transport roller 127 also serves as an earth roller, and is arranged in contact with the middle resistance layer (back layer) of the transport belt 121 and is grounded.
[0060]
A guide member 136 is arranged on the back side of the transport belt 21 so as to correspond to a printing area of the recording head 4. The guide member 136 has an upper surface protruding toward the recording head 107 beyond a tangent line between two rollers (the transport roller 127 and the tension roller 128) supporting the transport belt 121. As a result, the transport belt 121 is pushed up and guided by the upper surface of the guide member 136 in the printing area.
[0061]
Further, as a paper discharge unit for discharging the paper 112 recorded by the recording head 107, a separation unit for separating the paper 112 from the transport belt 121, a paper discharge roller 142 and a paper discharge roller 143, and a paper discharge And a discharge tray 144 for storing the sheets 112 to be printed. A duplex paper supply unit 151 is detachably mounted on the back. The double-sided paper supply unit 151 takes in the paper 112 returned by the rotation of the transport belt 121 in the reverse direction, reverses the paper 112, and feeds the paper 112 again between the counter roller 122 and the transport belt 121.
[0062]
In the ink jet recording apparatus thus configured, the paper 112 is fed separately from the paper feeding unit one by one, and the paper 112 fed substantially vertically upward is guided by the guide 115, and the conveyance belt 121 and the counter roller 122 Are transported, and the leading end thereof is guided by a transport guide 123, pressed against the transport belt 121 by a tip pressing roller 125, and the transport direction is changed by approximately 90 °.
[0063]
At this time, a positive output and a negative output are alternately repeated from the high voltage power supply to the charging roller 126 by the control circuit (not shown), that is, an alternating voltage is applied, and the charging voltage pattern in which the transport belt 121 alternates, that is, In the sub-scanning direction, which is the circling direction, plus and minus are alternately charged in a belt shape with a predetermined width. When the paper 112 is fed onto the positively and negatively charged conveyor belt 121, the paper 112 is polarized in the paper 112 to a charge opposite to the charged pattern, so that a capacitor connected in parallel is formed. The sheet 112 is attracted to the conveyor belt 121, and the paper 112 is conveyed in the sub-scanning direction by the orbital movement of the conveyor belt 121.
[0064]
Therefore, by driving the recording head 107 according to the image signal while moving the carriage 103, ink droplets are ejected onto the stopped paper 112 to record one line, and after the paper 112 is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal indicating that the rear end of the sheet 112 has reached the recording area, the recording operation ends, and the sheet 12 is discharged to the discharge tray 144.
[0065]
As described above, since the ink jet recording apparatus includes the ink jet head which is the droplet discharge head according to the present invention, pressure fluctuation of the common liquid chamber is suppressed, and stable ejection characteristics can be obtained. Image quality recording can be performed.
[0066]
In the above-described embodiment, an example of an inkjet recording apparatus including the inkjet head is described as applied to an inkjet head as a droplet discharge head. The invention can be applied to other droplet ejection heads such as a droplet ejection head that ejects droplets, a droplet ejection head that ejects a DNA sample as droplets, and can be applied to an image forming apparatus other than an inkjet recording apparatus.
[0067]
【The invention's effect】
As described above, according to the droplet discharge head of the present invention, at least one wall surface of the common liquid chamber has a free vibration surface composed of a thick part and a thin part, so that the pressure of the common liquid chamber is Fluctuations can be effectively suppressed and attenuated, the ejection characteristics of the droplets are improved, and the size and cost of the head can be reduced.
[0068]
According to the image forming apparatus of the present invention, since the image forming apparatus includes the droplet discharge head of the present invention, high-quality recording can be performed.
[Brief description of the drawings]
FIG. 1 is an explanatory perspective view of a droplet discharge head according to a first embodiment of the present invention in an assembled state; FIG. 2 is a cross-sectional explanatory view of the head along a liquid chamber longitudinal direction; FIG. FIG. 4 is an exploded perspective view of the head. FIG. 5 is a schematic perspective view of the diaphragm of the head viewed from the back side. FIG. 6 is a droplet according to the present invention. Exploded perspective view illustrating a second embodiment of a discharge head. FIG. 7 is a schematic perspective view illustrating a diaphragm of the head viewed from the back surface. FIG. 8 is a third embodiment of a droplet discharge head according to the present invention. FIG. 9 is a schematic perspective view illustrating a diaphragm of the head viewed from the back side. FIG. 10 is an exploded perspective view illustrating a droplet discharge head according to a fourth embodiment of the present invention. FIG. 11 is a schematic perspective explanatory view of the diaphragm of the head viewed from the back side. FIG. 12 is an image according to the present invention. Main part schematic plan view of a schematic diagram 13 the recording apparatus showing an example of an ink jet recording apparatus as deposition apparatus [Description of symbols]
DESCRIPTION OF SYMBOLS 1 ... Flow path plate, 2 ... Vibrating plate member, 3 ... Nozzle plate, 4 ... Nozzle, 6 ... Pressurized liquid chamber, 7 ... Ink supply path, 8 ... Common liquid chamber, 12 ... Piezoelectric element, 21 ... Free vibration surface , 22 ... thick part, 23 ... thin part.

Claims (8)

In a droplet discharge head including a plurality of pressurized liquid chambers to which nozzles for discharging liquid droplets communicate, and a common liquid chamber for supplying liquid to the plurality of pressurized liquid chambers, at least one wall surface of the common liquid chamber Characterized by having a free vibration surface comprising a thick portion and a thin portion. 2. The droplet discharge head according to claim 1, wherein the free vibration surface is formed integrally with a member forming a wall surface of the pressurized liquid chamber. 3. The droplet discharge head according to claim 1, wherein the free vibration surface has a laminated structure including a plurality of layers. 3. The droplet discharge head according to claim 2, wherein the thick portion of the free vibration surface has the same thickness as a member forming a wall surface of the pressurized liquid chamber. 5. The droplet discharge head according to claim 1, wherein the thin portion of the free vibration surface is provided at or near a portion where the width of the free vibration surface in the lateral direction is narrow. A droplet discharge head characterized in that: 6. The droplet discharge head according to claim 1, wherein the thin portion of the free vibration surface is provided corresponding to a portion of the common liquid chamber having a small cross-sectional area in a longitudinal direction or in the vicinity thereof. A droplet discharge head characterized in that: 7. The droplet discharge head according to claim 1, wherein the common liquid chamber has a reduced cross-sectional area at an end in a longitudinal direction. An image forming apparatus for forming an image by discharging droplets from a droplet discharge head, wherein the droplet discharge head is the droplet discharge head according to any one of claims 1 to 7. apparatus.

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