JP2003266683A - Inkjet head and inkjet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet head which can improve an image quality and a jetting stability by reducing crosstalks between pressure liquid chambers. <P>SOLUTION: A fluid resistor 21 and the pressure liquid chamber 22 are graved in a channel plate 20, which communicate with a nozzle 31. A diaphragm 60 is driven by a laminate piezoelectric element (PZT) 50. A height of a partition wall, i.e., a height of the pressure liquid chamber 22 is set to be 70-120 μm and, a thickness of the channel plate 20 is set to be not smaller than twice the height of the partition wall. Accordingly, a pressure is prevented from increasing to not smaller than required, thereby suppressing take-in of bubbles caused by a residual pressure or a jetting decrease caused by vibrations of the partition wall and the channel plate 20. A dot position accuracy is improved, so that the image quality is improved. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head having a plurality of nozzles and an ink jet recording apparatus, and more particularly to an ink jet head in which an electromechanical conversion element such as a piezoelectric element is used to displace a vibration plate to eject ink droplets from the nozzle. TECHNICAL FIELD The present invention relates to an inkjet head that reduces crosstalk between adjacent pressurized liquid chambers, improves dot position accuracy, and improves image quality, and an inkjet recording apparatus using the inkjet head.

[0002]

2. Description of the Related Art An ink jet head in an ink jet recording apparatus used as an image forming apparatus such as a printer, a facsimile machine, a copying machine and a plotter, has a nozzle for ejecting ink droplets and a discharge chamber (pressure chamber, pressurizing chamber) communicating with the nozzle. (Also referred to as a liquid chamber, a liquid chamber, an ink chamber, an ink flow path, etc.) and actuator means for generating energy for pressurizing the ink in the discharge chamber, and the ink in the discharge chamber is driven by driving the actuator means. Is used to eject ink droplets from a nozzle, and the ink-on-demand method in which ink droplets are ejected only when recording is required is the mainstream.

Ink-on-demand type ink jet heads are classified into several types according to the type of actuator means for ejecting ink droplets (recording liquid). A thin diaphragm is used as a part of the wall of the liquid chamber, and a piezoelectric element as an electromechanical conversion element is arranged corresponding to this, and the diaphragm is deformed by the deformation of the piezoelectric element that occurs when a voltage is applied. Piezo type that changes the ink pressure in the chamber to eject ink droplets, a heating element is placed inside the liquid chamber, bubbles are generated by heating the heating element by energization, and ink droplets are ejected by the pressure of the bubbles The bubble jet (registered trademark) type is generally well known. In addition, a vibrating plate that forms the wall surface of the liquid chamber and an individual electrode outside the liquid chamber that is arranged so as to face the vibrating plate are provided, and static electricity generated by applying a voltage between the vibrating plate and the individual electrode is provided. There is also known an electrostatic type in which the vibration plate is deformed by electric power to change the pressure in the liquid chamber to eject ink droplets from the nozzle.

As a conventional example related to the present invention, Japanese Patent Laid-Open No.
Although the invention described in Japanese Patent Publication No. 1-993 is known,
According to the present invention, the height of the partition wall of the pressurized liquid chamber is set in the range of 100 to 160 μm in the electrostatic type or piezoelectric type inkjet head, from the viewpoint of the ink supply capability and the viewpoint of suppressing crosstalk and improving productivity. It is characterized by doing.

[0005]

In recent years, ink jet heads have tended to have a narrower nozzle pitch due to the demand for higher quality image quality, and as a result, the partition wall width of the pressurized liquid chamber is inevitably narrower. Has become. On the other hand, for high-speed printing, it is necessary to increase the ink ejection frequency, and for that purpose, it is necessary to shorten the ink filling (refill) time after ink ejection. In addition, in order to shorten the ink refill time, it is necessary to lower the fluid resistance value.
That is, it is necessary to increase the height of the partition wall. That is, the bulkhead of the pressurized liquid chamber tends to be narrower and higher,
Crosstalk easily occurs due to the influence of the adjacent pressurized liquid chamber.

Further, in the ink jet head described in JP-A No. 11-993, the height of the partition wall (height of the pressurized liquid chamber) is set to 100 to 160 μm so that the pressure from the adjacent pressurized liquid chamber is increased. Although crosstalk can be suppressed, actually, the crosstalk is not determined only by the height of the partition wall, but the influence varies depending on the width of the partition wall, the generated pressure, and the like. The lower limit of the height of the partition wall is 10
Regarding 0 μm, the reason is not clear because there is a description that the ink resistance value increases when the wall is low due to the ink supply capacity, and only the crosstalk due to the lateral vibration of the partition walls is a problem. The vertical vibration that pushes up the flow path plate forming the liquid chamber is not considered.

Accordingly, it is an object of the present invention to provide an ink jet head which can eliminate crosstalk between adjacent pressurized liquid chambers, improve image quality, and improve jetting stability. Another object of the present invention is to provide an ink jet recording apparatus which is equipped with the ink jet head and can obtain high quality image.

[0008]

The present invention has been made to solve the above problems, and the invention according to claim 1 is
A nozzle plate having a plurality of nozzles, a plurality of pressurized liquid chambers communicating with each of the nozzles and separated from each other by a partition wall, a flow path plate having an ink supply path, a vibration plate, and an electric machine for displacing the vibration plate. In the ink jet head having the conversion means, the height of the partition wall between the pressurized liquid chambers is 70 to 120 μm.
m, and the thickness of the flow path plate is at least twice the height of the partition wall.

According to a second aspect of the present invention, there is provided a nozzle plate having a plurality of nozzles, a plurality of pressurized liquid chambers communicating with each of the nozzles and separated from each other by a partition wall, and a flow path plate having an ink supply path, and a vibrating plate. And an ink jet head having electromechanical conversion means for displacing the vibrating plate, the partition wall between the pressurized liquid chambers has a height of 70 to 120 μm, and the electromechanical conversion means has a driving part and a supporting part. The partition wall is supported by the supporting unit via the diaphragm.

The invention according to claim 3 is the invention according to claim 1 or 2.
In the inkjet head described above, the compliance of the vibrating plate is smaller than the compliance due to the compression of the ink.

According to a fourth aspect of the present invention, in the ink jet head according to the first to third aspects, the ink droplets are ejected in the process of reducing the volume of the pressurized liquid chamber.

According to a fifth aspect of the present invention, there is provided a nozzle plate having a plurality of nozzles, a flow passage plate having a plurality of pressurized liquid chambers communicating with the respective nozzles and separated by partition walls, and an ink supply passage. A diaphragm and an electromechanical converting means for displacing the diaphragm are provided, and the height of the partition between the pressurized liquid chambers is 70 to 1
The thickness of the flow path plate is 20 μm, and the thickness of the flow path plate is an inkjet recording device having an inkjet head that is at least twice the height of the partition wall.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the embodiments shown in FIGS. Figure 1
FIG. 2 is a sectional view of a main part showing an embodiment of an inkjet head to which the present invention is applied, FIG. 2 is a sectional view taken along the line AA of FIG.
FIG. 3 is a sectional view taken along line BB in FIG. 1. The ink jet head of this embodiment is provided with an ink supply port 11 and a frame 10 in which a common liquid chamber 12 is engraved, and a fluid resistance portion 21, a pressurizing liquid chamber 22, and a communication port 23 communicating with the engraved nozzle. The formed flow path plate 20 and the plurality of nozzles 3
Nozzle plate 30 in which a nozzle row is formed by 1, a diaphragm 60 having a plurality of island-shaped convex portions (island portions) 61, a diaphragm portion 62, and an ink inlet 63;
The laminated piezoelectric element 50 joined to the island-shaped convex portion 61 via the adhesive layer 70, and the base 40 fixing the laminated piezoelectric element 50 are provided. The base 40 is made of barium titanate-based ceramic, and the laminated piezoelectric elements 50 are arranged and joined in two rows, and a similar inkjet head (not shown) is arranged on the laminated piezoelectric element on the left side of FIG. A nozzle row is formed.

The laminated piezoelectric element 50 includes a piezoelectric layer 51 of lead zirconate titanate (PZT) having a thickness of 10 to 50 μm per layer, and silver-palladium (AgPd) having a thickness of several μm per layer. And the internal electrode layers 52 of are alternately laminated, and the internal electrode layers 52 are connected to the external electrodes 53 at both ends.

As shown in FIG. 2, the laminated piezoelectric element 50 is divided into comb teeth by half-cut dicing. The pitch of the comb teeth is twice the pitch of the pressurized liquid chambers 22 formed in the flow path plate 20, and the comb teeth are alternately driven by the drive unit 5.
6 and the support portion 57 (non-driving portion). One of the external electrodes 53 (the external electrode 53 on the right side in FIG. 1) is arranged along the lower side in order to be completely divided when the laminated piezoelectric element 50 is divided into comb teeth by half-cut dicing. The cutout or the like is preliminarily processed so as to have a short length in the stacking direction of the stacked piezoelectric element 50, and after division, these become individual independent electrodes 54. The other external electrode 53 (the external electrode 53 on the left side in FIG. 1) is electrically connected without being divided by the dicing process.
It becomes 5. An FPC (flexible printed circuit) is provided on the individual electrode 54 connected to the driving unit 56 of the laminated piezoelectric element 50.
s) 80 is soldered. Further, the common electrode 55 is provided with an electrode layer at the end portion of the laminated piezoelectric element 50, and wraps around the laminated piezoelectric element 50 so that the ground electrode (Gn
It is joined to d). A driver IC (not shown) is mounted on the FPC 80, and the driver IC controls the application of the drive voltage to the individual electrode 54 of the drive unit 56.

The diaphragm 60 has a thin film diaphragm portion 62.
And a thick film portion including an island-shaped convex portion (island portion) 61 formed in the central portion of the diaphragm portion 62 and joined to the driving portion 56 of the laminated piezoelectric element 50, and a beam joined to the support portion 57 of the laminated piezoelectric element 50. Then, the opening serving as the ink inlet port 63 is formed by stacking two Ni plating films by the electroforming method. The diaphragm portion 62 has a thickness of 3 μm and a width of 35 μm (one side). The island-shaped convex portions 61 of the vibration plate 60, the drive unit 56 of the laminated piezoelectric element 50, and the vibration plate 60 and the frame 10 are bonded by patterning an adhesive layer 70 including a gap material.

The flow path plate 20 is made of a silicon single crystal substrate, and the fluid resistance portion 21, the engraved portion serving as the pressurized liquid chamber 22, and the through hole serving as the communication opening 23 at a position corresponding to the nozzle 31 are patterned by an etching method. It is formed. The portion left by etching becomes the partition wall 24 that separates the plurality of pressurized liquid chambers 22. Further, in this ink jet head, a portion for narrowing the etching width was provided and used as the fluid resistance portion 21.

The nozzle plate 30 is formed of a metal material, for example, a Ni plating film by an electroforming method, and has a large number of nozzles 31 which are fine ejection openings for ejecting ink droplets. Internal shape (inner shape) of this nozzle 31
Is shaped like a horn, but may be shaped like a cylinder or a truncated cone. The diameter of the nozzle 31 is about 20 to 35 μm on the ink droplet outlet side. The nozzle pitch of each row was 150 dpi.

The ink ejection surface (nozzle surface side) of the nozzle plate 30 is provided with a water repellent treatment layer 32 which is not shown and which is subjected to a water repellent surface treatment. PTFE-Ni eutectoid plating, electrodeposition coating of fluororesin, fluororesin with evaporative property (for example,
Stabilizes ink droplet shape and flight characteristics by providing a water repellent film selected according to the physical properties of the ink, such as those obtained by vapor deposition coating (fluoride pitch, etc.), baking after applying a silicone resin / fluorine resin solvent, etc. In order to obtain high quality image quality. The frame 10 forming the engraving that becomes the ink supply port 11 and the common liquid chamber 12 is made by resin molding.

In the thus constructed ink jet head, a driving waveform (pulse voltage of 10 to 50 V) is applied to the driving section 56 of the laminated piezoelectric element 50 in accordance with a recording signal, so that the driving section 56 is moved in the laminating direction. Displacement occurs, the pressurized liquid chamber 22 is pressurized through the vibrating plate 60, the ink pressure rises, and ink droplets are ejected from the nozzle 31. After that, when the ejection of the ink droplets is completed, the pressurized liquid chamber 22
The ink pressure in the inside decreases, a negative pressure is generated in the pressurized liquid chamber 22 due to the inertia of the ink flow and the discharge process of the driving pulse, and the process proceeds to the ink filling process. At this time, the ink supplied from the ink tank flows into the common liquid chamber 12 through the ink supply port 11, passes from the common liquid chamber 12 through the ink inflow port 63, the fluid resistance portion 21, and enters the pressurized liquid chamber 22. Is filled.

The fluid resistance portion 21 has an effect of damping the residual pressure vibration after ejection, but has resistance against ink refilling due to surface tension. By appropriately selecting the fluid resistance of the fluid resistance portion 21, it is possible to balance the attenuation of the residual pressure and the refill time, and to shorten the time (driving cycle) until the transition to the next ink droplet ejection operation.

(Explanation of Claim 1) In the invention of Claim 1, as shown in FIG. 2, the height H of the pressurized liquid chamber 22, that is, the partition 2
The height of No. 4 is set in the range of 70 to 120 μm. Drop velocity V when each inkjet head in the inkjet head is driven for each drive unit, that is, when each channel of inkjet head is driven
The magnitude of the crosstalk was determined by the difference ΔVj between j and the drop velocity Vj when multi-driving. The evaluated inkjet head had a partition wall height H of 50 to 150 μm,
The height H of the partition wall 24 (pressurized liquid chamber 22) is changed every 0 μm. Since the resistance value of the fluid resistance portion 21 changes depending on the height, the width is adjusted to have the same resistance value.

The driving conditions are as follows: when each ink jet head is driven (every one channel ink jet head) under stable conditions of constant frequency (f = 1 kHz),
A pulse voltage (to be precise, the rising and falling time constants are adjusted) that gives a drop velocity Vj = 7 m / s and a drop volume Mj = 18 pl is applied at a drive frequency f = 16 kHz. As a result, it was confirmed that ΔVj was within the range of ± 1 m / s in the inkjet head with the partition wall height H = 70 to 120 μm. ± 1 considering the dot position accuracy
The difference of m / s is the limit as the variation range of the drop velocity Vj.

When the height of the partition wall becomes higher than H = 130 μm in the ink jet head, the ejection state becomes unstable due to the influence of the residual vibration. In the ink jet head of H = 150 μm, the meniscus is broken and the nozzle surface is broken. The phenomenon of ink accumulation and jetting down (stopping) began to occur. This means that the mechanical vibrations of the partition wall 24 and the flow path plate 20 as a whole are not sufficiently damped by the flow damping mainly due to the fluid resistance represented by the fluid resistance portion 21.
If the pressure P is constant as in the following equation, the higher the partition wall height H is, the larger the partition lift amount ΔH due to the pressure becomes, and the flow path plate itself easily vibrates. From P∝ΔH / H, if P is constant, ΔH∝H. That is, also from this viewpoint, the height of the partition wall, that is, the height H of the pressurized liquid chamber is preferably 120 μm or less. Further, it is more preferable if it is less than 100 μm.

Further, in the ink jet head of H = 50-60 μm, although the ink is not accumulated on the nozzle surface, the phenomenon of jetting down, that is, jetting down due to so-called bubble drawing-in starts to occur. This is caused by the head recovery mechanism. When the ink is refilled by sucking the nozzle surface with a vacuum, the jetting down is eliminated, so that the bubble drawing is surely caused. However, when calculated from the ink viscosity, the ejection amount is such that ink can be refilled (refilled) sufficiently, and it is not the cause of insufficient ink supply due to high fluid resistance in the supply path such as the fluid resistance portion.

This will be described with reference to the pulse voltage waveform of FIG. The vibrating plate 6 is slightly different from the pressurized liquid chamber 22 depending on the design (resistance value, compliance, inductance ratio) of the fluid constants on the nozzle side / fluid resistance side.
0 displacement volume (excluded volume) ΔW and drop volume (dot diameter)
There is a strong correlation with Mj. Displacement volume ΔW of diaphragm 60
Is proportional to the displacement amount δ of the drive unit 56 of the laminated piezoelectric element 50, that is, the drive voltage Vp. That is, in order to eject the same (required) drop volume Mj, it is necessary to apply the same voltage Vp.

On the other hand, since the volume change rate ΔW / W (W: volume of the pressurized liquid chamber) is an index of pressure, the height of the pressurized liquid chamber H =
Since the volume of the pressurized liquid chamber of the inkjet head of 50 to 60 μm is smaller than that of the inkjet head of H = 90 μm, a pulse voltage with a steep rising edge suitable for the inkjet head of H = 90 μm as shown in FIG. When the voltage is applied, the pressure becomes too high, and violent bubble entrapment occurs due to residual vibration. Here, the drive voltage Vp cannot be changed due to the relationship with the liquid volume Mj, but since the droplet velocity Vj is sufficiently fast, a residual voltage is reduced by applying a pulse voltage having a gentle rise as shown in FIG. 4B. It is possible.

However, since the pressurized liquid chamber 22 has a Helmholtz resonance period Tc and the pressure oscillates, if the rise is longer than the half period Tc / 2 as shown in FIG. 4B, the pressure is canceled and the pressure is effective. Will not work. In addition, although it is considered that the pressure does not rise macroscopically, since there is a distribution in reality, there is a high pressure portion and it becomes unstable. Further, since the extra pressure is applied by the pressure that is lost due to the interference, the local pressure is further increased. The Form Hertz cycle of this example was Tc = 7 μs. From the above, when the height H of the pressurized liquid chamber is low, the residual pressure tends to be large and unstable, and the driving condition (Tc in this case) alone
Instability cannot be eliminated.

As described above, according to the present invention, not only the crosstalk due to the bending of the partition wall 24, but also the partition wall 24 and the flow path plate 20.
From the viewpoint of vibration and residual pressure, the height of the partition wall, that is, the height H of the pressurized liquid chamber is set in the range of 70 μm to 120 μm. This reduces crosstalk,
The dot position accuracy is improved and the image quality is improved. Also,
The stability is improved, and it is possible to suppress the occurrence of important problems such as injection down.

Since the flow path plate 20 is easily lifted, it is more effective for the ink jet head in which the partition wall 24 is not held by the support portion 57. Further, the actuator is not limited to the d33 type laminated piezoelectric element of the embodiment, and d
The same applies to an inkjet head using the 31 type.

In the first aspect of the invention, the thickness of the flow channel plate 20 is set to 400 μm. However, as the thickness of the flow channel plate 20 is reduced, bending vibration of the flow channel plate itself is not generated in the partition wall. It was found that the support would expand and contract, which promotes instability of the injection down. That is, it can be said that the flow path plate 20 needs to have a certain thickness with respect to the height of the partition wall 24, that is, the height H of the pressurized liquid chamber 22. As a result of an experimental study in which the thickness of the flow path plate 20 is reduced by polishing, the thickness of the flow path plate 20 is higher than the height H of the partition wall 24, that is, the height of the pressurized liquid chamber 22. It turns out that it is necessary to double the length.

When the thickness of the flow path plate 20 is smaller than this, the crosstalk due to the vibration of the flow path plate 20 becomes large even when the height of the pressurized liquid chamber is in the range of 70 to 120 μm, and the drop velocity Vj varies. Grows larger. When using multi-drive,
Due to the vibration of the flow path plate 20, the variation of Vj for each pressurized liquid chamber becomes large. This affects image quality. Further, since this mechanical vibration also vibrates the nozzle plate 30, a serious problem of jet down due to the generation of ink pools and the drawing of bubbles is likely to occur, and the margin of stability is small.

As in the present invention, the height of the partition wall between the pressurized liquid chambers is 70 to 120 μm, and the thickness of the flow path plate is the height H of the partition wall.
2 times or more, to suppress the vibration of the flow path plate itself, to prevent the deterioration of image quality due to crosstalk, and to widen the stability margin against the occurrence of serious problems that lead to jet down such as bubble drawing. You can

(Explanation of Claim 2) In this embodiment, the laminated piezoelectric element 50 is diced at a pitch twice as large as the pitch where the pressurized liquid chamber 22 is arranged, and the divided laminated piezoelectric element 50 is driven. The portions 56 and the supporting portions 57 are arranged alternately so that the partition walls 24 of the flow path plate 20 are supported via the portions between the island-shaped convex portions (island portions) 61 of the vibration plate. Yes (bi-pitch configuration). On the other hand, as an inkjet head, there is also an inkjet head having a structure in which the partition wall is not supported by a piezoelectric element, that is, a so-called normal pitch structure. In such a configuration, the partition wall 24 is supported by the frame 10 shown in FIG.

Focusing on the vibration of the flow path plate 20 as in the present invention, it is preferable to support the partition wall 24 by the bi-pitch structure as described above. That is, the present invention is directed to the partition wall 2
4 is supported by a bi-pitch structure to effectively operate, suppress vibration of the flow path plate 20 itself, prevent deterioration of image quality due to crosstalk, and stabilize stability against occurrence of a serious problem such as bubble drawing in which jetting down occurs. The margin can be widened.

(Explanation of Claim 3) In this embodiment, the compliance calculated from the thickness, width and material (Ni) of the diaphragm portion 62 of the diaphragm 60 is smaller than the compliance due to the compression of the ink. This is a result of the higher density nozzles. In such an inkjet head, since the pressure is not relaxed by the vibration plate, the pressure in the pressurized liquid chamber becomes high, and the problem of damping residual vibration as described above easily occurs.

On the other hand, since the pressure effectively acts on the ink, the driving efficiency is good and the low voltage driving is possible, and the compliance of the entire system is small so that the response is good and it is suitable for high-speed printing by high frequency driving. . That is, the present invention can provide a stable inkjet head with good responsiveness by adopting it to an inkjet head having a greater compliance due to ink compression than a compliance of a vibration plate.

(Explanation of Claim 4) In this embodiment, ink droplets are ejected in the process of reducing the volume of the pressurized liquid chamber from the initial state. The laminated piezoelectric element 50 of this embodiment is d33.
Since this is a system, the behavior of “pushing” in which the volume of the pressurized liquid chamber 22 is reduced when a voltage is applied and ink droplets are ejected is the basic operation.

Also in the case of "pulling", the height H of the pressurized liquid chamber
The pressure is optimized by, and the effect of suppressing mechanical vibration problems such as the vibration of the partition wall and the vibration of the entire flow path plate remains unchanged. The same applies to “pull-out” in which an intermediate potential is applied to the individual electrodes and ink drops are ejected by lowering the voltage in the same inkjet head structure, or “pull-out” to be performed using a d31 type actuator. However, since the hitting originally utilizes the pressure interference, the liquid volume Mj and the drop velocity Vj change due to the expansion / contraction timing of the pressurized liquid chamber, so that the effect of the present invention is not achieved.

By driving the ink jet head by pushing, the meniscus is ejected without being drawn in. Therefore, it is possible to easily eject droplets larger than the ejected ink. Further, the drop volume Mj (dot diameter) can be easily adjusted by the voltage. Further, in the case of the d33 type actuator, since the pushing impact does not require an intermediate potential, the drive circuit is simple and can be manufactured at low cost. However, the height H of the pressurized liquid chamber
If the above is not limited within the scope of the present invention, crosstalk that lifts the flow path plate is likely to occur, and the drop velocity Vj when multi-driving decreases. According to the present invention, by adopting the push-driving drive, it is possible to reduce the problem of flow path plate vibration and make the best use of the features of push-driving.

(Explanation of Claim 5) Next, an ink jet recording apparatus equipped with the ink jet head of the present invention will be explained. FIG. 5 is a perspective view showing an ink jet recording apparatus equipped with the ink jet head of the present invention, and FIG.
FIG. 6 is a cross-sectional view showing a mechanical portion of the inkjet recording apparatus of FIG. This inkjet recording apparatus includes a carriage 1 that is movable inside the recording apparatus main body 111 in the main scanning direction.
23, a printing mechanism 112 including a recording head 124 including an inkjet head according to the present invention mounted on a carriage 123, an ink cartridge 125 for supplying ink to the recording head 124, and the like, and below the recording apparatus main body 111. A paper feed cassette (or a paper feed tray) 114 capable of stacking a large number of papers 113 from the front side can be detachably attached to the section, and the papers 113 can be manually fed. The manual feed tray 115 can be opened and closed, the paper 113 fed from the paper feed cassette 114 or the manual feed tray 115 is taken in, a desired image is recorded by the printing mechanism unit 112, and then the paper ejected mounted on the rear surface side. The paper is discharged to the tray 116.

The printing mechanism 112 slides the carriage 123 in the main scanning direction (the direction perpendicular to the paper surface in FIG. 6) by the main guide rod 121 and the sub guide rod 122, which are guide members that are laterally mounted on the left and right side plates (not shown). A plurality of recording heads 124, which are freely held and are ejected to the carriage 123, eject ink droplets of respective colors of yellow (Y), cyan (C), magenta (M), and black (Bk). The ink ejection ports are arranged in a direction intersecting with the main scanning direction, and the ink droplet ejection direction is attached downward. Further, the recording head 1 is attached to the carriage 123.
Each ink cartridge 125 for supplying the ink of each color is exchangeably attached to the 24. The ink cartridge 125 has an upper atmosphere port communicating with the atmosphere, and a lower supply port supplying ink to the inkjet head.
The interior has a porous body filled with ink, and the ink supplied to the inkjet head is maintained at a slight negative pressure by the capillary force of the porous body.

Although the recording heads of the respective colors are used as the recording heads 124, a single head having nozzles for ejecting ink droplets of the respective colors may be used. here,
The carriage 123 is slidably fitted to the main guide rod 121 on the rear side (downstream side in the sheet conveying direction) and slidably mounted on the sub guide rod 122 on the front side (upstream side in the sheet conveying direction). . Then, in order to move and scan the carriage 123 in the main scanning direction, a timing belt 130 is stretched between the drive pulley 128 and the driven pulley 129 which are rotationally driven by the main scanning motor 127, and the timing belt 130 is mounted on the carriage 123. The carriage 123 is reciprocally driven by the forward and reverse rotations of the main scanning motor 127. On the other hand, in order to convey the paper 113 set in the paper feed cassette 114 to the lower side of the recording head 124,
The paper feed roller 131 and the friction pad 132 for separating and feeding the paper 113 from the paper feed cassette 114, and the paper 1
Guide member 133 for guiding 13 and the fed sheet 1
A transport roller 134 that inverts and transports 13 and a transport roller 135 that is pressed against the peripheral surface of the transport roller 134.
And a leading end roller 136 that defines the feed angle of the paper 113 from the transport roller 134. The conveyance roller 134 is rotationally driven by the sub-scanning motor 137 via a gear train.

The paper 1 sent from the carrying roller 134 in correspondence with the range of movement of the carriage 123 in the main scanning direction.
A print receiving member 139, which is a paper guide member for guiding the sheet 13 below the recording head 124, is provided. On the downstream side of the print receiving member 139 in the paper transport direction, the paper 113
Roller 1 that is driven to rotate in order to send out paper in the paper discharge direction
41 and a spur 142, and further, a paper discharge roller 143 and a spur 144 for sending the paper 113 to the paper discharge tray 116.
And guide members 145 and 146 that form a paper discharge path.

At the time of recording, by driving the recording head 124 in accordance with the image signal while moving the carriage 123, ink is ejected onto the stopped paper 113 to record one line, and the paper 113 is moved by a predetermined amount. After transportation, the next line is recorded. Upon receiving a recording end signal or a signal that the rear end of the paper 113 reaches the recording area, the recording operation is ended and the paper 113 is ejected. In this case, the recording head 1
The inkjet head according to the present invention, which constitutes 24,
Since the controllability of ink droplet ejection is improved and the characteristic variation is suppressed, it is possible to stably record an image of high image quality.

A recovery device 147 for recovering the ejection failure of the recording head 124 is arranged at a position outside the recording area on the right end side of the carriage 123 in the moving direction.
The recovery device 147 has a cap means, a suction means, and a cleaning means. The carriage 123 is moved to the recovery device 147 side while waiting for printing, and the recording head 124 is capped by the capping means, 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 an ejection failure occurs, the ejection port of the recording head 124 is sealed with a capping unit, and bubbles and the like are sucked from the ejection port with a suction unit through a tube and ink or dust adhered to the ejection port surface is cleaned. And the defective ejection is recovered. Further, the sucked ink is discharged to a waste ink reservoir (not shown) installed in the lower portion of the main body, and is absorbed and held by an ink absorber inside the waste ink reservoir.

As described above, by mounting the ink jet head which is the droplet discharge head according to the present invention,
Since stable ink droplet ejection characteristics can be obtained, it is possible to obtain a recording apparatus that can perform high-quality recording. The above inkjet recording apparatus has been described as a serial printer that discharges ink while a carriage equipped with an inkjet head moves in the main scanning direction. However, in the inkjet head of the present invention, the nozzle rows are linear in the main scanning direction. It is also possible to implement as a line printer which is arranged as described above and discharges ink in units of rows.

[0048]

As is apparent from the above description, the present invention has the following effects. In the inkjet head according to claim 1, since the height of the partition wall between the pressurized liquid chambers, that is, the height H of the pressurized liquid chambers is set in the range of 70 to 120 μm, crosstalk is small and dot positions are small. To improve stability by improving accuracy and improving image quality, suppressing excessive rise in pressure, making it difficult for air bubbles to be drawn in due to residual pressure and jet down due to vibration of partition walls and flow path plates to occur. You can Further, since the height of the partition wall is set in the range of 70 to 120 μm, and the thickness of the flow channel plate is set to be at least twice the height of the partition wall, that is, the height H of the pressurized liquid chamber, Suppress the vibration of itself,
It is possible to prevent deterioration of image quality due to crosstalk and widen the stability margin against a situation such as jetting down due to air bubble drawing.

In the ink jet head according to the second aspect, since the partition wall between the pressurized liquid chambers is supported by a part of the electromechanical transducer such as a piezoelectric element (bi-pitch structure), the flow path plate itself is formed. Vibration can be suppressed more effectively, deterioration of image quality due to crosstalk can be prevented, and a margin of stability can be widened against a situation such as air bubble entrainment that leads to jet down.

In the ink jet head according to the third aspect of the invention, since the compliance by the compression of the ink is larger than the compliance of the vibrating plate, the response is good and high-speed printing is possible, and the height of the partition wall, that is, the pressurized liquid. By limiting the height H of the chamber, it is possible to prevent deterioration of image quality due to crosstalk, and to widen the margin of stability against a situation such as air bubble entrainment that leads to jet down.

In the ink jet head according to the fourth aspect of the present invention, since the ejection of ink is performed by the pushing drive, the droplet volume Mj can be easily adjusted, a simple circuit configuration can be realized, and the height of the pressurized liquid chamber, that is, By limiting the height H of the partition wall, it is possible to prevent the deterioration of image quality due to crosstalk, and to widen the stability margin against a situation such as air bubble drawing that leads to jetting down.

In the ink jet recording apparatus according to the fifth aspect, by mounting the ink jet head according to the first aspect, it is possible to provide an ink jet recording apparatus having a high quality image.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of an inkjet head to which the present invention is applied.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG.

FIG. 4 is a diagram showing a pulse voltage waveform applied to a laminated piezoelectric element.

FIG. 5 is a perspective view showing an inkjet recording apparatus equipped with the inkjet head of the present invention.

6 is a cross-sectional view showing a mechanical portion of the inkjet recording apparatus of FIG.

[Explanation of symbols]

10 ... Frame, 11 ... Ink supply port, 12 ... Common liquid chamber, 20 ... Flow path plate, 21 ... Fluid resistance part, 22 ... Pressurized liquid chamber, 23 ... Communication port, 30 ... Nozzle plate, 31 ... Nozzle, 3
2 ... Water repellent treatment layer, 40 ... Base, 50 ... Laminated piezoelectric element,
51 ... Piezoelectric layer (PZT), 52 ... Internal electrode layer, 53 ... External electrode, 54 ... Individual electrode, 55 ... Common electrode, 56 ... Drive part, 57 ... Support part, 60 ... Vibrating plate, 61 ... Island-shaped convex part , 6
2 ... Diaphragm part, 63 ... Ink inlet, 70 ... Adhesive layer, 80 ... FPC, 111 ... Recording device main body, 112 ... Printing mechanism part, 113 ... Paper, 114 ... Paper feed cassette, 11
5 ... Manual feed tray, 116 ... Paper discharge tray, 121 ... Main guide rod, 122 ... Slave guide rod, 123 ... Carriage, 124 ... Recording head, 125 ... Ink cartridge, 127 ... Main scanning motor, 134 ... Conveying roller, 13
5, 141, 142 ... Transport rollers, 139 ... Printing receiving member.

Claims (5)

[Claims] 1. A nozzle plate having a plurality of nozzles, a plurality of pressurized liquid chambers communicating with each of the nozzles and separated from each other by a partition wall, a flow path plate having an ink supply path, a vibration plate, and the vibration plate. In the ink jet head having the electromechanical conversion means for displacing, the height of the partition wall between the pressurized liquid chambers is 70 to 120 μm, and the thickness of the flow path plate is at least twice the height of the partition wall. An inkjet head characterized in that there is. 2. A nozzle plate having a plurality of nozzles, a plurality of pressurized liquid chambers communicating with each of the nozzles and separated from each other by a partition wall, a flow path plate having an ink supply path, a vibration plate, and the vibration plate. In the ink jet head having the electromechanical conversion means for displacing, the height of the partition wall between the pressurized liquid chambers is 70 to 120 μm, the electromechanical conversion means has a drive part and a support part, and the partition wall is the An inkjet head, wherein the inkjet head is supported by a supporting portion via the diaphragm. 3. The ink jet head according to claim 1, wherein the compliance of the vibration plate is smaller than the compliance due to the compression of the ink. 4. The ink droplets are ejected in the process of reducing the volume of the pressurized liquid chamber.
The inkjet head according to any one of the above. 5. A nozzle plate having a plurality of nozzles, a plurality of pressurized liquid chambers communicating with each of the nozzles and separated from each other by a partition wall, and a flow path plate forming an ink supply path, a vibration plate, and the vibration plate. An ink jet head having electromechanical conversion means for displacing the partition wall, the height of the partition wall between the pressurized liquid chambers is 70 to 120 μm, and the thickness of the flow path plate is twice or more the height of the partition wall. An ink jet recording apparatus characterized by being equipped with.