JP2015147341A - Ink jet head, manufacturing method of ink jet head, and ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet head which reduces air bubbles and foreign objects, inhibits pressure fluctuation, controls the injection quantity, inhibits drive frequency drop, and improves the durability by using a small and simple structure achieving low cost without providing additional mechanisms.SOLUTION: An ink jet head 21 includes a body substrate 41, in which a main chamber 41a communicating with an ink supply port 45 and a nozzle hole 32a is formed, and injects an ink in the main chamber 41a from the nozzle hole 32a. An auxiliary chamber 41b driven independently of the main chamber 41a and a communication part 41c allowing the main chamber 41a and the auxiliary chamber 41b to communicate with each other are formed in the body substrate 41 in which the main chamber 41a is formed. The auxiliary chamber 41b is positioned at the outer side of an ink passage forming from the ink supply port 45 to the nozzle hole 32a through the main chamber 41a in the body substrate 41.

Description

  The present invention relates to an inkjet head that ejects ink in a main chamber formed on a substrate from a nozzle hole, a method for manufacturing the inkjet head, and an inkjet printer that includes the inkjet head.

  2. Description of the Related Art Conventionally, an ink jet printer including an ink jet head having a plurality of channels for ejecting liquid ink is known. By controlling the ejection of ink while moving the inkjet head relative to a recording medium such as paper or cloth, a two-dimensional image can be output to the recording medium. Ink can be ejected by using a pressure actuator (piezoelectric, electrostatic, thermal deformation, etc.) or by generating bubbles in the ink inside the tube by heat. Among them, the piezoelectric actuator has advantages such as high output, modulation, high responsiveness, and choice of ink, and has been frequently used in recent years.

There are two types of piezoelectric actuators: one that uses a bulk piezoelectric material that fires like a ceramic tile, and one that uses a thin film piezoelectric material (piezoelectric thin film) that is deposited on a substrate. It is selected appropriately according to. Perovskite-type metal oxides such as barium titanate (BaTiO ₃ ) and lead zirconate titanate (Pb (Ti / Zr) O ₃ ) are widely used for piezoelectric bodies used in piezoelectric actuators.

  FIG. 11 is a plan view showing a schematic configuration of an inkjet head 100 using a conventional piezoelectric actuator, and a cross-sectional view taken along line a-a ′ in the plan view. In the inkjet head 100, a plurality of channels 101 for ejecting ink are two-dimensionally arranged. Such an ink jet head 100 is roughly composed of a body 201 and a nozzle 202.

  FIG. 12 shows a plan view of one channel 101 of the inkjet head 100 and a cross-sectional view taken along the line b-b ′ in the plan view. The body 201 is roughly composed of a body substrate 301 and an actuator 302, and the nozzle 202 is composed of a nozzle substrate 303 having a nozzle hole 303a for controlling the droplet amount. The actuator 302 is disposed on one surface side of the body substrate 301, and the nozzle substrate 303 is disposed on the other surface side.

  The body substrate 301 is formed with a pressure chamber 301a for containing ink. The pressure chamber 301 a communicates with the nozzle hole 303 a of the nozzle substrate 303. The actuator 302 has at least two layers of a follower plate that does not displace and a piezoelectric member that displaces. More specifically, the actuator 302 is configured by laminating a driven plate 401, an insulating film 402, a lower electrode 403, a piezoelectric body 404, and an upper electrode 405 in order from the body substrate 301 side. The lower electrode 403 and the upper electrode 405 are connected to the drive circuit 406.

  In the above structure, when a voltage is applied from the drive circuit 406 to the lower electrode 403 and the upper electrode 405, the piezoelectric body 404 expands and contracts in a direction perpendicular to the thickness direction. Then, due to the difference in length between the piezoelectric body 404 and the driven plate 401, a curvature is generated in the driven plate 401, and the driven plate 401 is displaced (curved) in the thickness direction. By such vertical movement of the actuator 302, pressure can be applied to the ink in the pressure chamber 301a to eject ink droplets from the nozzle hole 303a.

  The pressure chamber 301a communicates with an ink supply port 302a formed in the actuator 302, and ink is supplied to the pressure chamber 301a from a tank (not shown) through the ink supply port 302a.

  Thus, one channel 101 is configured by combining the actuator 302, the pressure chamber 301a formed in the body substrate 301, and the nozzle hole 303a formed in the nozzle substrate 303. The ink jet head 100 is configured by arranging the channels 101 vertically and horizontally.

[About bubbles and foreign objects]
By the way, if bubbles exist in the pressure chamber, the force of the actuator is not transmitted to the ink in the pressure chamber, and ink ejection failure occurs. As the cause of the presence of bubbles in the pressure chamber, for example, the following can be considered.
(A) Bubbles are mixed in the ink supplied to the pressure chamber.
(B) Bubbles remain in the pressure chamber when ink is introduced into the pressure chamber.
(C) Since the pressure chamber is in a negative pressure state after ink is ejected from the nozzle holes, bubbles are generated in the ink due to cavitation (cavity phenomenon).

In addition, if foreign matter such as dust or aggregates is present in the pressure chamber, the foreign matter is clogged in the nozzle hole and ink ejection failure occurs. As a cause of the presence of foreign matter in the pressure chamber, for example, the following can be considered.
(D) Foreign matter generated during processing or assembly is present inside the head.
(E) The ink itself supplied to the pressure chamber contains foreign matter.

Conventionally, the following methods have been proposed as countermeasures against bubbles and foreign matters.
(1-1) A foreign substance and air bubbles are removed by a deaeration mechanism using a filter or a hollow fiber.
(1-2) An oscillating portion is provided in the flow path to reduce adverse effects due to bubbles. For example, in Patent Document 1, an ink flow is generated by a vibrating portion provided on the upstream side of the pressure chamber, thereby preventing the upstream inlet of the pressure chamber from being blocked by bubbles and causing ejection failure. ing.
(1-3) Circulating ink to discharge bubbles and foreign matters. For example, in Patent Document 2, two sets are prepared by attaching a cover substrate to a channel substrate in which channel grooves are formed, and using the channel grooves as pressure chambers. The pressure chambers and the connection flow paths are connected by bonding the connection substrates having the connection flow paths to the end portions of the flow path substrates and bonding the connection flow paths to each other. The flow path is formed.

[Pressure fluctuation and injection amount control]
When the pressure of the ink supplied to the pressure chamber fluctuates, the ejection performance (ink ejection amount and ejection speed) varies even if the actuator force is constant. Possible causes of fluctuations in ink pressure are as follows, for example.
(F) The liquid level of the ink tank fluctuates according to the residual amount of ink, so that the pressure of the supplied ink fluctuates.
(G) In the method of printing by scanning the head with respect to the paper surface, the pressure of the supplied ink varies depending on the movement acceleration of the head during scanning and the distance from the tank.
(H) In a system in which a head having a length corresponding to the paper width is fixed and arranged, and the paper is wound around a cylindrical drum for printing, the pressure of the supplied ink depends on the head mounting angle (downward, sideways, etc.) Fluctuates.

  Further, depending on the specifications of the apparatus, it may be necessary to control the shading of one pixel. For example, when the image is darkened, when a thick line is drawn, or when the amount of liquid in the adjacent channel is small, it is necessary to increase the ink ejection amount. On the other hand, when thinning the image or drawing a thin line, it is necessary to reduce the ink ejection amount.

Conventionally, the following methods have been proposed for suppressing pressure fluctuation and controlling the injection amount.
(2-1) Apply pressure with a pump or stabilize pressure in a spare chamber.
(2-2) A plurality of piezoelectric elements are provided in one pressure chamber to adjust the pressure in the pressure chamber (see Patent Document 3).
(2-3) General-purpose methods such as changing the drive voltage and increasing / decreasing the number of injections.

JP-A-5-293971 (see claim 1, paragraphs [0029], [0066], [0067], FIG. 2, etc.) JP 2007-175922 A (refer to paragraphs [0034] to [0041], FIG. 3, FIG. 4 etc.) Japanese Patent No. 3006577 (see claim 1, paragraphs [0034] and [0035], FIG. 1 and FIG. 2)

  However, with respect to the removal of bubbles and foreign substances, suppression of pressure fluctuations, and injection amount control, the conventional measures described above have the following problems.

(About 1-1 and 2-1)
In the configuration in which a deaeration mechanism, a pump, and a spare chamber are provided outside, the apparatus is increased in size and cost.

(About 1-2)
In Patent Document 1, the vibration part is provided in series with the pressure chamber. However, since the vibration part is on the upstream side of the pressure chamber, there is no effect on the bubbles generated and accumulated in the pressure chamber on the downstream side. The air bubbles in the pressure chamber cannot be removed.

(About 1-3)
Since Patent Document 2 has a configuration in which ink is circulated across a plurality of substrates (channel substrates, connection substrates), there is a concern that the configuration is complicated and the apparatus becomes large.

(About 2-2)
In a configuration in which a plurality of piezoelectric elements are provided in one pressure chamber as in Patent Document 3, the volume of the pressure chamber is increased, so that the drive frequency of the piezoelectric element is decreased. That is, when the volume of the pressure chamber (corresponding to m described above) increases from the relationship of the equation of motion F = ma (F: force applied to the object, m: mass of the object, a: acceleration generated in the object), the piezoelectric element causes When the generated force (corresponding to F above) is constant, the acceleration when the ink in the pressure chamber moves decreases. This is the same as a decrease in the driving frequency of the piezoelectric element.

(About 2-3)
When the driving voltage is increased or the number of injections is increased, the durability of the head is lowered.

  The present invention has been made to solve the above-mentioned problems, and its purpose is to eliminate bubbles and foreign substances and to suppress pressure fluctuations with a small, low-cost and simple configuration without providing an additional mechanism. It is another object of the present invention to provide an ink jet head that can perform ejection amount control, suppress a decrease in driving frequency, and improve durability, a manufacturing method thereof, and an ink jet printer including the ink jet head.

  An inkjet head according to an aspect of the present invention is an inkjet head that includes a substrate on which a main chamber communicating with an ink supply port and a nozzle hole is formed, and ejects ink in the main chamber from the nozzle hole. The substrate in which the chamber is formed is formed with a sub chamber that is driven independently of the main chamber, and a communication portion that communicates the main chamber with the sub chamber. The substrate is positioned outside the ink flow path from the ink supply port to the nozzle hole through the main chamber.

  The substrate is formed with a main chamber, a sub chamber, and a communication portion that communicates the main chamber, and the sub chamber is driven independently of the main chamber. In this configuration, for example, by driving only the main chamber, the ink in the main chamber can be ejected from the nozzle holes. In addition, by driving only the sub chamber, ink can be circulated between the main chamber and the sub chamber via the communication portion, and bubbles and foreign matters in the main chamber can be removed. In particular, the sub chamber is not in series with the main chamber in the substrate (not in the ink flow path from the ink supply port to the nozzle hole through the main chamber), but in parallel with the main chamber, that is, the ink flow path. Therefore, bubbles and foreign matters generated in the main chamber or bubbles and foreign matters flowing into the main chamber can be effectively removed.

  In addition, for example, the main chamber and the sub chamber are driven simultaneously, and by controlling the sub chamber, the pressure in the main chamber is made constant (pressure fluctuation is suppressed), and the amount of ink ejected from the nozzle holes is controlled. It becomes possible to do. In addition, by independently driving the main chamber and the sub chamber, the ink ejection amount can be controlled without increasing the driving voltage or increasing the number of ejections, so that the durability of the head can be improved.

  In addition, since the main room and the sub chamber are not directly communicated with each other via the communication part, these rooms can be substantially divided by the flow path resistance of the communication part. And it can suppress that the volume of a main chamber increases substantially by providing a subchamber. Thereby, it can suppress that the drive frequency of a main chamber falls, and can implement | achieve high-speed drive.

  In addition, since the main chamber, sub chamber, and communication portion are formed on the same substrate, there is no need to add an external mechanism for suppressing ink circulation and pressure fluctuation, and the size, cost, and simpleness are eliminated. With the configuration, the above-described effects can be obtained. In particular, since the circulation of ink can be realized in the same substrate, the configuration of the head is surely simplified and the enlargement of the head can be surely avoided as compared with the conventional configuration in which the ink is circulated across a plurality of substrates.

  The inkjet head may include a driving unit that drives the main chamber and the sub chamber independently. The drive unit can drive only the main chamber, only the sub chamber, or both the main chamber and sub chamber, so that the above-described ink circulation, ink ejection amount control, etc. can be ensured. It can be carried out.

  The drive unit may circulate ink between the main chamber and the sub chamber via the communication unit by driving the sub chamber when ink is not ejected from the main chamber. When the ink is not ejected, the sub chamber is driven to circulate the ink, thereby removing bubbles and foreign matters in the main chamber.

  It is desirable that the main chamber and the sub chamber communicate with each other via a plurality of the communication portions. In this case, a part of the communication part can be used as an ink flow path from the main chamber to the sub chamber, and the remaining communication part can be used as an ink flow path from the sub chamber to the main chamber. This makes it possible to reliably circulate ink between the main chamber and the sub chamber.

  The plurality of communication portions have different flow path resistances, and the drive portion is configured to generate the sub chamber based on a drive signal in which rise and fall of pulses corresponding to ink drawing or discharging are asymmetric in the time axis direction. May be driven. In this case, the flow rate of the ink flowing through each communication portion can be made different between when the ink is drawn into the sub chamber and when the ink is discharged from the sub chamber, and the ink is circulated in total with the ink drawing and discharging. be able to.

  The drive unit may control the amount of ink ejected from the main chamber by driving the main chamber and the sub chamber when ink is ejected from the main chamber. In this case, since it is possible to obtain the density of one pixel without increasing the drive voltage or increasing the number of ejections, the image quality and the durability of the head can be improved.

  The drive unit may drive the main chamber and the sub chamber based on drive signals having the same phase or opposite phases. In this case, the amount of ejected ink (size of ejected ink droplets) is different between when the main chamber and the sub chamber are driven based on the drive signal having the same phase and when the drive is performed based on the drive signal having the opposite phase. Can be different.

  The inkjet head may further include a drive circuit that controls the drive signal of the sub chamber in accordance with an input signal indicating a use state of the head and supplies the drive signal to the drive unit. In this case, since the pressure in the main chamber can be made constant regardless of the use state of the head, the amount of ink ejected, the ejection speed, and the ejection cycle are stabilized during the use of the head, and the image quality is improved.

  The input signal may be a signal indicating any one of the remaining ink amount in the main chamber, the direction of the head, and the movement acceleration when ejecting ink while moving the head in one direction. In this case, the pressure in the main chamber can be made constant regardless of the remaining ink amount, the head orientation, and the movement acceleration.

  It is desirable that the flow path resistance of the communication portion is greater than or equal to the flow path resistance of the ink supply port and the nozzle hole. In this case, the main chamber and the sub chamber can be substantially separated to reliably prevent the drive frequency of the main chamber from being lowered.

  A plurality of the main chambers may be formed in the substrate, and the sub chamber may be formed in common with the plurality of main chambers in the substrate. In this case, since the volume of the sub chamber increases compared to the case where the sub chamber is formed corresponding to each main chamber, bubbles and foreign matters removed from the main chamber by the circulation of ink are diffused in the common sub chamber. , Their removal is facilitated.

  The drive unit may include a first piezoelectric element that drives the main chamber and a second piezoelectric element that drives the sub chamber. Since the main chamber is driven by the first piezoelectric element and the sub chamber is driven by the second piezoelectric element, a configuration in which the main chamber and the sub chamber are driven independently can be reliably realized.

  An ink jet printer according to another aspect of the present invention includes the above-described ink jet head, and ejects ink from the ink jet head toward a recording medium. With the configuration including the inkjet head, it is possible to realize a small, low-cost and high-performance inkjet printer.

  An ink jet head manufacturing method according to still another aspect of the present invention includes a main chamber communicating with an ink supply port, and an outside of an ink flow path from the ink supply port to the nozzle hole through the main chamber. Forming a sub-chamber driven independently of the main chamber, and a communication portion communicating the main chamber and the sub-chamber on the first substrate, and a second having the nozzle hole. Bonding the substrate to the first substrate so that the nozzle hole and the main chamber communicate with each other.

  According to the above manufacturing method, the first chamber is formed with the main chamber, the subchamber, and the communication portion that communicates these. The main chamber communicates with the ink supply port and the nozzle hole of the second substrate. In the first substrate, the sub chamber is located outside the ink flow path from the ink supply port to the nozzle hole through the main chamber and is driven independently of the main chamber. Depending on how the chamber is driven, it is possible to circulate ink and control the amount of ink ejected. Thereby, the effect similar to the effect by the structure of the above-mentioned inkjet head can be acquired.

  It is desirable that the main chamber and the sub chamber are simultaneously formed on the first substrate. In this case, since the number of processes is reduced as compared with the case where the main chamber and the sub chamber are sequentially formed, the manufacturing cost can be reduced, and the main chamber and the sub chamber can be formed with high positional accuracy.

  According to the present invention, it is possible to remove bubbles and foreign matters, suppress pressure fluctuations, and control the injection amount with a small, low-cost and simple configuration, and to suppress a decrease in driving frequency and improve durability. Can do.

1 is an explanatory diagram illustrating a schematic configuration of an inkjet printer according to an embodiment of the present invention. FIG. FIG. 2 is a plan view showing a schematic configuration of one channel of an inkjet head included in the inkjet printer, and a cross-sectional view taken along line A-A ′ in the plan view. It is explanatory drawing which shows the flow of the ink in the head at the time of the ink ejection in the said inkjet head, and the drive waveform of a 1st piezoelectric element and a 2nd piezoelectric element. It is explanatory drawing which shows the flow of the ink in the head at the time of the ink circulation in the said inkjet head, and the drive waveform of a said 1st piezoelectric element and a said 2nd piezoelectric element. It is a flowchart which shows the flow of operation | movement including the ink circulation process in the said inkjet head. FIG. 4 is an explanatory diagram showing the flow of ink in the head when ejecting large droplets of ink in the inkjet head, and the driving waveforms of the first piezoelectric element and the second piezoelectric element. FIG. 4 is an explanatory diagram showing the flow of ink in the head when ejecting small droplets of ink in the inkjet head, and the driving waveforms of the first piezoelectric element and the second piezoelectric element. In the ink jet head, it is a flowchart showing a flow of operation when driving a sub chamber according to a use state. It is a top view which shows the other structure of the said inkjet head. FIG. 3 is a cross-sectional view showing a manufacturing process of the inkjet head of FIG. 2. It is a top view which shows the general | schematic structure of the conventional inkjet head, and an a-a 'arrow sectional drawing in the top view. FIG. 2 is a plan view of one channel of the inkjet head and a cross-sectional view taken along the line b-b ′ in the plan view.

  An embodiment of the present invention will be described below with reference to the drawings.

[Configuration of inkjet printer]
FIG. 1 is an explanatory diagram illustrating a schematic configuration of an inkjet printer 1 according to the present embodiment. The ink jet printer 1 is a so-called line head type ink jet recording apparatus in which an ink jet head 21 is provided in a line shape in the width direction of a recording medium in the ink jet head unit 2.

  The ink jet printer 1 includes an ink jet head unit 2, a feed roll 3, a take-up roll 4, two back rolls 5 and 5, an intermediate tank 6, a liquid feed pump 7, a storage tank 8, and a fixing tank. And a mechanism 9.

  The ink jet head unit 2 ejects ink from the ink jet head 21 toward the recording medium P to perform image formation (drawing) based on image data, and is disposed in the vicinity of one back roll 5. The configuration of the inkjet head 21 will be described later.

  The feed roll 3, the take-up roll 4 and the back rolls 5 are members each having a cylindrical shape that can rotate about its axis. The feeding roll 3 is a roll that feeds the long recording medium P wound around the circumferential surface toward the position facing the inkjet head unit 2. The feeding roll 3 is rotated by driving means (not shown) such as a motor, thereby feeding the recording medium P in the X direction in FIG.

  The take-up roll 4 is taken out from the take-out roll 3 and takes up the recording medium P on which the ink is ejected by the ink jet head unit 2 around the circumferential surface.

  Each back roll 5 is disposed between the feed roll 3 and the take-up roll 4. One back roll 5 located on the upstream side in the conveyance direction of the recording medium P is opposed to the inkjet head unit 2 while winding the recording medium P fed by the feeding roll 3 around and supporting the recording medium P. Transport toward The other back roll 5 conveys the recording medium P from a position facing the inkjet head unit 2 toward the take-up roll 4 while being wound around and supported by a part of the peripheral surface.

  The intermediate tank 6 temporarily stores the ink supplied from the storage tank 8. The intermediate tank 6 is connected to the ink tube 10, adjusts the back pressure of the ink in each inkjet head 21, and supplies the ink to each inkjet head 21.

  The liquid feed pump 7 supplies the ink stored in the storage tank 8 to the intermediate tank 6 and is disposed in the middle of the supply pipe 11. The ink stored in the storage tank 8 is pumped up by the liquid feed pump 7 and supplied to the intermediate tank 6 through the supply pipe 11.

  The fixing mechanism 9 fixes the ink ejected to the recording medium P by the inkjet head unit 2 on the recording medium P. The fixing mechanism 9 includes a heater for heating and fixing the ejected ink on the recording medium P, a UV lamp for curing the ink by irradiating the ejected ink with UV (ultraviolet light), and the like. Yes.

  In the above configuration, the recording medium P fed from the feeding roll 3 is transported to the position facing the inkjet head unit 2 by the back roll 5, and ink is ejected from the inkjet head unit 2 to the recording medium P. Thereafter, the ink ejected onto the recording medium P is fixed by the fixing mechanism 9, and the recording medium P after ink fixing is taken up by the take-up roll 4. As described above, in the line head type inkjet printer 1, ink is ejected while the recording medium P is conveyed while the inkjet head unit 2 is stationary, and an image is formed on the recording medium P.

  The ink jet printer 1 may be configured to form an image on a recording medium by a serial head method. The serial head method is a method of forming an image by ejecting ink by moving an inkjet head in a direction orthogonal to the transport direction while transporting a recording medium.

[Configuration of inkjet head]
Next, the configuration of the inkjet head 21 will be described. FIG. 2 is a plan view showing a schematic configuration of one channel (ink ejection portion) 21a of the inkjet head 21 and a sectional view taken along the line AA ′ in the plan view. The ink jet head 21 is roughly composed of a body 31 and a nozzle substrate 32. The nozzle substrate 32 has a nozzle hole 32a for controlling the amount of ink droplets to be ejected. The size of the nozzle hole 32a is, for example, 50 μm in diameter and 50 μm in depth (same as the thickness of the nozzle substrate 32).

The body 31 is configured by disposing a drive unit 44 on a body substrate 41 made of, for example, a silicon substrate having a thickness of 500 μm with a diaphragm 42 and an insulating film 43 interposed therebetween. The nozzle substrate 32 is bonded to the body substrate 41 on the side opposite to the side where the drive unit 44 is formed. The diaphragm 42 is a driven film that vibrates when driven by the drive unit 44, and is made of, for example, a silicon substrate that is thinner than the body substrate 41. The insulating film 43 is made of a thermal oxide film such as silicon oxide (SiO ₂ ), and is provided for the purpose of protection and insulation.

  In the body substrate 41, a main chamber 41a, a sub chamber 41b, and a communication portion 41c are formed. The diaphragm 42 constitutes the upper wall of the main chamber 41a, the sub chamber 41b, and the communication portion 41c, that is, the wall on the side facing the nozzle substrate 32.

  The main chamber 41a is in communication with the ink supply port 45 and the nozzle hole 32a, and is driven by a drive unit 44 (first piezoelectric element 44a described later), so that the ink supplied from the ink supply port 45 is a nozzle. Injection from the hole 32a. The ink supply port 45 is formed so as to penetrate through the vibration plate 42 and the insulating film 43, and the end opposite to the main chamber 41a is connected to the ink tube 10 (see FIG. 1). . The size of the main chamber 41a is, for example, 500 μm in diameter and 500 μm in depth, and the size of the ink supply port 45 is, for example, 50 μm in diameter and 50 μm in depth. The size of the main chamber 41a is shown for the remaining cylindrical space excluding the space below the ink supply port 45.

  The sub chamber 41b is a space located alongside the main chamber 41a on the outside of the ink flow path from the ink supply port 45 to the nozzle hole 32a via the main chamber 41a. The piezoelectric element 44b) is driven independently of the main chamber 41b. That is, the sub chamber 41b is not positioned in the ink flow path (in series with the main chamber 41a), but is positioned in parallel with the main chamber 41a with respect to the ink flow path. The sub chamber 41b is formed in, for example, a cylindrical shape, and the size thereof is, for example, a diameter of 300 μm and a depth of 500 μm.

The communication portion 41c is a passage that communicates the main chamber 41a and the sub chamber 41b. In this embodiment, the main chamber 41a and the sub chamber 41b communicate with each other through the two communication portions 41c ₁ and 41c ₂ arranged in parallel. ing. The size of the communicating portion 41c _1, for example width 30 [mu] m, depth 500 [mu] m, a length of 50 [mu] m. The size of the communicating portion 41c _2, for example width 20 [mu] m, depth 500 [mu] m, a length of 50 [mu] m. The width of the communication portions 41c ₁ and 41c ₂ refers to the length in the direction perpendicular to the communication direction connecting the main chamber 41a and the sub chamber 41b in the plan view of FIG. 2, and the communication portions 41c ₁ and 41c. The length of ₂ refers to the length in the communication direction. The main chamber 41a and the sub chamber 41b may communicate with each other via three or more communication portions 41c.

  The drive unit 44 independently drives the main chamber 41a and the sub chamber 41b, and in this embodiment, the first piezoelectric element 44a that drives the main chamber 41a and the second that drives the sub chamber 41b. And the piezoelectric element 44b. Driving the main chamber 41a means applying a positive pressure or negative pressure in the main chamber 41a, and driving the sub chamber 41b means applying a positive pressure or negative pressure in the sub chamber 41b.

  The first piezoelectric element 44a is configured by laminating a lower electrode 51a, a piezoelectric thin film 52a, and an upper electrode 53a in this order from the body substrate 41 side. The lower electrode 51a and the upper electrode 53a are connected to the drive circuit 46, and the first piezoelectric element 44a is driven based on the drive voltage (drive signal) supplied from the drive circuit 46.

  The second piezoelectric element 44b is configured by laminating a lower electrode 51b, a piezoelectric thin film 52b, and an upper electrode 53b in this order from the body substrate 41 side. The lower electrode 51b and the upper electrode 53b are connected to the drive circuit 46, and the second piezoelectric element 44b is driven based on a drive signal supplied from the drive circuit 46. The drive circuit 46 may be provided individually corresponding to each of the first piezoelectric element 44a and the second piezoelectric element 44b.

  The vibration plate 42, the insulating film 43, and the drive unit 44 (particularly the first piezoelectric element 44 a) constitute an actuator of the inkjet head 21.

[Operation when ink is ejected]
FIG. 3 shows the flow of ink in the head during ink ejection and the drive waveforms of the first piezoelectric element 44a and the second piezoelectric element 44b. When the rectangular drive signal shown in the figure is applied from the drive circuit 46 to the first piezoelectric element 44a, the vibration in the vertical direction of the vibration plate 42 due to the expansion and contraction of the first piezoelectric element 44a is applied to the ink in the main chamber 41a. Pressure is applied, and the ink is ejected to the outside from the nozzle hole 32a. In addition, since the drive voltage in the drive signal of the 2nd piezoelectric element 44b shown in FIG. 3 remains with the reference voltage (voltage V3), the subchamber 41b is not driven substantially.

  In the drive signal of the first piezoelectric element 44a, since the acceleration / deceleration time, that is, the rise and fall times of the pulses are short, the ink in the sub chamber 41b communicated by the communication portion 41c hardly moves. Therefore, ink can be ejected at substantially the same droplet amount, speed, and frequency as when there is no sub chamber 4b. That is, when the ink is ejected, the ink in the main chamber 41a can be ejected from the nozzle hole 32a by driving the main chamber 41a by the first piezoelectric element 44a as described above.

  Incidentally, as an example of the drive signal of the first piezoelectric element 44a, applied voltage: 20V (V1 = 0V, V2 = 20V), pulse width: 10 μsec (t2-t1 = 10 μsec), frequency: 10 kHz (t3-t1) = 100 μsec).

[About channel resistance]
In the present embodiment, the sizes of the _two communication portions 41c ₁ and 41c ₂ are set as described above, and the widths are different from each other. Therefore, the flow path resistance of the communicating portion _41c 1 · 41c ₂ are different from each other.

Here, the flow path resistance refers to the difficulty of the substance (ink) flowing through the communication portions 41c ₁ and 41c ₂ . That is, as the widths of the communication portions 41c ₁ and 41c ₂ become smaller or the length of the flow path becomes longer, the ink becomes harder to flow, so the flow path resistance becomes larger. The flow path resistances of the communication portions 41c ₁ and 41c ₂ change in accordance with the pressure reduction rate (volume change rate) in the main chamber 41a or the sub chamber 41b by the drive unit 44, respectively. The larger the speed of (the larger the volume change rate), the greater the flow path resistance. In the present embodiment, the rate of change in flow path resistance (change rate of flow path resistance) with respect to the change in pressure reduction or pressurization speed is different between the communication portions 41c ₁ and 41c ₂ , and the communication portion having a larger width. towards the 41c ₁ is width than is smaller than the communicating portion 41c _2, (change in flow path resistance is small with respect to change in speed of the vacuum or pressure) the rate of change of flow path resistance is small.

Therefore, by devising a driving signal of the second piezoelectric element 44b to drive the sub-chamber 41b (drive waveform) between the main chamber 41a and the auxiliary chamber 41b, via the communication unit _41c 1 · 41c ₂ Ink can be circulated. Hereinafter, the operation during ink circulation will be described.

[Operation during ink circulation]
FIG. 4 shows the flow of ink in the head during ink circulation and the driving waveforms of the first piezoelectric element 44a and the second piezoelectric element 44b. The ink is circulated by applying a triangular wave-shaped drive signal shown in the figure to the second piezoelectric element 44b by the drive circuit 46 when the ink is not ejected (for example, before and after ink ejection). The second piezoelectric element 44b drives the sub chamber 41b based on the drive signal. Note that the drive voltage in the drive signal of the first piezoelectric element 44a shown in FIG. 4 remains the reference voltage (voltage V1), so the main chamber 41a is not substantially driven.

  Here, the drive signal (applied voltage, applied time, frequency) of the second piezoelectric element 44b varies depending on the physical properties of the ink and the performance of the actuator, but is set to a waveform that does not eject ink from the main chamber 41a. An example of the drive signal of the second piezoelectric element 44b is as follows. Applied voltage: 10 V (V3 = 0 V, V4 = 10 V), pulse width: 100 μsec (t2−t1 = 100 μsec), frequency: 1 kHz (t3− t1 = 1000 μsec).

By increasing the voltage applied to the second piezoelectric element 44b from V3 to V4 from time t1 to time t2, the diaphragm 42 of the sub chamber 41b is curved so as to protrude upward, and negative pressure is generated in the sub chamber 41b. Therefore, the ink in the main chamber 41a is drawn into the sub chamber 41b through the communication portion 41c. At this time, since the deformation speed of the vibration plate 42 is slow, the pressure change is small, and the change in flow path resistance of the communication portions 41c ₁ and 41c ₂ is small. Therefore, both the ink from the communicating portion _41c 1 · 41c ₂ of is drawn into the auxiliary chamber 41b (flow rate ratio of the communicating portion _41c 1 · 41c ₂ in this case is for example 3: 2).

And the diaphragm 42 of the subchamber 41b returns to the original position by lowering the voltage applied to the second piezoelectric element 44b to V3 at the time t2. At this time, the deformation speed of the vibration plate 42 is fast, the flow path resistance of the communicating portion _41c 1 · 41c ₂ is changed, between the communicating portion _41c 1 · 41c _2, the difference in the flow rate increases due to pressure changes. As a result, from the auxiliary chamber 41b, width via a relatively large communication portion 41c _1, more ink is ejected to the main chamber 41a (the flow rate ratio of the communicating portion _41c 1 · 41c ₂ in this case is For example, 4: 1).

Thus, the time of pull-in of the ink into the sub-chamber 41b, at a time of ejection of ink from the auxiliary chamber 41b, to change the flow rate of the ink flowing through the communicating portion 41c 1 _· 41c ₂ is, one ink pull the when considered in total combined discharge and the ink passes through the communicating portion 41c ₂ flows from the main chamber 41a to the sub-chamber 41b, flows through the communicating portion 41c ₁ from sub-chamber 41b to the main chamber 41a Can be considered. Therefore, by repeating this operation periodically, it is possible to circulate ink between the main chamber 41a and the sub chamber 41b, thereby removing bubbles and foreign matters in the main chamber 41a.

  The above-described ink circulation operation can be performed, for example, at the following timing. FIG. 5 is a flowchart showing an operation flow including an ink circulation process in the inkjet head 21 of the present embodiment.

  First, when the power of the inkjet printer 1 is turned on (S1), the above-described ink circulation operation is performed (S2). Subsequently, the number N of prints is set to N = 1 (S3), and the above-described ink ejection operation is performed. (S4). Thereafter, N = N + 1 is set (S5), and a control unit (not shown) determines whether printing has been completed up to the last page (S6). If the printing is finished in S6, the ink circulation operation is performed again (S7), and the series of operations is finished.

  On the other hand, if printing has not ended in S6, it is determined whether n is a natural number, A is a predetermined number (for example, 50 sheets), and the number N of printed sheets is N = n · A ( S8). If N = n · A is not satisfied in S8 (if the number of printed sheets has not reached the predetermined number), it is determined that there is no need to perform ink circulation, and the operations after S4 are repeated. On the other hand, when N = n · A in S8 (when the number of printed sheets reaches a predetermined number), it is determined that it is necessary to remove bubbles and foreign matters by printing a predetermined number of sheets (S9). Thereafter, the operations after S4 are repeated.

  The print image and the vicinity of the nozzles are observed with a camera, and ink circulation may be performed if an ejection abnormality has occurred.

  As described above, the drive unit 44 (particularly the second piezoelectric element 44b) drives the sub chamber 41b when ink is not ejected to circulate the ink, thereby removing bubbles and foreign matters in the main chamber 41a. Can do. Thereby, it is possible to reduce ink ejection defects caused by bubbles and foreign matters.

  Also, pigment is dispersed as a color material in the ink. As time elapses, the pigment settles, and the physical properties such as viscosity and specific gravity of the ink in the lower layer change. When the physical properties of the ink change, the ink ejection amount and ejection speed change, and the image quality deteriorates. However, since the ink pigment can be diffused by the above-described ink circulation, it is possible to avoid a decrease in print image quality due to a change in ink physical properties.

Further, the main chamber 41a and the auxiliary chamber 41b, because in communication via a plurality of communication portions _41c 1 · 41c _2, as described above in one of the communicating portion 41c _2, the auxiliary chamber 41b from the main chamber 41a toward used as a flow path of the ink, the rest of the communicating portion 41c _1, can be used as an ink flow path extending from the auxiliary chamber 41b to the main chamber 41a. Thereby, it is possible to reliably circulate ink between the main chamber 41a and the sub chamber 41b.

The plurality of communication portions 41c ₁ and 41c ₂ have different flow path resistances, and the second piezoelectric element 44b drives the sub chamber 41b based on the drive signal shown in FIG. the flow rate of the ink flowing through the ₁ · 41c _2, can be different in the time of pull-in of the ink into the sub-chamber 41b, the time of ejection of the ink from the auxiliary chamber 41b. As a result, the ink can be circulated in a total of ink drawing and discharging.

The driving signal of the second piezoelectric element 44b when the ink circulation is not limited to a triangular waveform of the drive signal of FIG. 4, in the discharge and retraction of the ink, the flow of the communication portion 41c 1 _· 41c ₂ Any signal that changes the ink flow rate due to a change in path resistance may be used. In other words, the drive signal may be a signal in which the rise and fall of the pulse corresponding to ink drawing or ejection are asymmetric in the time axis direction, such as a triangular wave in which both the rise and fall of the pulse are inclined. A trapezoidal wave may be used.

  In the above, only the sub chamber 41b is driven during ink circulation, but the main chamber 41a may be further driven. In this case, it is necessary to control the drive signal of the main chamber 41a so that the ink is not ejected, but the amount of circulating ink increases by driving the main chamber 41a in addition to the sub chamber 41b. Therefore, it is possible to promote the removal of bubbles and foreign matters in the main chamber 41a.

In the above description, the two communication portions 41c ₁ and 41c ₂ are provided as the communication portion 41c so as to circulate the ink. However, in realizing the ink circulation, the number of the communication portions 41c is three or more. It may be one or one. Even when there is only one communication portion 41c, for example, it is possible to circulate ink by changing the ink moving direction between the upper position and the lower position of the same communication portion 41c.

[Control of ink ejection amount]
The drive unit 44 may drive both the main chamber 41a and the sub chamber 41b when ink is ejected from the main chamber 41a. For example, the pressure in the main chamber 41a can be increased or decreased by driving the sub chamber 41b at the same timing as the ink ejection from the main chamber 41a, thereby controlling the amount of ink ejected from the main chamber 41a. it can.

  FIG. 6 shows the flow of ink in the head when ejecting large droplets of ink and the driving waveforms of the first piezoelectric element 44a and the second piezoelectric element 44b. As shown in the figure, when the second piezoelectric element 44b drives the sub chamber 41b based on a drive signal having the same phase as the drive signal of the first piezoelectric element 44a, the pressure in the main chamber 41a increases. Ink ejection amount can be increased (large droplet ink can be ejected).

  FIG. 7 shows the flow of ink in the head when ejecting small droplets of ink and the driving waveforms of the first piezoelectric element 44a and the second piezoelectric element 44b. As shown in the figure, when the second piezoelectric element 44b drives the sub chamber 41b based on a drive signal having a phase opposite to that of the first piezoelectric element 44a, the pressure in the main chamber 41a decreases. The amount of ink ejected can be reduced (small droplets of ink can be ejected).

  An example of the driving waveform of the sub chamber 41b during the injection amount control is as follows: applied voltage: 10 V (V3 = 0 V, V4 = 10 V), pulse width: 10 μsec (t2−t1 = 10 μsec), frequency: 10 kHz (t3− t1 = 100 μsec).

  Thus, the drive unit 44 (the first piezoelectric element 44a and the second piezoelectric element 44b) drives both the main chamber 41a and the sub chamber 41b to increase the drive voltage or increase the number of injections. The amount of ink ejection can be controlled without causing it to occur. Thereby, the durability of the head can be improved. Further, by controlling the ink ejection amount, the density of one pixel can be obtained, so that the image quality of the printed image can be improved.

  In particular, the drive unit 44 controls the ink ejection amount (droplet size) in two stages by driving the main chamber 41a and the sub chamber 41b based on the drive signals having the same or opposite phases. be able to. Therefore, including the driving of FIG. 3 in which the sub chamber 41b is not driven at all, the ink ejection amount can be adjusted in a total of three stages.

[Suppression of pressure fluctuation]
The drive circuit 46 may control the drive signal (for example, voltage or phase) of the sub chamber 41b according to the input signal indicating the use state of the inkjet head 21, and supply the drive signal to the second piezoelectric element 44b. Here, the input signal includes the remaining amount of ink in the main chamber 41a, the head direction (head mounting angle in the line head system), and the movement acceleration (serial) when ejecting ink while moving the head in one direction. A signal indicating the movement acceleration in the head system) can be considered. The remaining amount of ink, the head mounting angle, and the acceleration during movement of the head can be detected by a sensor (not shown), and an output signal from this sensor becomes an input signal to the drive circuit 46.

  For example, when the pressure of the ink supply port 45 decreases due to a low ink remaining amount, a line head method in which the ink ejection direction is inclined from the vertical direction, a head acceleration or deceleration in the serial head method, etc. The second piezoelectric element 44b increases the pressure in the main chamber 41a by driving the sub chamber 41b with a drive signal having the same phase as the drive signal of the first piezoelectric element 44a. On the contrary, when the pressure of the ink supply port 45 rises due to a large amount of remaining ink, the second piezoelectric element 44b is driven by the sub chamber 41b with a drive signal having a phase opposite to that of the first piezoelectric element 44a. To reduce the pressure in the main chamber 41a. By driving the sub chamber 41b, the pressure in the main chamber 41a can be made almost constant regardless of the use state of the head.

  FIG. 8 is a flowchart showing an operation flow when the sub chamber 41b is driven in accordance with the use state in the inkjet head 21 of the present embodiment. First, when the power supply of the ink jet printer 1 is turned on (S11), information such as the remaining ink amount, the head orientation, and the acceleration during the movement of the head is detected by a sensor (not shown), and these detection signals are driven in real time. 46 (S12). Since the head direction (mounting angle) is constant and hardly changes during use, once it is detected, the same detection signal is output to the drive circuit 46 thereafter. Further, the remaining amount of ink and the acceleration during movement of the head are detected by a sensor every time a pixel is drawn, and the detection signal is output to the drive circuit 46.

  Next, the drive circuit 46 determines the drive waveform (the voltage and phase of the drive signal of the second piezoelectric element 44b) of the sub chamber 41b based on the received detection signal (for example, the sign of the signal, magnitude). S13). Then, the drive circuit 46 supplies a desired drive signal corresponding to the image signal to the first piezoelectric element 44a to drive the main chamber 41a, and the drive signal determined in S13 to the second piezoelectric element 44b. Then, the sub chamber 41b is driven to eject ink from the main chamber 41a (S14). Thereafter, the process ends when the printing ends (Yes in S15), but if the printing does not end (No in S15), the process returns to S12 and the subsequent operations are repeated.

  As described above, the drive circuit 46 controls the drive signal of the sub chamber 41b according to the input signal indicating the usage state of the head and supplies it to the second piezoelectric element 44b to drive the second piezoelectric element 44b. Therefore, the pressure in the main chamber 41a can be made constant regardless of the usage state of the head. As a result, the ink ejection amount, ejection speed, and ejection cycle can be stabilized during use of the head, and the image quality can be improved.

  In particular, since the input signal is a signal indicating any of the remaining ink amount in the main chamber 41a, the head orientation, and the head moving acceleration, the pressure in the main chamber 41a is kept constant regardless of these states. can do.

[Summary]
As described above, according to the ink jet head 21 of the present embodiment, the sub-chamber 41b that is driven independently of the main chamber 41a is formed on the body substrate 41 on which the main chamber 41a is formed. Ink circulation, ink ejection amount control, and pressure fluctuation in the main chamber 41a can be suppressed. In particular, since the sub chamber 41b is located outside the ink flow path flowing through the main chamber 41a in the body substrate 41, bubbles or foreign matter generated in the main chamber 41a due to the ink circulation described above, or the main chamber 41a. Inflowing bubbles and foreign matters can be effectively removed. Further, by independently driving the main chamber 41a and the sub chamber 41b, the ink ejection amount can be controlled without increasing the driving voltage or increasing the number of ejections, so that the durability of the head can be improved.

  Moreover, since the main chamber 41a and the sub chamber 41b are divided by the communication part 41c, it can suppress that the volume of the main chamber 41a increases substantially by providing the sub chamber 41b. Thereby, it can suppress that the drive frequency of the main chamber 41a falls, and high-speed drive can be implement | achieved.

  Here, due to the sizes of the main chamber 41a, the sub chamber 41b, the communication portion 41c, the ink supply port 45, and the nozzle hole 32a in one channel 21a of the ink jet head 21, the flow path resistance of the communication portion 41c is the ink supply port. 45 and the flow path resistance of the nozzle hole 32a. By doing so, it is possible to reliably separate the main chamber 41a and the sub chamber 41b by the communication portion 41c, and the drive frequency of the main chamber 41a is reduced by providing the sub chamber 41b. It can be surely suppressed.

  Moreover, since the main chamber 41a, the sub chamber 41b, and the communication part 41c are formed in the same body substrate 41, the circulation of the ink within the same substrate is realizable. Thereby, it is not necessary to add an external mechanism necessary for ink circulation such as a pump. In addition, pressure fluctuation can be suppressed without using an external mechanism. Thereby, the above-described effects can be obtained with a small size, low cost, and simple configuration. By using such an inkjet head 21, it is possible to realize a high-performance inkjet printer 1 that is small in size and low in cost.

  In addition, since the sub chamber 41b is provided in the vicinity of the main chamber 41a in the body substrate 41 in the vicinity thereof, a large pressing force is not required during ink circulation or the like, and failure of the head or the flow path is unlikely to occur. It will be a thing. Moreover, since the sub chamber 41b is located in the vicinity of the main chamber 41a, there is no pressure loss or response time delay, and the control accuracy is improved.

  In the present embodiment, the drive unit 44 can drive only the main chamber 41a, only the sub chamber 41b, or both the main chamber 41a and the sub chamber 41b. Circulation, ink ejection amount control, and the like can be reliably performed. In particular, the drive unit 44 includes a first piezoelectric element 44a that drives the main chamber 41a and a second piezoelectric element 44b that drives the sub chamber 41b, and driving means for the main chamber 41a and the sub chamber 41b. Therefore, the main chamber 41a and the sub chamber 41b can be reliably driven independently.

[Other configurations of inkjet head]
FIG. 9 is a plan view showing another configuration of the inkjet head 21. As shown in the figure, a plurality of main chambers 41a are formed in the body substrate 41 (see FIG. 2), and a sub chamber 41b is formed in the body substrate 41 in common with the plurality of main chambers 41a. Also good. That is, one sub chamber 41b may be configured to communicate with the plurality of main chambers 41a via the communication portion 41c.

  In this case, the volume of the sub chamber 41b increases compared to the case where the sub chamber 41b is formed corresponding to each main chamber 41a. Then, bubbles and foreign matter moved from the main chamber 41a to the sub chamber 41b by the circulation of the ink are diffused in the sub chamber 41b having a large volume. For this reason, it becomes difficult for bubbles and foreign substances to return from the sub chamber 41b to the main chamber 41a by circulation, and the removal of the bubbles and foreign substances in the main chamber 41a as a whole is promoted.

[Inkjet head manufacturing method]
Next, a method for manufacturing the ink jet head of this embodiment will be described. FIG. 10 is a cross-sectional view showing a manufacturing process of the ink jet head 92 corresponding to the ink jet head 21 of FIG. Note that the following manufacturing method can also be applied to the inkjet head 21 of FIG.

  First, the substrate 61 is prepared. As the substrate 61, crystalline silicon (Si) often used in MEMS (Micro Electro Mechanical Systems) can be used. Here, two Si substrates 61a (first substrate) are interposed via an oxide film 61b. -The SOI structure with 61c bonded is used. The Si substrates 61a and 61c correspond to the body substrate 41 and the diaphragm 42 in FIG. The thickness of the substrate 61 is determined by a standard or the like. In the case of a 6-inch diameter, the thickness is about 600 μm.

Next, the substrate 61 is put into a heating furnace and held at about 1500 ° C. for a predetermined time, and thermal oxide films 62a and 62b made of SiO ₂ are formed on the surfaces of the Si substrates 61a and 61c, respectively. The thermal oxide film 62b on the surface of the Si substrate 61c corresponds to the insulating film 43 in FIG. Thereafter, titanium and platinum layers are sequentially formed on the thermal oxide film 62b by sputtering to form the lower electrode 63. The lower electrode 63 corresponds to an electrode having the lower electrodes 51a and 51b in FIG. 2 in common. The lower electrode 63 may be patterned so as to correspond to each of the lower electrodes 51a and 51b.

  Subsequently, the substrate 61 is reheated to about 600 ° C., and a lead zirconate titanate (PZT) layer 64a as a piezoelectric body is formed by sputtering. Then, a photosensitive resin 71 is applied on the layer 64a by a spin coating method, and exposure and etching are performed through a mask. Thereby, unnecessary portions of the photosensitive resin 71 are removed, and the shape of the piezoelectric layer 64 to be formed is transferred. Thereafter, unnecessary portions of the layer 64a are removed by reactive ion etching using the patterned photosensitive resin 71 as a mask. Thereby, on the lower electrode 63, the piezoelectric layer 64 corresponding to the piezoelectric thin film 52a of FIG. 2 and the piezoelectric layer 64 corresponding to the piezoelectric thin film 52b are simultaneously formed.

  Next, a titanium layer and a platinum layer are sequentially formed by sputtering on the lower electrode 63 so as to cover the piezoelectric layer 64, thereby forming a layer 65a. Subsequently, a photosensitive resin 72 is applied onto the layer 65a by a spin coating method, and exposure and etching are performed through a mask. Thereby, unnecessary portions of the photosensitive resin 72 are removed, and the shape of the upper electrode 65 to be formed is transferred. Thereafter, unnecessary portions of the layer 65a are removed using a reactive ion etching method using the photosensitive resin 72 as a mask. Thereby, the upper electrode 65 corresponding to the upper electrode 53a of FIG. 2 and the upper electrode 65 corresponding to the upper electrode 53b are formed on the piezoelectric layer 64. And the 1st piezoelectric element 66a which drives the below-mentioned main chamber 81, and the 2nd piezoelectric element 66b which drives the subchamber 82 are formed. The first piezoelectric element 66a and the second piezoelectric element 66b constitute a drive unit corresponding to the first piezoelectric element 44a and the second piezoelectric element 44b in FIG. 2, respectively.

  Next, a photosensitive resin 73 is applied to the back surface of the substrate 61 by a spin coat method, and exposure and etching are performed through a mask, thereby removing unnecessary portions of the photosensitive resin 73 and forming a main chamber 81 to be formed. The shape of the sub chamber 82 and the communication portion is transferred. Then, using the photosensitive resin 73 as a mask, the substrate 61 is removed using a reactive ion etching method to form the main chamber 81, the sub chamber 82, and the communication portion. The main chamber 81, the sub chamber 82, and the communication portion respectively correspond to the main chamber 41a, the sub chamber 41b, and the communication portion 41c of FIG.

  Next, the lower electrode 63, the thermal oxide film 62b, and the Si substrate 61c above the end of the main chamber 81 are etched to form an ink supply port 67 that passes through these and communicates with the main chamber 81. Thereafter, the thermal oxide film 62a on the back side of the substrate 61 is removed, and the substrate 61 and the nozzle plate 91 (second substrate) are bonded together by anodic bonding via an adhesive or intermediate glass. At this time, the main chamber 81 of the substrate 61 and the nozzle hole 91a of the nozzle plate 91 are bonded together so as to communicate with each other. Thereby, the inkjet head 92 is completed. The ink supply port 67, the nozzle plate 91, and the nozzle hole 91a correspond to the ink supply port 45, the nozzle substrate 32, and the nozzle hole 32a of FIG.

  By the above manufacturing method, the main chamber 81, the sub chamber 82, and the communication portion are formed on the same substrate 61. In the substrate 61, the sub chamber 82 is located outside the ink flow path from the ink supply port 66 to the nozzle hole 91a via the main chamber 81, and is driven independently of the main chamber 81. It is possible to control the circulation of ink and the amount of ink ejection in the same substrate as described above. Thereby, the effect similar to the effect by the structure of the above-mentioned inkjet head 21 can be acquired.

  Further, by simultaneously forming the main chamber 81 and the sub chamber 82 on the substrate 61 (particularly the Si substrate 61a), the number of processes is reduced as compared with the case where these are sequentially formed in separate processes, thereby reducing the manufacturing cost. In addition, the main chamber 81 and the sub chamber 82 can be formed with high positional accuracy.

  In addition, since the piezoelectric layer 64 corresponding to the main chamber 81 and the piezoelectric layer 64 corresponding to the sub chamber 82 are also formed at the same time, they can be formed with high positional accuracy. Similarly, since the upper electrode 65 corresponding to the main chamber 81 and the upper electrode 65 corresponding to the sub chamber 82 are formed at the same time, these can be formed with high positional accuracy.

[Others]
In the present embodiment, the flow path resistances are made different from each other by making the widths of the plurality of communication portions 41c ₁ and 41c ₂ different. For example, the formation direction of the communication portions 41c ₁ and 41c ₂ is devised to make the communication direction of or with different lengths, or to place an obstacle such as a filter in one of the communicating portion 41c _2, by arranging a movable valve, it may be made different flow resistance to each other.

  In the present embodiment, ink is circulated at least immediately before the start of printing and after all printing has been completed. In addition, even when the number of printed sheets reaches a predetermined number (after the completion of printing of a predetermined number of sheets, Although the ink is circulated (even in the non-printing section before the start of printing of the paper), the ink may be circulated in the non-printing pixel section in one sheet.

  In the present embodiment, the case of using a piezoelectric actuator has been described. However, the drive method of the present embodiment is applied even when an actuator of another system such as an electrostatic system, an electromagnetic system, or thermal deformation is used. Thus, the same effect as that of the present embodiment can be obtained.

  The ink jet head of the present invention can be used in an ink jet printer.

DESCRIPTION OF SYMBOLS 1 Inkjet printer 21 Inkjet head 32a Nozzle hole 41 Body substrate 41a Main chamber 41b Sub chamber 41c Communication part 41c ₁ communication part 41c ₂ communication part 44 Drive part 44a 1st piezoelectric element 44b 2nd piezoelectric element 45 Ink supply port 46 Drive Circuit 61a Si substrate (first substrate)
67 Ink supply port 81 Main chamber 82 Sub chamber 91 Nozzle plate (second substrate)
91a Nozzle hole 92 Inkjet head

Claims (15)

An inkjet head comprising a substrate on which a main chamber communicating with an ink supply port and a nozzle hole is formed, and ejecting ink in the main chamber from the nozzle hole,
In the substrate on which the main chamber is formed,
A sub chamber driven independently of the main chamber;
A communication portion that connects the main chamber and the sub chamber is formed,
The inkjet head according to claim 1, wherein the sub chamber is located outside the ink flow path from the ink supply port to the nozzle hole through the main chamber in the substrate.   The inkjet head according to claim 1, further comprising a drive unit that independently drives the main chamber and the sub chamber.   The drive unit circulates ink between the main chamber and the sub chamber through the communication unit by driving the sub chamber when ink is not ejected from the main chamber. The inkjet head according to claim 2.   The ink jet head according to claim 3, wherein the main chamber and the sub chamber communicate with each other via a plurality of the communication portions. The plurality of communicating portions have different flow path resistances,
5. The drive unit according to claim 4, wherein the drive unit drives the sub chamber based on a drive signal in which rise and fall of pulses corresponding to ink drawing or discharging are asymmetric in the time axis direction. Inkjet head.   The said drive part controls the ejection amount of the ink from the said main chamber by driving the said main chamber and the said subchamber at the time of the ink ejection from the said main chamber. The ink jet head according to any one of the above.   The inkjet head according to claim 6, wherein the driving unit drives the main chamber and the sub chamber based on drive signals having the same phase or opposite phases.   The inkjet according to claim 6, further comprising a drive circuit that controls a drive signal of the sub chamber according to an input signal indicating a use state of the head and supplies the drive signal to the drive unit. head.   The input signal is a signal indicating any one of a remaining amount of ink in the main chamber, a direction of the head, and a moving acceleration when ejecting ink while moving the head in one direction. The inkjet head according to 8.   10. The ink jet head according to claim 1, wherein a flow path resistance of the communication portion is greater than or equal to a flow path resistance of the ink supply port and the nozzle hole. A plurality of the main chambers are formed on the substrate,
The inkjet head according to claim 1, wherein the sub chamber is formed in common with the plurality of main chambers in the substrate.   The inkjet head according to claim 2, wherein the driving unit includes a first piezoelectric element that drives the main chamber and a second piezoelectric element that drives the sub chamber.   An inkjet printer comprising the inkjet head according to claim 1, wherein ink is ejected from the inkjet head toward a recording medium. A main room communicating with the ink supply port;
A sub chamber located outside the ink flow path from the ink supply port to the nozzle hole through the main chamber and driven independently of the main chamber;
Forming a communication portion for communicating the main chamber and the sub chamber on the first substrate;
A method for manufacturing an ink jet head, comprising: bonding a second substrate having the nozzle hole to the first substrate so that the nozzle hole and the main chamber communicate with each other.   The method of manufacturing an ink jet head according to claim 14, wherein the main chamber and the sub chamber are simultaneously formed on the first substrate.

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