Liquid dispensing apparatus, image forming apparatus, and control method

Abstract

To provide a liquid discharge device that can stably discharge quick-drying ink, using a simple and inexpensive inkjet head and a control system, an image forming device and a control method.SOLUTION: A liquid discharge device comprises: at least one nozzle hole that discharges liquid; a plurality of pressure chambers communicating with the nozzle hole; a fluid resistance part connected to the pressure chambers; and a control part that makes the nozzle hole discharge second liquid for forming an image, after the nozzle hole discharges first liquid not for forming an image. The number of droplets of the discharged first liquid is equal to the number of droplets of amounts of liquid exceeding volumes of the pressure chamber whose cross-sectional area which is orthogonal to a flowing direction of liquid from the fluid resistance part to the nozzle hole is larger than a predetermined cross-sectional area, of the plurality of pressure chambers.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to a liquid ejection device, an image forming device, and a control method.

Background Art

[0002] In an inkjet head, a flow-through technique for circulating ink (an example of a liquid) near a nozzle hole is disclosed (see Patent Document 1). By using the flow-through technique, clogging of the nozzle hole due to drying and thickening of the ink near the nozzle hole can be suppressed, and quick-drying ink can be used with a liquid ejection head such as an inkjet head.

Summary of the Invention

Problems to be Solved by the Invention

[0003] However, since the flow-through technique complicates the configuration of the inkjet head and its control system and makes it expensive, it is difficult to use quick-drying ink with a simple and inexpensive system.

[0004] The present invention has been made in view of the above, and an object thereof is to provide a liquid ejection device, an image forming device, and a control method that can stably eject quick-drying ink using a simple and inexpensive inkjet head and control system.

Means for Solving the Problems

[0005] In order to solve the above-described problems and achieve the object, the present invention includes at least one nozzle hole that ejects a liquid, a plurality of pressure chambers that communicate with the nozzle hole, a fluid resistance portion connected to the pressure chamber, and a control unit that ejects a second liquid for image formation from the nozzle hole after ejecting a first liquid that does not perform image formation from the nozzle hole. The number of drops of the first liquid ejected is greater than the volume of the pressure chamber among the plurality of pressure chambers, in which the cross-sectional area orthogonal to the flow direction of the liquid from the fluid resistance portion to the nozzle hole is larger than a predetermined cross-sectional area. At that point of the number of drops of the liquid. [Effects of the Invention]

[0006] According to the present invention, a simple and inexpensive inkjet head and control system can be used to stably eject quick-drying ink, which is a desirable effect. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a diagram illustrating an example of the configuration of an image forming apparatus equipped with a liquid dispensing device according to the first embodiment. [Figure 2] Figure 2 is a block diagram illustrating an example of the functional configuration of the control unit included in the image forming apparatus according to the first embodiment. [Figure 3] Figure 3 is a plan view illustrating the main parts of an example of a printing apparatus equipped with a liquid dispensing device according to the first embodiment. [Figure 4] Figure 4 is a side view illustrating the main parts of an example of a printing apparatus equipped with a liquid dispensing device according to the first embodiment. [Figure 5] Figure 5 is a plan view illustrating the main parts of another example of a liquid dispensing unit included in the liquid dispensing device according to the first embodiment. [Figure 6] Figure 6 is a front view illustrating another example of the liquid dispensing unit according to the first embodiment. [Figure 7] Figure 7 shows an example of the configuration of the liquid dispensing head included in the liquid dispensing device according to the first embodiment. [Figure 8] Figure 8 is a cross-sectional view taken along a direction perpendicular to the nozzle arrangement direction of the liquid discharge head of the image forming apparatus according to the first embodiment. [Figure 9] Figure 9 is a cross-sectional view of the liquid discharge head of the image forming apparatus according to the first embodiment, along line AA. [Figure 10] Figure 10 shows an example of the lower surface of a liquid discharge head in an image forming apparatus according to the first embodiment. [Figure 11] Figure 11 is a perspective view of the pressure chamber of a liquid discharge head according to the first embodiment. [Figure 12] Figure 12 is a cross-sectional view of the liquid discharge head according to the first embodiment, perpendicular to the nozzle arrangement direction and passing through the central position in the longitudinal direction of the pressure chamber. [Figure 13] Figure 13 is a plan view of the pressure chamber of the liquid discharge head according to the first embodiment. [Figure 14] Figure 14 is a diagram illustrating an example of a method for determining the number of empty droplets dispensed from the liquid dispensing head of an image forming apparatus according to the first embodiment. [Figure 15] Figure 15 is a diagram illustrating an example of a method for determining the number of empty droplets dispensed from the liquid dispensing head of an image forming apparatus according to the first embodiment. [Figure 16] Figure 16 is a diagram illustrating an example of a method for determining the number of empty droplets dispensed from a liquid dispensing head of an image forming apparatus according to the second embodiment. [Modes for carrying out the invention]

[0008] Embodiments of the liquid dispensing apparatus, image forming apparatus, and control method will be described in detail below with reference to the attached drawings.

[0009] (First Embodiment) Figure 1 is a diagram illustrating an example of the configuration of an image forming apparatus equipped with a liquid dispensing device according to the first embodiment. The image forming apparatus 200 includes a control unit 102, a head unit 103, an image inspection unit 104, an unwinder 105, a drying unit 106, and a rewinder 107.

[0010] The image forming apparatus 200 ejects ink onto paper P1 to form an image. Here, paper P1 is an example of a recording medium, and may be, for example, roll paper. Also, ink is an example of a droplet (liquid). In Figure 1, direction J is perpendicular to the width direction of paper P1 and indicates the direction from the supply side to the discharge side of paper P1 within the image forming apparatus 200. The width direction is perpendicular to the plane of the paper in Figure 1.

[0011] The control unit 102 is a control device that controls the image forming apparatus 200. The unwinder 105 and the rewinder 107 are synchronized by a control signal T1 output by the control unit 102 and convey the paper P1 at a predetermined speed. The unwinder 105, the rewinder 107, and the plurality of conveying rollers 108 constitute a conveying mechanism 150.

[0012] The head unit 103 includes a line head 131, a line head 132, a line head 133, and a line head 134. Each of the line heads 131 to 134 is an example of a liquid ejection head.

[0013] When the paper P conveyed by the unwinder 105 and the rewinder 107 passes directly below the head unit 103, each of the line heads 131 to 134 ejects ink based on image information and applies the ink onto the paper P1 to form an image. As an example, the line head 131 can eject black ink, the line head 132 can eject cyan ink, the line head 133 can eject magenta ink, and the line head 134 can eject yellow ink.

[0014] The drying unit 106 is a heating drum that heats the ink applied onto the paper P1 by the head unit 103 while conveying the paper P1. The drying unit 106 can evaporate liquid components such as moisture in the ink by heating, fix the ink onto the paper P1, and fix the image onto the paper P1.

[0015] The image inspection unit 104 reads the image fixed on the paper P1 and inspects the image. The control unit 102 can receive a reception signal T2 including image inspection data and the like from the image inspection unit 104 and perform various correction processes using the image inspection data.

[0016] The image forming apparatus 200 can have other functional parts added as appropriate, in addition to the configuration shown in Figure 1. For example, a pre-processing unit can be added between the unwinder 105 and the head unit 103 to perform pre-processing before image formation, or a post-processing unit can be added between the drying unit 106 and the rewinder 107 to perform post-processing before image formation. The pre-processing unit includes a processing liquid application process, such as applying a processing liquid to the paper P1 to suppress bleeding by reacting with the ink, but there are no particular restrictions on the content of the pre-processing. The post-processing unit also includes a cooling mechanism for cooling the paper, but there are no particular restrictions on the content of the post-processing.

[0017] Next, with reference to Figure 2, the functional configuration of the control unit 102 of the image forming apparatus 200 will be described. Figure 2 is a block diagram illustrating an example of the functional configuration of the control unit of the image forming apparatus according to the first embodiment.

[0018] As shown in Figure 2, the control unit 102 includes a temperature control unit 501, a transport speed control unit 502, a head ejection control unit 503, and an image inspection device control unit 504. The control unit 102 can realize these functions by having the CPU (Central Processing Unit) load a program stored in ROM (Read Only Memory) or the like into RAM (Random Access Memory) and execute it.

[0019] The temperature control unit 501 controls the temperature of the drying unit 106. The transport speed control unit 502 is an example of a moving unit that moves the head unit 103 and the paper P1 relative to each other in the transport direction. The transport speed control unit 502 controls the transport speed of the transport mechanism 150, which consists of an unwinder 105, a rewinder 107, and transport rollers 108, etc. The head ejection control unit 503 outputs a drive voltage waveform to eject ink from each of the line heads 131 to 134. The image inspection device control unit 504 controls the image inspection unit 104.

[0020] When performing image formation, the temperature control unit 501 starts temperature control so that the drying unit 106 reaches the desired temperature. The transport speed control unit 502 starts transporting the paper P1 to coincide with the timing when the drying unit 106 reaches the desired temperature and is ready for image formation. When the transport speed of the paper P1 by the transport speed control unit 502 becomes approximately constant and the drying unit 106 is within the desired temperature range, the head ejection control unit 503 outputs a drive voltage waveform to each of the line heads 131 to 134 of the head unit 103 to eject ink. The image forming apparatus 200 can form an image on the paper P1 with the ink ejected from each of the line heads 131 to 134.

[0021] The ink ejection timing for each line head 131-134 is pre-optimized based on the landing position read by the image inspection unit 104 during the image formation process. The ink ejection timing can also be adjusted by performing an image inspection during image formation.

[0022] Next, other examples of the printing apparatus 500 equipped with the liquid dispensing device according to this embodiment will be described with reference to Figures 3 and 4. Figure 3 is a plan view illustrating the main parts of an example of a printing apparatus equipped with the liquid dispensing device according to the first embodiment, and Figure 4 is a side view illustrating the main parts of an example of a printing apparatus equipped with the liquid dispensing device according to the first embodiment.

[0023] This printing apparatus 500 is a serial type apparatus, and the carriage 403 reciprocates in the main scanning direction K by the main scanning movement mechanism 493. The main scanning movement mechanism 493 includes a guide member 401, a main scanning motor 405, a timing belt 408, etc. The guide member 401 is stretched across the left and right side plates 491A and 491B and holds the carriage 403 in a movable position. The carriage 403 is then reciprocated in the main scanning direction K by the main scanning motor 405 via the timing belt 408 stretched between the drive pulley 406 and the driven pulley 407.

[0024] The carriage 403 is equipped with a liquid ejection unit 300 that integrates a liquid ejection head 100 and a head tank 441. The liquid ejection head 100 of the liquid ejection unit 300 ejects inks of various colors, such as yellow (Y), cyan (C), magenta (M), and black (K). The liquid ejection head 100 has a nozzle row consisting of multiple nozzles arranged in a sub-scanning direction L perpendicular to the main scanning direction K, and is mounted with the ejection direction facing downwards. The main scanning direction K is the direction X in the liquid ejection head described above, and the sub-scanning direction L is the direction Y in the liquid ejection head described above.

[0025] The printing apparatus 500 includes a transport mechanism 495 for transporting paper 410. The transport mechanism 495 includes a transport belt 412, which is a transport means, and a sub-scanning motor 416 for driving the transport belt 412.

[0026] The conveyor belt 412 picks up the paper 410 and transports it to a position opposite the liquid discharge head 100. This conveyor belt 412 is an endless belt and is stretched between the conveyor roller 413 and the tension roller 414. Pickup can be performed by electrostatic attraction or air suction, etc.

[0027] Then, the conveyor belt 412 moves in a circular motion in the sub-scanning direction L as the conveyor rollers 413 are rotationally driven by the sub-scanning motor 416 via the timing belt 417 and timing pulley 418.

[0028] Furthermore, a maintenance and recovery mechanism 420 for maintaining and recovering the liquid discharge head 100 is positioned on one side of the carriage 403 in the main scanning direction K, next to the conveyor belt 412.

[0029] The maintenance and recovery mechanism 420 consists of, for example, a cap member 421 that caps the nozzle surface (the surface on which the nozzle is formed) of the liquid discharge head 100, a wiper member 422 that wipes the nozzle surface, and the like.

[0030] The main scanning movement mechanism 493, the maintenance and recovery mechanism 420, and the transport mechanism 495 are mounted on a housing that includes side plates 491A, 491B, and a back plate 491C.

[0031] In the printing apparatus 500 configured in this way, the paper 410 is fed onto the transport belt 412 and picked up, and the paper 410 is transported in the sub-scanning direction L by the circumferential movement of the transport belt 412.

[0032] Therefore, by moving the carriage 403 in the main scanning direction K and driving the liquid ejection head 100 in accordance with the image signal, liquid is ejected onto the stationary paper 410 to form an image.

[0033] Next, with reference to Figure 5, another example of the liquid dispensing unit according to this embodiment will be described. Figure 5 is a plan view illustrating the main parts of another example of the liquid dispensing unit included in the liquid dispensing device according to the first embodiment.

[0034] The liquid discharge unit 300 comprises a housing portion consisting of side plates 491A, 491B and a back plate 491C, a main scanning movement mechanism 493, a carriage 403, and a liquid discharge head 100, which are components of the liquid discharge device.

[0035] Furthermore, a liquid dispensing unit can also be constructed by attaching the aforementioned maintenance and recovery mechanism 420 to, for example, the side plate 491B of the liquid dispensing unit 300.

[0036] Next, with reference to Figure 6, yet another example of the liquid dispensing unit according to this embodiment will be described. Figure 6 is a front view illustrating another example of the liquid dispensing unit according to the first embodiment.

[0037] This liquid discharge unit 300 includes a liquid discharge head 100 to which a flow path component 444 is attached, and a tube 456 connected to the flow path component 444.

[0038] The flow path component 444 is located inside the cover 442. A head tank 441 (see Figure 4) can be included instead of the flow path component 444. Furthermore, a connector 443 for electrical connection to the liquid discharge head 100 is provided on the upper part of the flow path component 444.

[0039] In this embodiment, the liquid discharged from the liquid discharge head 100 is not particularly limited, as long as it has a viscosity or surface tension that allows it to be discharged from the head, but it is preferable that its viscosity becomes 30 mPa·s or less at room temperature and atmospheric pressure, or when heated or cooled. More specifically, it is a solution, suspension, emulsion, etc. containing a solvent such as water or an organic solvent, a colorant such as a dye or pigment, a polymerizable compound, a resin, a functional material such as a surfactant, a biocompatible material such as DNA, an amino acid or protein, calcium, an edible material such as a natural pigment, etc. These can be used, for example, as inkjet inks, surface treatment liquids, components of electronic elements or light-emitting elements or liquids for forming electronic circuit resist patterns, and material liquids for 3D molding.

[0040] The energy source for discharging liquid includes piezoelectric actuators (multilayer piezoelectric elements and thin-film piezoelectric elements), thermal actuators using electrothermal conversion elements such as heating resistors, and electrostatic actuators consisting of a diaphragm and a counter electrode.

[0041] The liquid discharge unit 300 integrates functional components and mechanisms with the liquid discharge head 100 and includes an assembly of parts related to liquid discharge. For example, the liquid discharge unit 300 may include a combination of the liquid discharge head with at least one of the following components: a head tank, carriage, supply mechanism, maintenance and recovery mechanism, and main scanning movement mechanism 493.

[0042] Here, integration includes, for example, cases where the liquid dispensing head 100 and functional components and mechanisms are fixed to each other by fastening, bonding, engaging, etc., or where one is held movably relative to the other. Furthermore, the liquid dispensing head 100 and functional components and mechanisms may be configured to be detachable from each other.

[0043] For example, a liquid discharge unit 300 may have a liquid discharge head 100 and a head tank 441 integrated into one unit. Alternatively, the liquid discharge head 100 and head tank 441 may be integrated by being connected to each other with tubes or the like. In these liquid discharge units 300, a unit including a filter can also be added between the head tank 441 and the liquid discharge head 100.

[0044] Furthermore, some liquid dispensing units 300 integrate a liquid dispensing head 100 and a carriage 403 into a single unit.

[0045] Furthermore, some liquid discharge units 300 have a liquid discharge head 100 that is movably held by a guide member that constitutes part of the scanning movement mechanism 493, thereby integrating the liquid discharge head 100 and the scanning movement mechanism 493. Others have a liquid discharge head 100, carriage 403, and main scanning movement mechanism 493 integrated together.

[0046] Furthermore, in some liquid discharge units 300, a cap member, which is part of the maintenance and recovery mechanism 420, is fixed to a carriage 403 to which a liquid discharge head 100 is attached, thereby integrating the liquid discharge head 100, carriage 403, and maintenance and recovery mechanism 420.

[0047] Furthermore, some liquid discharge units 300 have a head tank 441 or a flow path component 444 attached to a liquid discharge head 100 to which a tube is connected, integrating the liquid discharge head 100 with the supply mechanism.

[0048] The main scanning movement mechanism 493 includes the guide member alone. The supply mechanism also includes the tube alone and the loading section alone.

[0049] Although embodiments have been described above, the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the present invention.

[0050] In this embodiment, the liquid dispensing device comprises a liquid dispensing head 100 or a liquid dispensing unit 300, and is a device that drives the liquid dispensing head 100 to dispense liquid. The liquid dispensing device includes not only devices that can dispense liquid onto objects to which liquid can adhere, but also devices that dispense liquid into air or into liquid.

[0051] This liquid dispensing device may also include means for feeding, conveying, and dispensing paper onto materials to which liquid can adhere, as well as pre-treatment devices, post-treatment devices, and the like.

[0052] For example, liquid ejection devices include image forming machines, which eject ink to form images on paper, and three-dimensional molding machines, which eject molding liquid onto a powder layer formed in layers to create three-dimensional objects.

[0053] Furthermore, liquid dispensing devices are not limited to those that visualize meaningful images such as letters or figures through the dispensed liquid. For example, they also include devices that form patterns that do not have meaning in themselves, or devices that create three-dimensional images.

[0054] The above-mentioned "materials to which liquid can adhere" refers to materials to which liquid can adhere, at least temporarily, including materials that adhere and solidify, or materials that adhere and penetrate. Specific examples include recording media such as paper, recording paper, film, and cloth; electronic components such as electronic circuit boards and piezoelectric elements; powder layers; organ models; and inspection cells. Unless otherwise specified, it includes all materials to which liquid can adhere.

[0055] The materials to which the liquid can adhere include paper, thread, fibers, fabrics, leather, metal, plastic, glass, wood, ceramics, etc., as long as the liquid can adhere to them, even temporarily.

[0056] Furthermore, liquid dispensing devices include those in which the liquid dispensing head and the surface to which the liquid can adhere move relative to each other, but are not limited to these. Specific examples include serial-type devices in which the liquid dispensing head moves, and line-type devices in which the liquid dispensing head does not move.

[0057] Other liquid dispensing devices include processing liquid coating devices that dispense processing liquid onto the surface of paper for purposes such as modifying the paper surface, and injection granulation devices that granulate fine particles of raw materials by spraying a compositional liquid, in which raw materials are dispersed in a solution, through a nozzle.

[0058] In this embodiment, the terms image formation, recording, printing, copying, printing, and shaping are all synonymous.

[0059] Figure 7 shows an example of the configuration of a liquid dispensing head in a liquid dispensing device according to the first embodiment. In the following description, an example of the configuration of the liquid dispensing head 100 will be described, but line heads 131 to 134 will be assumed to have a similar configuration. In this embodiment, as shown in Figure 7, the liquid dispensing head 100 includes a nozzle plate 1, a flow channel plate 2 which is an individual flow channel member, a diaphragm member 3 which is a wall member, a piezoelectric actuator 11 (see Figure 8), a common liquid chamber member 20, a supply port 28, and a head cover 29. The nozzle plate 1, the flow channel plate 2, and the diaphragm member 3 are laminated and bonded together. The piezoelectric actuator 11 (see Figure 8) displaces the deformable portion 30 (see Figure 8) of the diaphragm member 3. The head cover 29 also serves as a frame member of the liquid dispensing head 100. The supply port 28 supplies ink as a liquid to the common supply channel in the common liquid chamber member 20.

[0060] Figure 8 is a cross-sectional view of the liquid ejection head of the image forming apparatus according to the first embodiment, taken along a direction perpendicular to the nozzle arrangement direction. Figure 9 is a cross-sectional view of the liquid ejection head of the image forming apparatus according to the first embodiment, taken along line AA. In this embodiment, as shown in Figures 8 and 9, the nozzle plate 1 has a plurality of nozzle holes 4 for ejecting ink.

[0061] The fluid resistance section 7 and the intermediate supply channel 8 are defined by the flow path plate 2 and the vibrating plate member 3. Furthermore, the nozzle plate 1, the flow path plate 2, and the vibrating plate member 3 define multiple pressure chambers 6. Each pressure chamber 6 communicates with the nozzle hole 4. The fluid resistance section 7 is an individual flow path connected to each pressure chamber 6. The intermediate supply channel 8 is a liquid introduction section leading to one or more (one in this embodiment) fluid resistance sections 7.

[0062] The diaphragm member 3 is constructed by laminating multiple plate materials, and in this embodiment, it is constructed by laminating two metal plates. The diaphragm member 3 also has a deformable portion 30 that faces the piezoelectric actuator 11.

[0063] The deformable portion 30 constitutes a part of the wall surface of the pressure chamber 6 and is elastically deformable by the piezoelectric actuator 11. The piezoelectric actuator 11 includes an electromechanical conversion element as a driving means (actuator means, pressure generating means). In this embodiment, the deformable portion 30 has fewer laminated plates and a shorter length in the thickness direction than the other parts of the diaphragm member 3. Specifically, the deformable portion 30 is made of a single metal plate. Alternatively, the diaphragm member 3 may be partially deformable by making cuts in it, and the portion of this deformable part that constitutes the wall surface of the pressure chamber 6 may be designated as the deformable portion 30.

[0064] This piezoelectric actuator 11 has a piezoelectric member bonded to a base member 13, and grooves are machined into the piezoelectric member by half-cut dicing to form a required number of columnar piezoelectric elements 12 at predetermined intervals in a comb-like shape in the nozzle arrangement direction.

[0065] A support member 27 is provided at the upper part of the deformable portion 30 to support the deformable portion 30. The piezoelectric element 12 is joined to the support member 27.

[0066] This piezoelectric element 12 is constructed by alternately stacking piezoelectric layers and internal electrodes. In the piezoelectric element 12, each internal electrode is drawn out to the end face and connected to an external electrode (end face electrode), and a flexible wiring member 15 is connected to the external electrode.

[0067] The common liquid chamber member 20 forms a common liquid chamber 10 that leads to a plurality of pressure chambers 6. The common liquid chamber 10 communicates with the intermediate supply channel 8 through an opening 9 provided in the diaphragm member 3, and is connected to the fluid resistance section 7 via the intermediate supply channel 8.

[0068] The ink in the common liquid chamber 10 is supplied to the pressure chamber 6 via the intermediate supply channel 8 and the fluid resistance section 7. The ink in the pressure chamber 6 is ejected from the nozzle hole 4 to the outside of the liquid discharge head 100. In the pressure chamber 6, the direction of ink supply is from the fluid resistance section 7 side in the X direction to the nozzle hole 4 side.

[0069] In this liquid dispensing head 100, for example, the piezoelectric element 12 contracts by lowering the voltage applied to it from a reference potential (intermediate potential). This contraction of the piezoelectric element 12 causes the deformation portion 30 to deform toward the piezoelectric element 12, expanding the volume of the pressure chamber 6, which in turn causes ink to flow into the pressure chamber 6.

[0070] Subsequently, the voltage applied to the piezoelectric element 12 is increased, causing the piezoelectric element 12 to stretch in the stacking direction, thereby deforming the deformed portion 30 toward the nozzle hole 4 and contracting the volume of the pressure chamber 6. As a result, the ink in the pressure chamber 6 is pressurized, and the ink is ejected from the nozzle hole 4.

[0071] The liquid ejection head 100 of this embodiment is a non-circulating type liquid ejection head. In a circulating type liquid ejection head, the ink that flows into the pressure chamber 6 is circulated through a circulation channel or the like and flows back into the pressure chamber 6, but in the non-circulating type liquid ejection head 100 of this embodiment, such ink circulation is not performed. The pressure chamber 6 of this liquid ejection head 100 is provided with two openings: a nozzle hole 4 and a fluid resistance section 7.

[0072] Figure 10 shows an example of the lower surface of a liquid discharge head in an image forming apparatus according to the first embodiment. The liquid discharge head 100 may have a configuration having one row of nozzles in which nozzle holes 4 are arranged, as shown in Figure 10(a), or it may have a configuration having multiple rows of nozzles, as shown in Figure 10(b). In addition, as shown in Figure 10(b), the nozzle rows may be arranged in parallel, or in a staggered pattern, etc. Also, as shown in Figure 10(c), a head unit 103 may be formed by arranging multiple liquid discharge heads 100. Also, as shown in Figure 10(d), a pair of adjacent liquid discharge heads 100 may be arranged in a staggered pattern within the head unit 103. Furthermore, the arrangement of nozzle holes 4 and liquid discharge heads 100 is not limited to these, and the optimal arrangement can be selected as appropriate.

[0073] Next, the configuration of the pressure chamber 6 in the first embodiment will be described using Figures 11 to 13. Figure 11 is a perspective view of the pressure chamber of the liquid discharge head according to the first embodiment. Figure 12 is a cross-sectional view of the liquid discharge head according to the first embodiment, perpendicular to the nozzle arrangement direction and passing through the center of the longitudinal direction of the pressure chamber. Figure 13 is a plan view of the pressure chamber of the liquid discharge head according to the first embodiment.

[0074] As shown in Figures 11-13, in this embodiment, the pressure chamber 6 has a cross section E1 on the nozzle hole 4 side in the longitudinal direction X of the pressure chamber 6 that is wider than the cross section E2 on the opposite side. Specifically, the pressure chamber 6 has a step 6a in the middle of its longitudinal direction X. Due to this step 6a, the area of ​​the cross section E1 perpendicular to the longitudinal direction X on the nozzle hole 4 side of the pressure chamber 6 is larger than the area of ​​the cross section E2 perpendicular to the longitudinal direction X on the opposite side of the nozzle hole 4 side. In this embodiment, in particular, as shown in Figure 11, among the cross sections E1 and E2 of the pressure chamber 6 perpendicular to the longitudinal direction X, including the deformed portion 30, if the cross section E1 closest to the central position 4a in the longitudinal direction X of the pressure chamber 6 is designated as the first cross section E1, and the cross section E2 furthest from the central position 4a is designated as the second cross section E2, then the area of ​​the first cross section E1 is larger than the area of ​​the second cross section E2. In other words, in this embodiment, the pressure chamber 6 with the largest cross-sectional area perpendicular to the ink flow direction (longitudinal direction X) is located closest to the nozzle hole 4 in the ink flow direction. In this embodiment, the volume of the pressure chamber 6 is preferably 10 nL or less. This makes it possible to reduce Tc.

[0075] Furthermore, as shown in Figure 12, the pressure chamber 6 is a range that includes the deformed portion 30 in the longitudinal direction X, with the position closest to the central position 4a of the nozzle hole 4 in the longitudinal direction X being defined as the first longitudinal position Xa, and the position furthest from it being defined as the second longitudinal position Xb. If the length of the pressure chamber 6 in the Z direction at the first longitudinal position Xa is defined as the first length Z1, and the length of the pressure chamber 6 in the Z direction at the second longitudinal position Xb is defined as the second length Z2, then the first length Z1 is provided to be greater than the second length Z2. As in this embodiment, the position closest to the central position 4a of the nozzle hole 4 in the longitudinal direction X may be the same position as the central position 4a in the longitudinal direction X.

[0076] Figures 14 and 15 illustrate an example of a method for determining the number of empty droplets ejected from the liquid ejection head of an image forming apparatus according to the first embodiment. In this embodiment, the head ejection control unit 503 performs image forming ejection after empty ejection. Here, empty ejection is an example of a first ejection in which ink that does not form an image (an example of a first liquid) is ejected from the nozzle hole 4. Empty ejection is performed, for example, immediately before ejection of ink for image formation, to remove ink whose viscosity has changed due to evaporation of moisture etc. in the nozzle hole 4, by ejecting ink into the non-image forming area of ​​the object to be printed or the area for empty ejection. Image forming ejection is an example of a second ejection in which ink that forms an image (an example of a second liquid) is ejected from the nozzle hole 4.

[0077] Incidentally, the thickening of ink due to drying caused by the evaporation of moisture from the nozzle meniscus at the nozzle hole 4 spreads by diffusion from the ink near the nozzle hole 4. Therefore, the thickening of ink due to drying caused by the evaporation of moisture from the nozzle meniscus is particularly likely to occur in the part of the pressure chamber 6 with a large cross-sectional area. Accordingly, as shown in Figure 14, in a liquid ejection head 100 (inkjet head, etc.) in which the cross-sectional area near the nozzle hole 4 is larger than that of the other parts of the multiple pressure chambers 6, it is preferable that the number of ink droplets ejected during the dry ejection operation after standing is greater than the volume of the part of the multiple pressure chambers 6 with a large cross-sectional area. This makes it possible to replace the ink in the part where thickening is particularly likely to occur due to drying caused by the evaporation of moisture from the nozzle meniscus with fresh ink, and enables ejection with less delay without using flow-through technology. As a result, fast-drying ink can be stably ejected using a simple and inexpensive inkjet head and control system.

[0078] Specifically, the head ejection control unit 503 determines the number of ink droplets to be ejected by dry ejection to be the number of droplets of liquid exceeding the volume of a pressure chamber 6 among the multiple pressure chambers 6 whose cross-sectional area perpendicular to the ink flow direction (longitudinal direction X) from the fluid resistance section 7 to the nozzle hole 4 is greater than a predetermined cross-sectional area. Here, the predetermined cross-sectional area is a pre-set cross-sectional area, and is at least greater than the cross-sectional area of ​​the pressure chamber 6 among the multiple pressure chambers 6 whose cross-sectional area perpendicular to the ink flow direction is smallest. By performing dry ejection of the number of droplets determined in this way, it is possible to replace the ink in parts where ink viscosity is particularly likely to occur due to the drying effect of ink due to evaporation of moisture etc. from the nozzle meniscus with fresh ink. As a result, ink ejection with less delay can be performed. In particular, when the ink ejected from the nozzle hole 4 is an ink containing water, organic solvents, and pigments, the nozzle hole 4 is more prone to clogging due to drying and viscosity than with dye ink. However, with the liquid ejection head 100 according to this embodiment, it is possible to realize a system using water-based pigment ink that has good image quality and high productivity due to its fast drying properties.

[0079] In this embodiment, the head ejection control unit 503 determines the number of ink droplets to be ejected by dry ejection to be greater than the volume of the pressure chamber 6, which has the largest cross-sectional area perpendicular to the ink flow direction. This allows for the ejection of ink, especially in areas where viscosity tends to increase, with a smaller amount of dry ejection ink. As a result, ink ejection can be performed with less delay while reducing the cost of ink consumed by dry ejection.

[0080] For example, the head ejection control unit 503 determines the number of ink droplets N for empty ejection using the following equation (1).

number

[0081] Thus, according to the image forming apparatus of the first embodiment, ejection with less delay can be performed without using flow-through technology, and therefore, fast-drying ink can be stably ejected using a simple and inexpensive inkjet head and control system.

[0082] (Second Embodiment) This embodiment is an example in which the cross-sectional area of ​​multiple pressure chambers changes multiple times from the upstream side to the downstream side in the ink flow direction, due to steps provided below the direction of gravity during ink ejection. In the following description, the same configuration as in the first embodiment will be omitted.

[0083] In this embodiment, the cross-sectional area of ​​the multiple pressure chambers 6 in directions perpendicular to the longitudinal direction X (Y and Z directions) is changed by multiple steps provided downward relative to the direction of gravity during ink discharge, from the upstream side to the downstream side in the ink flow direction (longitudinal direction X). As a result, since air bubbles that cause abnormal ink discharge accumulate upward due to gravity, forming the steps at the lower level prevents air bubbles from accumulating in the steps, thereby realizing a more stable liquid discharge head 100.

[0084] Figure 16 is a diagram illustrating an example of a method for determining the number of empty droplets discharged from a liquid discharge head in an image forming apparatus according to the second embodiment. Here, we will explain a method for determining the number of empty droplets discharged when there are n steps 6a between multiple pressure chambers 6, and the cross-sectional area of ​​the pressure chambers 6 changes multiple times.

[0085] The head dispensing control unit 503 determines the number of drops N for empty dispensing for any i between 1 ≤ i ≤ n using the following equation (2).

[0086]

number

[0087] Furthermore, the method for calculating the volume of the stepped portion (the region between the j-th step and the (j-1)th step) is not limited to the above formula (2). If the shape of the liquid chamber (pressure chamber) is not a combination of cubes, the volume of the stepped portion should naturally be calculated using a method appropriate for calculating the volume of that solid. For example, if the pressure chamber 6 is formed by a press molding process and is circular, or if it is formed by anisotropic etching of silicon and is polygonal, the volume is calculated by the product of the area and height of the circle or polygon.

[0088] Thus, according to the image forming apparatus of the second embodiment, since air bubbles that cause abnormal ink ejection accumulate upward due to gravity, forming a step 6a on the lower level prevents air bubbles from accumulating in the step 6a, thereby realizing a more stable liquid ejection head 100.

[0089] In the above embodiment, the image forming apparatus of the present invention is described using an example in which it is applied to a multifunction device having at least two functions from among a copy function, a printer function, a scanner function, and a facsimile function. However, it can be applied to any image forming apparatus such as a copier, printer, scanner, or facsimile device. [Explanation of Symbols]

[0090] 1 Nozzle plate 2 Flow channel plate 3. Diaphragm component 4 nozzle holes 6. Pressure Chamber 7 Fluid resistance section 8. Intermediate supply channel 9 Opening 10 Common liquid chamber 11. Piezoelectric Actuator 12 Piezoelectric element 13 Base member 20 Common liquid chamber member 27 Support Member 28 supply ports 29 Headcovers 30 Deformed part 100 liquid dispensing heads 102 Control Unit 200 Image forming apparatus 500 printing equipment 503 Head Discharge Control Unit [Prior art documents] [Patent Documents]

[0091] [Patent Document 1] Japanese Patent Publication No. 2018-103616

Claims

1. A nozzle opening for discharging liquid, Multiple pressure chambers communicating with the nozzle hole, A fluid resistance section connected to the pressure chamber, The system comprises a control unit that discharges a first liquid that does not perform image formation from the nozzle hole, and then discharges a second liquid that performs image formation from the nozzle hole, A liquid dispensing device in which the number of drops of the first liquid to be dispensed is the number of drops of liquid at the point when the volume of the pressure chamber, among the plurality of pressure chambers, whose cross-sectional area perpendicular to the direction of liquid flow from the fluid resistance portion to the nozzle hole is greater than a predetermined cross-sectional area.

2. The liquid discharge device according to claim 1, wherein the pressure chamber with the largest cross-sectional area is located closest to the nozzle hole in the flow direction.

3. The liquid dispensing device according to claim 1, wherein the number of drops of the first liquid to be dispensed is the number of drops of liquid at the point when the volume of the pressure chamber with the largest cross-sectional area among the plurality of pressure chambers is exceeded.

4. The liquid discharge device according to claim 1, wherein the cross-sectional area of ​​the plurality of pressure chambers changes from the upstream side to the downstream side in the flow direction due to a step provided below the direction of gravity when the liquid is discharged.

5. The liquid dispensing device according to claim 1, wherein the volume of the pressure chamber is 10 nL or less.

6. The liquid dispensing apparatus according to claim 1, wherein the liquid dispensed from the nozzle hole is an ink containing water, an organic solvent, and a pigment.

7. An image forming apparatus comprising the liquid dispensing device described in claim 1.

8. A control method for a liquid discharge device comprising at least one nozzle hole for discharging liquid, a plurality of pressure chambers communicating with the nozzle hole, and a fluid resistance section connected to the pressure chambers, A first discharge step in which a first liquid that does not undergo image formation is discharged from the nozzle hole, The process includes, after the first dispensing step, a second dispensing step in which a second liquid for image formation is dispensed from the nozzle hole, A control method in which the number of drops of the first liquid to be discharged is the number of drops of liquid at the point when the volume of the pressure chamber among the plurality of pressure chambers, the pressure chamber whose cross-sectional area perpendicular to the direction of liquid flow from the fluid resistance portion to the nozzle hole is greater than a predetermined cross-sectional area, is exceeded.

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