Liquid dispensing head and image forming apparatus

Abstract

The present invention provides a liquid discharge head that suppresses pressure fluctuations by providing a tank in the supply flow path, and in which bubbles generated in the tank are discharged downstream only by the forward circulation of the liquid. [Solution] The liquid discharge head of the present invention comprises a plurality of nozzles for discharging liquid, a supply channel connected to the nozzles, and a supply tank connected upstream of the nozzles in the direction of liquid flow in the supply channel, wherein the inlet of the supply tank into which the liquid flows from the supply channel is located lower in the direction of gravity than the outlet from which the liquid is discharged from the supply tank toward the nozzles.

Description

Technical Field

[0001] This invention relates to a liquid ejection head and an image forming apparatus including the liquid ejection head.

Background Art

[0002] An image forming apparatus using an inkjet head that forms an image by ejecting a liquid such as ink from a nozzle is widely known. In such an inkjet head, for the purpose of suppressing pressure fluctuations of the liquid due to ejection, a technique of providing an ink tank having a damper function in front of the nozzle to stabilize ejection is known. When there is no such damper function, the meniscus pressure fluctuation of the ink at the nozzle becomes large, the droplet volume decreases, and image abnormalities called transient streaks are likely to occur in the formed image. However, it has been found that simply providing an ink tank stabilizes the flow rate, but bubbles may occur at the upper part or corners of the tank during the initial filling of the ink. In a general inkjet head, since the nozzle is located below, the direction of the ink flow also often goes downward. However, since bubbles go upward in the liquid, natural discharge is difficult.

[0003] Now, since such bubbles cause image abnormalities if not removed, techniques for easily discharging the generated bubbles and techniques for preventing the generation of bubbles in the first place have been developed (see, for example, Patent Documents 1, 2, etc.). However, in the conventional method, it is necessary to circulate the ink in the reverse direction during discharge to discharge the bubbles from the supply side port, and there has been a problem that the initial filling takes time.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention aims to solve these problems by providing a liquid discharge head that suppresses pressure fluctuations by providing a tank in the supply channel, and in which bubbles generated in the tank are discharged downstream only by forward circulation of the liquid. [Means for solving the problem]

[0005] The liquid discharge head of the present invention comprises a plurality of nozzles for discharging liquid, a supply channel connected to the nozzles, and a supply tank connected upstream of the nozzles in the direction of liquid flow in the supply channel, wherein the inlet of the supply tank into which the liquid flows from the supply channel is located lower in the direction of gravity than the outlet from which the liquid is discharged from the supply tank toward the nozzles. [Effects of the Invention]

[0006] According to the present invention, pressure fluctuations can be suppressed by providing a tank in the supply channel, and bubbles generated in the tank can be discharged downstream solely by the forward circulation of the liquid. [Brief explanation of the drawing]

[0007] [Figure 1] This figure shows an example of the configuration of the liquid dispensing head of the present invention. [Figure 2] This figure shows an example of the nozzle configuration of the liquid discharge head shown in Figure 1. [Figure 3] This is a magnified view of the flow path structure of the liquid discharge head shown in Figure 1. [Figure 4] This figure shows the generation and movement of bubbles in the liquid dispensing module shown in Figure 3. [Figure 5] This diagram shows a conventional example of a liquid dispensing head. [Figure 6] This figure shows an example of how bubbles are discharged in the liquid dispensing head of the present invention. [Figure 7] This figure shows an example of the configuration of the damper structure of the present invention. [Figure 8]This figure shows an example of the pressure fluctuation suppression effect of the configuration of the present invention. [Figure 9] This figure shows an example of the configuration of the curvature section in the flow path of the present invention. [Figure 10] Figure 9 shows an example of the effect of curvature. [Figure 11] This figure shows an example of the configuration of the common flow path component of a liquid discharge head. [Figure 12] This diagram shows the positional relationship between the individual flow paths of the liquid discharge head and the nozzle holes. [Figure 13] Figure 12 is a schematic diagram of the configuration shown, viewed from the Z-direction. [Figure 14] This figure shows an example of the configuration of a liquid dispensing device according to the present invention. [Figure 15] This figure shows an example of the configuration of the liquid dispensing unit in the present invention. [Modes for carrying out the invention]

[0008] Figure 1 illustrates a liquid ejection head 10 as an inkjet head, representing a first embodiment of the present invention. In the following explanation, the nozzle arrangement direction (longitudinal direction of the liquid discharge head) will be referred to as the Y direction, the liquid discharge direction from the nozzle (height direction of the liquid discharge head) as the Z direction, and the direction perpendicular to both the X direction and the Z direction (short direction of the liquid discharge head) as the X direction.

[0009] The liquid discharge head 10 comprises a nozzle plate 14, a flow path member 15, and a cover 11 which serves as a housing member. A supply port 12 for supplying liquid ink Q is provided at one end of the flow path member 15 in the X direction, and a discharge port 13 for discharging ink Q is provided at the other end of the flow path member 15 in the Y direction. A connector 16 for communicating with the actuator 2 housed in the cover is provided on the upper part of the cover 11.

[0010] The nozzle plate 14, the flow path member 15, and the cover 11 are made of metal, resin, or ceramics. The cover 11 houses and supports a liquid discharge module 1 (see FIG. 3) described later inside. The flow path member 15 defines a flow path through which liquid flows, and the nozzle plate 14 has a plurality of nozzles for discharging a liquid such as a recording liquid. The nozzle plate 14 is mechanically fixed to the flow path member 15, and the cover 11 is mechanically (removably) fixed to a base 17 that holds the flow path member 15 and the nozzle plate 14.

[0011] FIG. 2 is a diagram for explaining an example of the nozzle arrangement of the nozzle plate 14. As shown in FIG. 2(a), one nozzle row may be provided at the center of the nozzle plate in the X direction (the short side direction of the head), or as shown in FIG. 2(b), the nozzles 14a may be arranged in a staggered pattern to provide two nozzle rows in the X direction. The nozzle arrangement shown in FIG. 2 is an example. For example, two sets of two nozzle rows arranged in a staggered pattern in the X direction may be provided, having a total of four nozzle rows, or a plurality of nozzle rows with the same position of the nozzles in the X direction (the short side direction of the head) may be provided.

[0012] In the present embodiment, ink Q is discharged from each nozzle 14a by the liquid discharge module 1, and the ink Q, which is the recording liquid, is deposited on a recording medium (e.g., paper) based on the image data from the control unit to form an image. In the present embodiment, the internal structure and configuration of each part up to the liquid discharge module 1 are not described, but it may have the structure of a general inkjet head.

[0013] FIG. 3 is a schematic cross-sectional view showing the internal structure of the flow path member 15 and the liquid discharge module 1. From the supply port 12, a liquid flow path 151, which is a supply flow path, is formed through the flow path member 15 to the discharge port 13. Along the liquid flow path 151, a supply tank 20, a nozzle hole 153 which is an opening formed at a position in contact with the nozzle plate 14, a first liquid chamber 154 which is a liquid chamber containing the nozzle hole 153, and a recovery tank 30 are provided, respectively, along the direction in which the ink Q flows. The liquid flow path 151 extending from the downstream side in Figure 3 is connected to the discharge port 13. The nozzle hole 153 is an opening provided on the bottom surface of the first liquid chamber 154 so as to align with the position of the nozzle 14a when the nozzle plate 14 is attached. Although not shown in Figure 3, multiple nozzle holes 153 may be formed along the Y direction, as illustrated in Figure 2. Furthermore, if there are multiple nozzle holes 153, it is desirable that the configuration be such that droplets are discharged from the nozzle holes 153 at opposing positions by the operation of actuators 2 arranged along the Y direction, which will be described later. Furthermore, an ink cartridge or the like is connected to the end of the discharge port 13, forming a loop that circulates ink Q from the supply side to the recovery side.

[0014] An actuator 2, such as a piezoelectric element, is positioned at the top of the first liquid chamber 154, opposite to the nozzle hole 153. The operation of this actuator 2 causes the volume of the first liquid chamber 154 to change, and ink Q is discharged as droplets from the nozzle hole 153 facing the actuator 2. Although actuator 2 has been described as a piezoelectric element here, it is not limited to this configuration, and any configuration that functions as a drive source for ejecting ink Q from the nozzle hole 153 is acceptable. Furthermore, the actuator 2 contracts and expands in response to electrical signals communicated via the connector 16, thereby changing the volume of the first liquid chamber 154. These electrical signals may be transmitted from the control unit of the image forming apparatus.

[0015] As shown in Figure 3, an inlet 21 is formed at the junction from the liquid flow path 151 to the supply tank 20. Similarly, an outlet 22 is formed at the junction between the supply tank 20 and the liquid flow path 151 leading towards the nozzle hole 153.

[0016] Furthermore, the supply tank 20 has a curved section 23 provided on the wall opposite to the inlet 21, and a curved section 24 provided on the wall opposite to the outlet 22. Both the curved sections 23 and 24 constitute a bent wall surface with a radius of curvature R1. This radius of curvature R1 may be set to any value, but most preferably it is the width in the Y direction of the supply tank 20 and the recovery tank 30, respectively. 20 , Y 30 It is desirable to set it to be approximately identical to the previous value. In other words, R1 ≈ Y 20 ≒Y 30 It is desirable that the system be designed in such a way. With this configuration, the corners and edges of the supply tank 20 and recovery tank 30 that could cause bubbles can be given a large curvature within a range that does not obstruct the flow of ink Q, thereby improving the bubble discharge performance of the supply tank 20 and recovery tank 30.

[0017] Furthermore, in the Z-direction, which is the direction of gravity, the inlet 21 is connected to the lower side and the outlet 22 is connected to the upper side. With this configuration, bubbles p are less likely to form than in the conventional configuration shown in Figure 4, and any bubbles p that do form are more easily discharged towards the outlet 22 side, i.e., in the forward direction of the flow, along with the flow of ink Q. Similarly, in the recovery tank 30, the inlet 31 connected from the nozzle hole 153 side is positioned lower than the outlet 32 ​​that flows to the discharge port 13.

[0018] I will explain this point in more detail. First, Figure 5 illustrates a comparison with conventional ink tanks, showing a case where a supply-side ink tank 40 and a recovery-side ink tank 50 are provided in the liquid flow path 151. In this case, the inside of the liquid ejection module 1 is usually very narrow, making it difficult to route the liquid flow path 151. Therefore, the inlet 41 of the supply-side ink tank 40 is located above the supply-side ink tank 40. In this case, as shown in Figures 5(b) and (c), when filling with ink Q from an empty state, an air pocket forms at the top, making it easy for air bubbles p to be generated. Furthermore, if the supply-side ink tank 40 is connected to the linear liquid flow path 151 in this manner, the bubbles p generated in the liquid flow path 151 will naturally accumulate on the inlet side 41 due to buoyancy. When these air bubbles p merge and enlarge, in extreme cases, as shown in Figures 5(d) and (e), the upper part of the supply-side ink tank 40 can be completely occupied by the air bubbles p. This makes it difficult to apply sufficient pressure due to reasons such as a decrease in the flow rate of ink Q, resulting in insufficient pressure at the nozzle holes 153 and poor image formation. When air pockets formed at the top in this way, a method was used to remove the air bubbles p by recirculating the ink Q in reverse. However, this process of repeatedly recirculating in reverse and forward directions had the problem of increasing the initial filling time.

[0019] On the other hand, according to the configuration of this embodiment, as already shown in Figure 3, the inlet 21 is provided to be located below the position of the outlet 22. Therefore, as shown in Figures 6(a) to (c), even if air bubbles p are generated when the supply tank 20 is filled, they are easily pushed out and flow out of the outlet 22. Similarly, in the recovery tank 30, the inlet 31, which is on the upstream side, is positioned lower than the outlet 32, so that the generated bubbles p are easily discharged in the forward direction toward the discharge port 13.

[0020] In other words, in the supply tank 20 and the recovery tank 30, the outlets 22 and 32 are positioned so that their openings are located at the very top of the supply tank 20 and the recovery tank 30, respectively. With this configuration, air pockets are less likely to form when filling with ink Q, air bubbles p are less likely to remain, and even if air bubbles p do form, the forward circulation of ink Q makes it easier for the air bubbles p to be expelled. With this configuration, a tank is provided in the supply channel to suppress pressure fluctuations, and bubbles p generated in the tank can be discharged downstream solely by the forward circulation of the liquid.

[0021] Furthermore, as shown in Figure 7, the supply tank 20 and the recovery tank 30 are each provided with a flexible cover 60 having a damper structure with a trapezoidal cross-sectional area when viewed from the side. Since the configuration of the flexible cover 60 is substantially the same for both the supply tank 20 and the recovery tank 30, this embodiment will only describe the flexible cover 60 attached to the supply tank 20.

[0022] As shown in Figure 7, the flexible cover 60 is provided such that the supply tank 20 has a trapezoidal cross-section when viewed from the side. In other words, the flexible cover 60 in this embodiment has an inclined surface 61 that approaches the outlet 22 side as the wall surface moves upward in the direction of gravity. Furthermore, in this embodiment, in order to ensure that the shape of the supply tank 20 is symmetrical, the opposite side is also provided with an inclined surface 62 that approaches the inlet 21 side. With such a flexible cover 60, even when a large amount of ink Q flows into the supply tank 20, the flexible cover 60 deforms in the ±X direction as shown in Figure 7, thereby suppressing the flow velocity of ink Q in the supply tank 20 as a whole and preventing sudden pressure fluctuations. Furthermore, if the wall surface of the flexible cover 60 forms an inclined surface 61 and approaches the outlet 22 side as it moves upward, the cross-sectional area S of the portion enclosed by the flexible cover 60 and the supply tank 20, indicated by the diagonal lines in the figure, decreases as it moves towards the outlet 22. This indicates that the volume of the portion enclosed by the supply tank 20 and the flexible cover 60 decreases as it moves upward. With this shape, the flow velocity of the ink Q flowing inside increases as it moves towards the outlet 22, which also has the effect of further promoting the discharge of air bubbles. Thus, the flexible cover 60, which is the damper structure of the supply tank 20, has a trapezoidal shape in which the upper cross-section becomes smaller as it moves upward in the direction of gravity, thereby increasing the effect of discharging air bubbles.

[0023] Figure 8 shows the presence or absence of a damping effect from the flexible cover 60, with time on the horizontal axis and pressure on the vertical axis, with a dotted line representing the case without a damping structure and a solid line representing the case with a damping structure. Furthermore, if the pressure fluctuation exceeds 2460 Pa, streaks may appear during printing. The threshold for such pressure fluctuations is also shown by a dashed line in Figure 8. As is clear from Figure 8, without a damper, pressure fluctuations may exceed 2460 Pa, and in such conditions, there is a risk of streaking. However, when the flexible cover 60, which has a damper structure, is provided, pressure fluctuations are kept below 2460 Pa at all times, and thus streaking is suppressed throughout the entire processing time.

[0024] Now, the bubbles p discharged by the combined effect of the flexible cover 60 and the supply tank 20 pass through the first liquid chamber 154 and move to the recovery tank 30, as shown in Figure 9. As already mentioned, in the recovery tank 30 as well, the inlet 31, which is upstream of the liquid flow path 151, is located downwards, and the outlet 32 ​​is located upwards. Therefore, in the recovery tank 30 as well, bubbles p are easily discharged and escape towards the discharge port 13.

[0025] Furthermore, as shown in Figure 9, each part forming the corners and edges of the liquid flow path 151 has a bent portion 151a at each corner. The walls of these bent portions 151a are configured such that their cross-section is a curved surface with a radius of curvature R2. This configuration prevents bubbles from being obstructed at corners and edges as they pass through the liquid channel 151, thereby improving bubble discharge efficiency.

[0026] Furthermore, as shown in Figure 10, each of the above configurations is effective not only during the initial filling of ink Q, but also when ink Q is discharged and ink cleaning is performed. Specifically, when air is introduced from the supply port 12 side to discharge the ink Q, there is a concern that, in the conventional example, the ink Q may remain in the corners and edges, as shown in Figure 10(a) as a comparative example. However, in this embodiment, where curved surfaces with a radius of curvature R1 are formed at the corners 23 and 24 of the supply tank 20, as shown in Figure 10(b), the ink Q tends to collect towards the inlet 21 or outlet 22 due to the curved sections 23 and 24, preventing it from accumulating in the corners. Furthermore, the lateral airflow entering from the inlet 21 is bent along the curvature of the curved section 23 and becomes an upward-flowing airflow, thus improving the discharge of ink Q compared to the comparative example shown in Figure 10(a), which simply has right-angle corners. Since the same effect applies to the wall surface of the curved portion 151a of the liquid flow path 151, a detailed explanation will be omitted.

[0027] Now, in the above-described embodiment, for the purpose of simplifying the explanation, the structure of the liquid ejection module 1 was described in a manner in which ink Q is ejected from a nozzle hole 153 opening in the first liquid chamber 154, but the configuration is not limited to this. Figure 11 also shows a specific example of the configuration of the flow path member 15 of the liquid discharge module 1. The flow channel member 15 has an upper structure 155 that has a first liquid chamber 154 inside, and a common flow channel member 156 located on the bottom surface of the upper structure 155, and a groove 157 formed in the common flow channel member 156 constitutes a flow channel for ink Q connecting the two upper structures 155. A nozzle hole 153 is provided as an opening on the bottom side of the common flow channel member 156, and the nozzle hole 153 is connected to the second liquid chamber 158 below. Figure 12 is a schematic perspective view showing the configuration of the common flow channel member 156 and its positional relationship with the second liquid chamber 158. A diaphragm 160 and individual flow channel members 170 are provided on the Z-direction side of the common flow channel member 156, and piezoelectric elements 161 are arranged on the diaphragm 160 in a positional relationship corresponding to the second liquid chamber 158. The second liquid chamber 158 is a small liquid chamber that functions as a reservoir for ink Q, and a piezoelectric element 161 is provided at a position corresponding to each of these second liquid chambers 158. With this configuration, ink Q is discharged from the nozzle 14a opening in the second liquid chamber 158 as the piezoelectric element 161 at the corresponding position contracts and expands, causing the volume of the second liquid chamber 158 to contract and expand.

[0028] As shown in Figure 12, from the first liquid chamber 154, grooves 157 formed in the common flow channel member 156 extend alternately as tributaries, and the flow channels of each nozzle 14a are formed by connecting from these alternate grooves 157. Therefore, for example, in Figure 13, which shows the liquid ejection module 1 viewed from the Z-side, a flow of ink Q is generated from the first liquid chamber 154 on the left side of the figure, through a branch groove 157, to the first liquid chamber 154 on the opposite side, and the nozzle 14a is opened in the middle of this flow path. In Figure 13, such a flow path is schematically shown with arrows.

[0029] In addition to the configurations listed here, there are various other configurations for the liquid dispensing head 10.

[0030] Such liquid ejection heads 10 are used in various liquid ejection devices, such as a printing device 500, which is an example of an image forming apparatus as shown in Figure 14. An example of a printing device will be explained with reference to Figures 14 and 15. Figure 14 is a side view of the main part of the device, and Figure 15 is a top view of the main part of the device.

[0031] This printing apparatus 500 is a serial type apparatus, and the carriage 403 reciprocates in the main scanning direction by the main scanning movement mechanism 493 shown in Figure 15. 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 by the main scanning motor 405 via the timing belt 408 stretched between the drive pulley 406 and the driven pulley 407.

[0032] The carriage 403 is equipped with a liquid ejection unit 440, which includes a liquid ejection head 10 according to the present invention and an ink tank 205 for supplying ink to the liquid ejection head 10. The liquid ejection head 10 of the liquid ejection unit 440 ejects liquids of yellow (Y), cyan (C), magenta (M), and black (K) as ink Q, according to the connected ink tank 205. The liquid ejection head 10 is mounted with a nozzle row consisting of multiple nozzles arranged in a sub-scanning direction perpendicular to the main scanning direction, and with the ejection direction facing downward.

[0033] The liquid ejection head 10 is connected to the ink tank 205, and as already mentioned, the required color of liquid is circulated and supplied as ink Q.

[0034] This printing apparatus 500 is equipped with a transport mechanism for transporting paper 410 as a recording medium. The transport mechanism includes a transport belt 412, which is a transport means, and a sub-scanning motor 416 for driving the transport belt 412.

[0035] The conveyor belt 412 attracts the paper 410 and transports it to a position opposite the liquid discharge head 10. This conveyor belt 412 is an endless belt and is stretched between the conveyor roller 413 and the tension roller 414. Attraction can be performed by electrostatic attraction or air suction.

[0036] Then, the conveyor belt 412 moves in a circular motion in the sub-scanning direction as the conveyor rollers 413 are rotated by the sub-scanning motor 416.

[0037] In this configured printing apparatus 500, the paper 410 is fed onto the transport belt 412 and held in place, and the paper 410 is transported in the sub-scanning direction by the circumferential movement of the transport belt 412.

[0038] Therefore, by moving the carriage 403 in the main scanning direction and driving the liquid ejection head 10 in accordance with the image signal, liquid is ejected onto the stationary paper 410 to form an image.

[0039] The liquid discharge unit 440 consists of a housing portion composed of side plates 491A, 491B and a back plate 491C, a main scanning movement mechanism 493, a carriage 403, and a liquid discharge head 10, which are components of the liquid discharge device.

[0040] In this application, the ejected liquid can be any liquid having viscosity and surface tension that allows it to be ejected from the head, and is not particularly limited to ink, 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, amino acids or proteins, calcium, or an edible material such as a natural pigment. These can be used, for example, as inkjet inks, surface treatment liquids, liquids for forming components of electronic elements and light-emitting elements or electronic circuit resist patterns, and material liquids for 3D molding.

[0041] 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.

[0042] A "liquid discharge unit" is a liquid discharge head with integrated functional components and mechanisms, and includes an assembly of parts related to liquid discharge. For example, a "liquid discharge unit" may include a combination of a liquid discharge head with at least one of the following components: a head tank, carriage, supply mechanism, maintenance and recovery mechanism, main scanning movement mechanism, and liquid circulation device.

[0043] Here, integration includes, for example, cases where the liquid dispensing head and functional components or 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 and functional components or mechanisms may be configured to be detachable from each other.

[0044] For example, some liquid dispensing units have a liquid dispensing head and head tank integrated into one unit. Others have a liquid dispensing head and head tank integrated into one unit, connected to each other by tubes or similar means. In these liquid dispensing units, a unit including a filter can also be added between the head tank and the liquid dispensing head.

[0045] Additionally, some liquid dispensing units have an integrated liquid dispensing head and carriage.

[0046] Furthermore, some liquid dispensing units integrate the liquid dispensing head and the scanning mechanism by movably holding the liquid dispensing head in a guide member that constitutes part of the scanning mechanism. Others integrate the liquid dispensing head, carriage, and main scanning mechanism.

[0047] Furthermore, some liquid dispensing units integrate the liquid dispensing head, carriage, and maintenance / recovery mechanism by fixing a cap component, which is part of the maintenance / recovery mechanism, to a carriage to which the liquid dispensing head is attached.

[0048] Furthermore, some liquid discharge units have a head tank or a liquid discharge head to which flow path components are attached, to which a tube is connected, integrating the liquid discharge head and the supply mechanism. Through this tube, the liquid from the liquid storage source is supplied to the liquid discharge head.

[0049] A "liquid dispensing device" includes devices equipped with a liquid dispensing head or liquid dispensing unit, which drive the liquid dispensing head to dispense liquid. Liquid dispensing devices include not only devices capable of dispensing liquid onto surfaces to which liquid can adhere, but also devices that dispense liquid into air or into liquid.

[0050] This "liquid dispensing device" may also include means for feeding, transporting, and dispensing paper onto materials to which liquid can adhere, as well as pre-treatment devices, post-treatment devices, etc.

[0051] For example, "liquid ejection devices" include image forming devices that eject ink to form images on paper, and three-dimensional molding devices that eject molding liquid into a powder layer formed in layers to create three-dimensional objects.

[0052] Furthermore, the term "liquid dispensing device" is not limited to those that visualize meaningful images such as letters or figures through the dispensed liquid. For example, it also includes devices that form patterns that do not have meaning in themselves, or devices that create three-dimensional images.

[0053] The term "materials to which liquid can adhere" above 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.

[0054] The materials referred to as "materials to which liquid can adhere" above include paper, thread, fibers, fabrics, leather, metal, plastic, glass, wood, ceramics, etc., as long as liquid can adhere to them, even temporarily.

[0055] Furthermore, while "liquid dispensing device" includes devices in which the liquid dispensing head and the object to which the liquid can adhere move relative to each other, it is 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.

[0056] Other examples of "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.

[0057] In this application, the terms image formation, recording, printing, copying, printing, and shaping are all considered synonymous.

[0058] Examples of the present invention are as follows: [1] The liquid discharge head 10 of the present invention comprises a plurality of nozzles for discharging liquid, a supply channel connected to the nozzles, and a supply tank connected upstream of the nozzles in the direction of liquid flow in the supply channel, wherein the inlet of the supply tank into which the liquid flows from the supply channel is located lower in the direction of gravity than the outlet from which the liquid is discharged from the supply tank toward the nozzles. With this configuration, a tank is provided in the supply channel to suppress pressure fluctuations, and since bubbles generated in the tank are discharged downstream only by the forward circulation of the liquid, pressure fluctuations caused by bubble generation are reduced, and the occurrence of printing abnormalities can be suppressed.

[0059] [2] In addition to the configuration described in [1], the liquid discharge head of the present invention comprises a recovery tank connected downstream of the nozzle in the direction of liquid flow in the supply channel, wherein the inlet into which the liquid flows from the supply channel into the recovery tank is located lower in the direction of gravity than the outlet from which the liquid is discharged downstream from the recovery tank. With this configuration, a tank is provided in the supply channel to suppress pressure fluctuations, and since bubbles generated in the tank are discharged downstream only by the forward circulation of the liquid, pressure fluctuations caused by bubble generation are reduced, and the occurrence of printing abnormalities can be suppressed.

[0060] [3] In addition to the configurations described in [1] and [2], the liquid discharge head of the present invention is characterized in that both the supply tank and the recovery tank have a damper structure for suppressing abrupt changes in pressure. With this configuration, a tank with a damper structure is provided to suppress pressure fluctuations, and since bubbles generated in the tank are discharged downstream only by the forward circulation of the liquid, pressure fluctuations caused by bubble generation are reduced, and the occurrence of printing abnormalities can be suppressed.

[0061] [4] In addition to the configurations described in any of [1] to [3], the liquid discharge head of the present invention is characterized in that it has a plurality of bends in the supply channel, and the walls of the bends have a curved cross-section. With this configuration, liquid and bubbles will not accumulate in corners and edges, thus reducing pressure fluctuations caused by bubble formation and suppressing the occurrence of printing defects.

[0062] [5] In addition to the configurations described in any of [1] to [4], the liquid discharge head 10 of the present invention is characterized in that, in the supply tank and the recovery tank, the wall surface opposite to the wall surface where the inlet and outlet are formed has a curved cross-section. With this configuration, liquid and bubbles will not accumulate in corners and edges, thus reducing pressure fluctuations caused by bubble formation and suppressing the occurrence of printing defects.

[0063] [6] In addition to the configurations described in any of [1] to [5], the liquid discharge head 10 of the present invention is characterized in that the radius of curvature of the curved portion is substantially the same as the maximum width of the supply tank or the recovery tank. With this configuration, the radius of curvature can be maximized without obstructing the flow path, so liquid and bubbles will not accumulate in corners and edges. This reduces pressure fluctuations caused by bubble generation and suppresses the occurrence of printing abnormalities.

[0064] [7] In addition to the configurations described in any of [1] to [6], the present invention is characterized in that the liquid discharge head 10 of the present invention has an inclined surface or inclined curved surface in which the wall surface approaches the outlet side as it moves upward in the direction of gravity. With this configuration, the volume of the area enclosed by the supply tank and damper structure decreases as it goes upwards, so the flow velocity of the ink Q flowing inside increases, further promoting the discharge of air bubbles.

[0065] [8] In addition to the configurations described in any of [1] to [7], the present invention is characterized in that the liquid discharge head 10 of the present invention has a damper structure in which the cross-sectional area of ​​the portion enclosed by the damper structure decreases as it moves upward in the direction of gravity. With this configuration, the volume of the area enclosed by the supply tank and damper structure decreases as it goes upwards, so the flow velocity of the ink Q flowing inside increases, further promoting the discharge of air bubbles.

[0066] [9] The present invention is characterized by being an image forming apparatus that, in addition to the configuration described in any of [1] to [8], is equipped with a liquid discharge head 10. With this configuration, pressure fluctuations can be suppressed, thereby preventing the occurrence of image abnormalities.

[0067] Although preferred embodiments of the present invention have been described above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the spirit of the invention as described in the claims, unless otherwise specifically limited in the above description. The effects described in the embodiments of the present invention are merely illustrative of the most preferred effects that may arise from the present invention, and the effects of the present invention are not limited to those described in the embodiments. [Explanation of Symbols]

[0068] 10. Liquid dispensing head 14a...nozzle 20... Supply Tank 21, 31...Inlet 22, 32...outlet 23, 24...curvature part 30... Recovery Tank 60. Flexible cover (damper structure) 61, 62...Slope surface 151...Liquid flow path (supply flow path) 151a...Bending part 500...Image forming apparatus R1, R2...radius of curvature S...Cross-sectional area Y 20 , Y 30 ...maximum width +Z...Gravity direction -Z...Upward in the direction of gravity [Prior art documents] [Patent Documents]

[0069] [Patent Document 1] Japanese Patent Publication No. 2011-148295 [Patent Document 2] Japanese Patent Publication No. 2019-151095

Claims

1. Multiple nozzles for dispensing liquid, A supply channel connected to the nozzle, In the supply channel, a supply tank is connected upstream of the nozzle in the direction of liquid flow, It has, A liquid discharge head characterized in that, in the supply tank, the inlet through which the liquid flows from the supply channel into the supply tank is located lower in the direction of gravity than the outlet through which the liquid is discharged from the supply tank toward the nozzle.

2. A liquid dispensing head according to claim 1, The supply channel includes a recovery tank connected downstream of the nozzle in the direction of liquid flow, A liquid discharge head in the recovery tank, characterized in that the inlet through which the liquid flows from the supply channel into the recovery tank is located lower in the direction of gravity than the outlet through which the liquid is discharged downstream from the recovery tank.

3. A liquid dispensing head according to claim 2, The liquid discharge head is characterized in that both the supply tank and the recovery tank have a damper structure for suppressing sudden changes in pressure.

4. A liquid dispensing head according to claim 1, The liquid discharge head is characterized in that the supply channel has a plurality of bends, and the wall surface of the bends has a curved cross-section.

5. A liquid dispensing head according to claim 2, In the supply tank and the recovery tank, A liquid discharge head characterized in that the wall surface opposite to the wall surface on which the inlet and outlet are formed has a curved cross-section.

6. A liquid dispensing head according to claim 5, A liquid discharge head characterized in that the radius of curvature of the curved portion is substantially the same as the maximum width of the supply tank or the recovery tank.

7. A liquid dispensing head according to claim 3, The damper structure is characterized by having an inclined surface or curved surface that approaches the outlet side as the wall surface moves upward in the direction of gravity.

8. A liquid dispensing head according to claim 3, The damper structure is characterized in that the cross-sectional area of ​​the portion enclosed by the damper structure decreases as it moves upward in the direction of gravity.

9. An image forming apparatus comprising a liquid dispensing head according to any one of claims 1 to 8.

Images