Liquid ejection head and image forming apparatus

Abstract

The present invention provides a liquid ejection head and an image forming apparatus, in which a tank is provided in a supply flow path to suppress pressure fluctuation, and a gas bubble generated in the tank is discharged to a downstream side only by a positive direction circulation of a liquid. The liquid ejection head of the present invention includes a plurality of nozzles that eject a liquid, a supply flow path that is connected to the nozzles, and a supply tank that is connected in the supply flow path on an upstream side of the nozzles in a flow direction of the liquid, in which the supply tank, a flow inlet of the liquid from the supply flow path into the supply tank is located in a gravitational direction at a position that is lower than a flow outlet at which the liquid is discharged from the supply tank toward the nozzle side.

Description

Technical Field

[0001] The present invention relates to a liquid jet head and an image forming apparatus including the liquid jet head. Background Technology

[0002] Image forming apparatuses that use inkjet heads to form images by ejecting liquids such as ink from nozzles are widely known.

[0003] In such inkjet heads, there are known techniques that stabilize jetting by placing a damping ink reservoir in front of the nozzle to suppress pressure fluctuations in the liquid caused by jetting. Without this damping function, the pressure fluctuations at the meniscus of the ink in the nozzle increase, the droplet volume decreases, and an image anomaly known as transition stripes is easily produced in the formed image.

[0004] However, it is known that while setting only the ink reservoir ensures a stable flow rate, air bubbles may sometimes form in the upper part or corners of the reservoir during the initial ink filling.

[0005] In addition, in a typical inkjet head, since the nozzle is located at the bottom, the ink flow direction is mostly downwards. However, since the air bubbles face upwards, they are difficult to expel naturally.

[0006] If such bubbles are not removed, they can cause image abnormalities. Therefore, techniques have been developed to easily remove the generated bubbles and to prevent the generation of bubbles (see, for example, Patent Documents 1 and 2).

[0007] However, in the existing method, the ink needs to be circulated in the opposite direction during discharge to expel air bubbles from the supply side port, which creates the problem that the initial filling takes time.

[0008] The present invention was made to solve the above-mentioned problems, and its purpose is to provide a liquid injection head in which a tank is provided in the supply flow path to suppress pressure fluctuations, and the bubbles generated in the tank are discharged downstream only through the positive circulation of the liquid.

[0009] [Patent Document 1] Japanese Patent Application Publication No. 2011-148295

[0010] [Patent Document 2] Japanese Patent Application Publication No. 2019-151095 Summary of the Invention

[0011] The liquid injection head of the present invention includes: a plurality of nozzles for injecting liquid; a supply flow path connected to the nozzles; and a supply tank connected in the supply flow path to an upstream side of the liquid flow direction, which is closer to the nozzles than to the nozzles. In the supply tank, the inlet of the liquid flowing from the supply flow path into the supply tank is located in the gravity direction at a position lower than the outlet of the liquid discharging from the supply tank toward the nozzles.

[0012] According to the present invention, a tank can be provided in the supply flow path to suppress pressure fluctuations, while the bubbles generated in the tank are discharged downstream only in the positive direction of the liquid. Attached Figure Description

[0013] Figure 1 The diagram shown is an example of the configuration of the liquid injection head of the present invention.

[0014] Figure 2 (a)-(b) are Figure 1 This is an example diagram of the nozzle configuration of the liquid injection head shown.

[0015] Figure 3 yes Figure 1 An enlarged view of the flow path structure of the liquid jet head shown.

[0016] Figure 4 (a)-(b) are Figure 3 The diagram shows the generation and movement of bubbles in the liquid jet module.

[0017] Figure 5 Figures (a)-(e) show existing examples of liquid injection heads.

[0018] Figure 6 Figures (a)-(c) show an example of the state of bubble discharge in the liquid jet head of the present invention.

[0019] Figure 7 The diagram shown is an example of the structure of the damper of the present invention.

[0020] Figure 8 The diagram shown is an example of the effect of the structure of the present invention in suppressing pressure fluctuations.

[0021] Figure 9 The diagram shown is an example of the configuration of the curved portion in the flow path of the present invention.

[0022] Figure 10 (a)-(b) are Figure 9 An example diagram illustrating the effect of curvature.

[0023] Figure 11The diagram shown is an example of the configuration of the common flow path components of a liquid injection head.

[0024] Figure 12 The diagram shows the positional relationship between the independent flow path of the liquid jet head and the nozzle orifice.

[0025] Figure 13 Viewed from the Z-direction side Figure 12 The diagram shown illustrates the configuration.

[0026] Figure 14 The diagram shown is an example of the configuration of the liquid injection device of the present invention.

[0027] Figure 15 The diagram shown is an example of the configuration of the liquid injection unit of the present invention. Detailed Implementation

[0028] Figure 1 As a first embodiment of the present invention, a liquid jet head 10, which is an inkjet head, will be described.

[0029] In the following explanation, the nozzle arrangement direction (the direction of the long side of the liquid jet head) will be defined as the Y direction, the direction of liquid ejection from the nozzle (the direction of the height of the liquid jet head) will be defined as the Z direction, and the direction orthogonal to both the X and Z directions (the direction of the short side of the liquid jet head) will be defined as the X direction.

[0030] The liquid ejector head 10 includes a nozzle plate 14, a flow path component 15, and a cover 11 serving as a housing component. A supply port 12 for supplying ink Q (as a liquid) is provided at one end of the flow path component 15 in the X direction, and a discharge port 13 for discharging the ink Q is provided at the other end of the flow path component 15 in the Y direction. Furthermore, a connector 16 for communicating with the actuator 2 housed within the cover is provided on the upper part of the cover 11.

[0031] The nozzle plate 14, flow path component 15, and cover 11 are made of metal, resin, or ceramic. The cover 11 internally houses and supports the liquid injection module 1 (described later). Figure 3 The flow path component 15 defines the flow path through which the liquid flows, and the nozzle plate 14 has a plurality of nozzles for spraying liquids such as recording fluid. The nozzle plate 14 is mechanically fixed to the flow path component 15, and the cover 11 is mechanically (removably) fixed to the base 17 that holds the flow path component 15 and the nozzle plate 14.

[0032] Figure 2 This is a diagram illustrating an example of the arrangement of nozzles on nozzle plate 14.

[0033] like Figure 2As shown in (a), a nozzle array can be set in the center of the nozzle plate in the X direction (short side direction of the nozzle head), or as... Figure 2 As shown in (b), the nozzles 14a can be configured in a staggered pattern, with two rows of nozzles arranged in the X direction. Additionally, Figure 2 The nozzle arrangement shown is an example. For example, it can also be configured in an alternating manner, with two sets of two columns of nozzles in the X direction, resulting in a total of four columns of nozzles, or it can be configured with multiple nozzle columns in which the positions of the nozzles in the X direction (short side direction of the nozzle head) are the same.

[0034] In this embodiment, ink Q is discharged from each nozzle 14a via the liquid jet module 1, thereby causing the ink Q, which is a recording liquid, to accumulate on the recording medium (e.g., paper) based on image data from the control unit, thereby forming an image.

[0035] In this embodiment, the description of the internal structure and configuration of each part of the liquid jet module 1 is omitted, but the structure of a general inkjet head can also be used.

[0036] Figure 3 The diagram shown is a cross-sectional view of the internal structure of the flow path component 15 and the liquid injection module 1.

[0037] From the supply port 12 to the discharge port 13, a liquid flow path 151 is formed through the flow path component 15 as a supply flow path.

[0038] Midway along the liquid flow path 151, along the flow direction of the ink Q, are respectively provided a supply tank 20, a nozzle orifice 153 forming an opening at a position abutting against the nozzle plate 14, a first liquid chamber 154 including the nozzle orifice 153, and a recovery tank 30, from which... Figure 3 The liquid flow path 151, which extends from the downstream side of the liquid flow path, is connected to the discharge port 13.

[0039] The nozzle orifice 153 is an opening on the bottom surface of the first liquid chamber 154, positioned so that it aligns with the nozzle 14a when the nozzle plate 14 is installed. This nozzle orifice 153... Figure 3 The text omits certain details, but it can be understood as follows: Figure 2 As illustrated, a plurality of nozzle holes 153 are formed along the Y direction. Furthermore, in the case of having a plurality of nozzle holes 153, it is preferable to have a configuration in which droplets are discharged from the nozzle holes 153 at opposite positions by the operation of actuators 2 arranged along the Y direction described later.

[0040] In addition, an ink cartridge or the like is connected to the front end of the discharge port 13, forming a loop that allows ink Q to circulate from the supply side to the recycling side.

[0041] At the top of the first liquid chamber 154, on the side opposite to the nozzle orifice 153, an actuator 2 such as a piezoelectric element is arranged. By the action of the actuator 2, the volume of the first liquid chamber 154 changes, and ink Q is discharged as droplets from the nozzle orifice 153 opposite to the actuator 2.

[0042] Furthermore, although the actuator 2 is described here as a piezoelectric element, it is not limited to any configuration that functions as a drive source for discharging ink Q from the nozzle orifice 153.

[0043] In addition, the actuator 2 contracts and expands by an electrical signal communicated via connector 16, thereby causing a change in the volume of the first liquid chamber 154, which can be transmitted from the control unit of the image forming apparatus body.

[0044] like Figure 3 As shown, 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 liquid flow path 151 and the side from the supply tank 20 toward the nozzle orifice 153.

[0045] In addition, the supply tank 20 has a curved portion 23 provided on the wall opposite to the inlet 21 and a curved portion 24 provided on the wall opposite to the outlet 22.

[0046] Both curvature sections 23 and 24 form curved walls with a curvature radius of R1. The curvature radius R1 can be determined by any value, but it is most preferably set to be approximately the same as the widths Y20 and Y30 in the Y direction of the supply tank 20 and the recovery tank 30, respectively.

[0047] That is, the preferred setting is R1≈Y20≈Y30.

[0048] With this configuration, the corners and angular portions in the supply tank 20 and the recovery tank 30 that are the cause of air bubbles can have a large curvature within a range that does not impede the flow of ink Q, thus improving the air bubble discharge performance in the supply tank 20 and the recovery tank 30.

[0049] In addition, 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.

[0050] Based on this composition, and Figure 4 Compared to the existing configuration shown, it is less likely to generate bubbles p, and the generated bubbles p are easily discharged along the flow of ink Q towards the outlet 22 side, that is, in the positive direction of flow.

[0051] Similarly, in the recovery tank 30, the inlet 31 connected from the nozzle orifice 153 side is also positioned lower than the outlet 32 ​​that flows to the discharge port 13.

[0052] This point will be explained in detail.

[0053] First of all, Figure 5 In this example, as a comparison with existing ink tanks, a case is illustrated in which a supply-side ink tank 40 and a recovery-side ink tank 50 are provided in the liquid flow path 151.

[0054] At this time, the liquid jet module 1 is usually very narrow, and the liquid flow path 151 is difficult to handle. Therefore, the inlet 41 of the supply-side ink tank 40 is located above the supply-side ink tank 40.

[0055] In this case, such as Figure 5 As shown in (b) and (c), when ink Q is filled from an empty state, air is trapped at the top, and bubbles p are easily generated regardless.

[0056] Furthermore, if the ink tank 40 on the supply side is connected to the straight liquid flow path 151 in this way, the bubbles p generated in the liquid flow path 151 will naturally be retained on the inlet 41 side due to buoyancy.

[0057] If such bubbles p merge and grow larger, then in extreme cases, such as Figure 5 As shown in (d) and (e), the upper part of the ink tank 40 on the supply side is occupied by air bubbles p. Due to the reduced flow rate of ink Q, it is difficult to apply sufficient pressure, which will result in insufficient pressure in the nozzle orifice 153 or poor image formation.

[0058] Thus, even though the method of removing air bubbles p by reverse circulation of ink Q was used when air was trapped in the upper part, the repeated reverse and forward circulation also led to an increase in the initial filling time.

[0059] On the other hand, according to the configuration of this embodiment, such as Figure 3 As already shown, the inlet 21 is positioned below the outlet 22.

[0060] Therefore, as Figure 6 (a) to Figure 6 As shown in (c), even if bubbles p are generated when filling the supply tank 20, bubbles p are easily expelled from the outlet 22 and flow easily.

[0061] Similarly, in the recovery tank 30, the inlet 31, which is on the upstream side, is also positioned lower than the outlet 32, thus making it easier for the generated bubbles p to be discharged in the positive direction towards the discharge port 13.

[0062] In other words, in the supply tank 20 and the recovery tank 30, the outlets 22 and 32 are respectively set so that they open at the top of the supply tank 20 and the recovery tank 30.

[0063] Based on this configuration, the structure becomes such that air is not easily trapped when filling ink Q, and air bubbles p are not easily left behind. Even when air bubbles p are generated, the air bubbles p can be easily expelled through the positive circulation of ink Q.

[0064] According to this configuration, a tank can be installed in the supply flow path to suppress pressure fluctuations, while the bubbles generated in the tank are discharged downstream only in the positive direction of the liquid.

[0065] In addition, such as Figure 7 As shown, flexible covers 60 are provided in both the supply tank 20 and the recovery tank 30. Each flexible cover 60 has a damping structure with a trapezoidal cross-sectional area when viewed from the side. Furthermore, since the configuration of the flexible covers 60 is substantially the same in both the supply tank 20 and the recovery tank 30, in this embodiment, only the flexible cover 60 installed on the supply tank 20 will be described.

[0066] like Figure 7 As shown, the flexible cover 60 is configured such that the supply tank 20 has a trapezoidal cross-section when viewed from the side.

[0067] That is, the flexible cover 60 in this embodiment has an inclined surface 61 that approaches the outlet 22 side as the wall moves upward in the direction of gravity.

[0068] In addition, in this embodiment, in order to make the shape of the supply tank 20 symmetrical, it also has an inclined surface 62 on the opposite side, similar to the side of the inlet 21.

[0069] According to this flexible cover 60, even if a large amount of ink Q flows into the supply tank 20, the flexible cover 60 can still maintain its position. Figure 7 As shown, the deformation in the ±X direction allows the supply tank 20 as a whole to suppress the flow rate of ink Q, thereby suppressing rapid pressure fluctuations.

[0070] Furthermore, if the wall of the flexible cover 60 forms an inclined surface 61 and approaches the outlet 22 side upwards, the cross-sectional area S of the portion surrounded by the flexible cover 60 and the supply tank 20 (represented by the diagonal line in the figure) decreases as it moves towards the outlet 22. This means that the volume of the portion surrounded by the supply tank 20 and the flexible cover 60 decreases as it moves upwards. Based on this shape, the ink Q flowing inside increases in velocity as it moves towards the outlet 22, further promoting the removal of air bubbles.

[0071] In this way, the flexible cover 60, which serves as the damping structure of the supply tank 20, increases the bubble discharge effect by becoming a trapezoidal shape in which the upper cross section decreases as it moves upward in the direction of gravity.

[0072] Regarding the presence or absence of damping effect of the flexible cover 60, the horizontal axis is set to time and the vertical axis to pressure. Figure 8 In the diagram, dashed lines represent the case of an undamped structure, and solid lines represent the case of a damped structure.

[0073] Additionally, when pressure variations exceed 2460 Pa, streaks may occur during printing. Figure 8 In this context, the threshold for this pressure variation is also represented by a dashed line.

[0074] from Figure 8 It is known that without a damper, there is a risk of stripe formation due to pressure fluctuations exceeding 2460 Pa. However, with the flexible cover 60 installed as a damping structure, the pressure fluctuations are always suppressed to less than 2460 Pa, thus suppressing stripe formation throughout the entire processing time.

[0075] like Figure 9 As shown, the bubbles p discharged by the effect of the flexible cover 60 and the supply tank 20 move through the first liquid chamber 154 to the recovery tank 30.

[0076] As described above, in the recovery tank 30, the inlet 31, which is the upstream side of the liquid flow path 151, is located at the bottom, and the outlet 32 ​​is located at the top. Therefore, it is also easy to discharge the bubbles p in the recovery tank 30 and discharge them to the discharge port 13 side.

[0077] Additionally, in the corners and other parts that form such a liquid flow path 151, such as Figure 9 As shown, curved portions 151a are formed at each corner. Furthermore, the walls of these curved portions 151a are formed as curved surfaces with a cross-section having a radius of curvature R2.

[0078] With this configuration, the movement of bubbles is not hindered by corners or angles when passing through the liquid flow path 151, and the bubble discharge performance is improved.

[0079] In addition, such as Figure 10 As shown, the above-mentioned components are effective not only during the initial filling of ink Q, but also during the ink flushing process after ink Q is discharged.

[0080] Specifically, when air flows in from the supply port 12 to discharge ink Q, in the existing example, such as Figure 10As shown in (a) as a comparative example, there is a possibility that ink Q remains in the corners or angular portions.

[0081] However, in this embodiment, where curved surfaces with a radius of curvature R1 are formed in the curved portions 23 and 24 at the corners of the supply tank 20, as... Figure 10 As shown in (b), because the ink Q is easily concentrated towards the inlet 21 or outlet 22 by the curvature sections 23 and 24, it will not stagnate at corners or angular portions. Furthermore, because the lateral airflow flowing in from the inlet 21 bends directly along the curvature of the curvature section 23 to become an upward airflow, it is more efficient than airflow from corners that only have right angles. Figure 10 Compared to the comparative example (a), it can be considered that the excretion of ink Q is also improved.

[0082] This effect also applies to the wall surface of the curved portion 151a of the fluid flow path 151, which has curvature, so the description is omitted.

[0083] Furthermore, in the above embodiments, for the purpose of simplification, the description of the structure of the liquid jet module 1 is described as jetting ink Q from the nozzle hole 153 opening in the first liquid chamber 154, but it is not limited to this configuration.

[0084] Figure 11 A specific configuration example of the flow path component 15 of the liquid injection module 1 is also shown.

[0085] The flow path component 15 has an upper structure 155 having a first liquid chamber 154 inside, and a common flow path component 156 located on the bottom surface of the upper structure 155. The groove 157 formed in the common flow path component 156 constitutes a flow path for ink Q connecting the two upper structures 155.

[0086] On the bottom side of the common flow path component 156, a nozzle hole 153 is provided as an opening, and a second liquid chamber 158 is connected from the nozzle hole 153 downward.

[0087] Figure 12 This is a perspective view schematically showing the configuration of the common flow path component 156 and its positional relationship with the second liquid chamber 158. A vibrating plate 160 and an independent flow path component 170 are provided on the Z-direction side of the common flow path component 156. On the vibrating plate 160, piezoelectric elements 161 are arranged in a positional relationship corresponding to the second liquid chamber 158.

[0088] The second liquid chamber 158 is a smaller liquid chamber that functions as a reservoir for ink Q, and a piezoelectric element 161 is provided at each corresponding position of the second liquid chamber 158.

[0089] According to this structure, when the piezoelectric element 161 at the corresponding position contracts and expands, the volume of the second liquid chamber 158 contracts and expands, and ink Q is discharged from the nozzle 14a at the opening of the second liquid chamber 158.

[0090] like Figure 12 As shown, starting from the first liquid chamber 154, grooves 157 formed in the common flow path component 156 as branches extend differently from each other, and form the flow path of each nozzle 14a in the form of connecting with these different grooves 157.

[0091] Therefore, for example, when viewing the liquid injection module 1 from the Z-side plane... Figure 13 In the diagram, starting from the first liquid chamber 154 on the left, ink Q flows toward the opposite side of the first liquid chamber 154 via a channel 157 that serves as a branch, forming a shape with a nozzle 14a opening midway through the flow path. Figure 13 In the image, such a flow path is schematically illustrated with arrows.

[0092] In addition, there are various other configurations of the liquid injection head 10 besides those listed here.

[0093] Such a liquid injection head 10 is used in various liquid injection devices, such as Figure 14 The printing apparatus 500 shown is an example of an image forming apparatus. (See reference...) Figure 14 as well as Figure 15 An example of a printing apparatus will be given. Figure 14 The image shown is a side view illustrating the main parts of the device. Figure 15 The diagram shown is a top view illustrating the main components of the device.

[0094] The printing apparatus 500 is a serial type device, which, through... Figure 15 The main scanning movement mechanism 493 shown has a carriage 403 that reciprocates in the main scanning direction. The main scanning movement mechanism 493 includes a guide member 401, a main scanning motor 405, and a timing belt 408. The guide member 401 is mounted on the left and right side plates 491A and 491B, holding the carriage 403 in a movable position. Then, via the main scanning motor 405 and the timing belt 408 mounted between the drive pulley 406 and the driven pulley 407, the carriage 403 reciprocates in the main scanning direction.

[0095] The carriage 403 houses a liquid jetting unit 440, which includes a liquid jetting head 10 according to the present invention and an ink reservoir 205 for supplying ink to the liquid jetting head 10. The liquid jetting head 10 of the liquid jetting unit 440 jets liquids of various colors—yellow (Y), cyan (C), magenta (M), and black (K)—as ink Q, depending on the connected ink reservoir 205. Furthermore, the liquid jetting head 10 is also mounted with a nozzle array consisting of multiple nozzles arranged in a sub-scanning direction orthogonal to the main scanning direction, and with the jetting direction facing downwards.

[0096] The liquid ejector head 10 is connected to the ink tank 205, and as described above, the desired color of liquid is circulated and supplied as ink Q.

[0097] The printing apparatus 500 includes a conveying mechanism for conveying paper 410, which serves as a recording medium. The conveying mechanism includes a conveyor belt 412 as a conveying means and a secondary scanning motor 416 for driving the conveyor belt 412.

[0098] The conveyor belt 412 adsorbs and transports the paper 410 to a position opposite to the liquid jet head 10. The conveyor belt 412 is a loop belt, positioned between the conveyor roller 413 and the tension roller 414. Adsorption can be achieved through electrostatic adsorption or air attraction, etc.

[0099] Then, the conveyor belt 412 moves around in the secondary scanning direction by rotating the conveyor roller 413 through the secondary scanning motor 416.

[0100] In this printing apparatus 500, paper 410 is fed and attracted on conveyor belt 412, and the paper 410 is transported in the sub-scanning direction by the circular movement of conveyor belt 412.

[0101] Therefore, by moving the carriage 403 in the main scanning direction while driving the liquid jet head 10 according to the image signal, liquid is sprayed onto the stopped paper 410 to form an image.

[0102] The liquid injection unit 440, among the components constituting the liquid injection device, is composed of a frame consisting of side plates 491A, 491B and a back plate 491C, a main scanning moving mechanism 493, a carriage 403 and a spray head 10.

[0103] In this application, the liquid to be sprayed is any liquid with viscosity and surface tension suitable for ejection from the printhead, and is not particularly limited to ink. Preferably, it is a liquid with a viscosity of 30 MPa·s or less at room temperature and pressure, or when heated or cooled. More specifically, it includes solutions, suspensions, latexes, etc., of solvents such as water or organic solvents, colorants such as dyes and pigments, functional materials such as polymeric compounds, resins, and interfacial activators, biocompatible materials such as DNA, amino acids and proteins, and calcium, and edible materials such as natural pigments. These liquids can be used for applications such as inkjet inks, surface treatment liquids, liquids for forming resist layers in electronic components and light-emitting elements, and liquids for three-dimensional modeling.

[0104] Energy sources for jetting liquids include thermal actuators that use electrothermal conversion elements such as actuators (layered piezoelectric elements and thin-film piezoelectric elements) and heating resistors, and electrostatic actuators that consist of a vibrating plate and opposing electrodes.

[0105] A "liquid spraying unit" is an assembly of parts related to liquid spraying, formed by integrating functional components and mechanisms into a liquid spraying head. For example, a "liquid spraying unit" may include at least one of the following components combined with a liquid spraying head: a nozzle tank, a carriage, a supply mechanism, a maintenance and recovery mechanism, a main scanning movement mechanism, and a liquid circulation device.

[0106] Here, integration refers to the mutual fixation of, for example, liquid injection heads and functional parts / mechanisms through fastening, bonding, or locking, whereby one is kept movable relative to the other. Alternatively, liquid injection heads and functional parts / mechanisms can also be designed to be detachable from each other.

[0107] For example, some liquid injection units integrate the liquid injection head and the nozzle tank. Others integrate the liquid injection head and nozzle tank by connecting them via hoses or the like. Alternatively, a unit containing a filter can be added between the nozzle tank and the liquid injection head in these liquid injection units.

[0108] In addition, as a liquid injection unit, there is a device that integrates the liquid injection head and the carriage.

[0109] Additionally, as a liquid jetting unit, some designs integrate the liquid jetting head with a guide member that is part of the scanning movement mechanism, thereby making the liquid jetting head and the scanning movement mechanism integrated. Other designs integrate the liquid jetting head, carriage, and main scanning movement mechanism.

[0110] In addition, as a liquid injection unit, a cover component, which is part of the maintenance and recovery mechanism, is fixed on the carriage on which the liquid injection head is installed, so that the liquid injection head, the carriage, and the maintenance and recovery mechanism are integrated into one.

[0111] Additionally, as a liquid injection unit, a hose is connected to the liquid injection head, which is equipped with a nozzle canister or flow path components, to integrate the liquid injection head and the supply mechanism. Liquid from the liquid storage source is supplied to the liquid injection head through this hose.

[0112] The "liquid jetting device" includes a spray head and a spraying unit, and includes a device for driving the spray head to spray liquid. The liquid jetting device is not only a device capable of spraying liquid relative to an object to which the liquid can adhere, but may also include a device for spraying liquid into the air or into a liquid.

[0113] The "liquid jetting device" may also include mechanisms for feeding, conveying, and discharging liquid-adherent materials, as well as other pre-processing and post-processing devices.

[0114] For example, as a "liquid jetting device", there is an image forming device that jets ink to form an image on paper, and a three-dimensional modeling device that jets a modeling liquid into a powder layer in which powder is formed in layers in order to shape a three-dimensional object.

[0115] Furthermore, "liquid jetting devices" are not limited to visualizing interesting images such as text and graphics by jetting liquid. For example, they also include things that form graphics that are not inherently meaningful, as well as things that shape three-dimensional images.

[0116] The term "substances to which liquids can adhere" refers to substances to which liquids can adhere at least temporarily, meaning substances that stick or permeate after adhesion. Specific examples include the recording medium such as paper, recording paper, film, and cloth; electronic components such as electronic substrates and piezoelectric elements; and media such as powder layers, organ models, and inspection parts. Unless otherwise specified, this includes all substances to which liquids can adhere.

[0117] The aforementioned "substances that can adhere to liquids" can be any material such as paper, silk, fiber, cloth, leather, metal, plastic, glass, wood, ceramics, etc., to which liquids can adhere even temporarily.

[0118] In addition, a "liquid jetting device" includes a device in which a liquid jetting head and a liquid-adherable object move relative to each other, but is not limited to this. Specific examples include serial devices that move the liquid jetting head and linear devices that do not move the liquid jetting head.

[0119] In addition, as "liquid spraying devices", there are also treatment liquid coating devices that spray treatment liquid onto paper for purposes such as paper surface modification, and spray granulation devices that spray a component liquid in which raw materials are dispersed in a solution through a nozzle to granulate the small particles of the raw materials.

[0120] In addition, in the terminology used in this application, image formation, recording, printing, writing, printing, and modeling are all synonyms.

[0121] The present invention can be described, for example, as follows. [1]

[0123] The liquid injection head 10 of the present invention includes: a plurality of nozzles for injecting liquid; a supply flow path connected to the nozzles; and a supply tank connected in the supply flow path to an upstream side of the liquid flow direction, which is closer to the nozzles than to the nozzles. In the supply tank, the inlet of the liquid flowing from the supply flow path into the supply tank is located in the gravity direction at a position lower than the outlet of the liquid discharging from the supply tank toward the nozzles.

[0124] According to this configuration, a tank can be installed in the supply flow path to suppress pressure fluctuations, while the bubbles generated in the tank are discharged downstream only in the positive direction of the liquid. Therefore, the pressure fluctuations caused by the generation of bubbles are reduced, thereby suppressing the generation of printing abnormalities. [2]

[0126] In addition to the configuration described in [1], the liquid jet head of the present invention has a recovery tank connected in the supply flow path to the downstream side of the liquid flow direction, which is closer to the nozzle than the nozzle. In the recovery tank, the inlet of the liquid flowing from the supply flow path into the recovery tank is located in the gravity direction at a position lower than the outlet of the liquid being discharged from the recovery tank toward the downstream side.

[0127] According to this configuration, a tank can be installed in the supply flow path to suppress pressure fluctuations, while the bubbles generated in the tank are discharged downstream only in the positive direction of the liquid. Therefore, the pressure fluctuations caused by the generation of bubbles are reduced, thereby suppressing the generation of printing abnormalities. [3]

[0129] In addition to the configurations described in [1] and [2], the liquid injection head of the present invention includes: both the supply tank and the recovery tank have damping structures for suppressing abrupt changes in pressure.

[0130] According to this configuration, while suppressing pressure fluctuations by setting a tank with a damping structure, the bubbles generated in the tank are discharged downstream only by circulating in the positive direction of the liquid. Therefore, the pressure fluctuations caused by the generation of bubbles are reduced, thereby suppressing the generation of printing abnormalities. [4]

[0132] In addition to any one of the configurations in [1] to [3], in the liquid injection head of the present invention, the supply flow path has a plurality of bends, and the cross-section of the wall of the bend has curvature.

[0133] According to this configuration, since liquid or bubbles will not stagnate in corners or edges, pressure fluctuations caused by bubble formation can be reduced, thereby suppressing printing abnormalities. [5]

[0135] In addition to any one of the configurations in [1] to [4], in the liquid injection head 10 of the present invention, a curved portion is formed in the cross section of the wall surface opposite to the wall surface on which the inlet and outlet are formed in the supply tank and the recovery tank.

[0136] According to this configuration, since liquid or bubbles will not stagnate in corners or edges, pressure fluctuations caused by bubble formation can be reduced, thereby suppressing printing abnormalities. [6]

[0138] Apart from any one of the configurations in [1] to [5], in the liquid injection head 10 of the present invention, the radius of curvature of the curved portion is the same as the maximum width in the supply tank or the recovery tank.

[0139] According to this configuration, since the radius of curvature can be maximized without obstructing the flow path, liquid or bubbles will not stagnate in corners or edges. Therefore, pressure fluctuations caused by bubble generation can be reduced, thereby suppressing printing abnormalities. [7]

[0141] In addition to the configuration described in any one of [1] to [6], in the liquid jet head 10 of the present invention, the damping structure has an inclined surface or inclined curved surface whose wall surface approaches the outlet side as it moves upward in the direction of gravity.

[0142] If this configuration is adopted, since the volume of the part surrounded by the supply tank and the damping structure decreases as it tends upward, the flow rate of the ink Q flowing inside becomes faster, thereby further promoting the removal of bubbles. [8]

[0144] Apart from the configuration described in any one of [1] to [7], in the liquid jet head 10 of the present invention, the cross-sectional area of ​​the portion of the damping structure surrounded by the damping structure decreases as it moves upward in the direction of gravity.

[0145] If this configuration is adopted, since the volume of the part surrounded by the supply tank and the damping structure decreases as it tends upward, the flow rate of the ink Q flowing inside becomes faster, thereby further promoting the removal of bubbles. [9]

[0147] The present invention is characterized in that, in addition to the configuration described in any one of [1] to [8], it also includes an image forming apparatus for a liquid jet head 10.

[0148] Based on this structure, pressure variations can be suppressed, thereby suppressing the generation of image anomalies.

[0149] While the preferred embodiments of the present invention have been described above, the present invention is not limited to the specific embodiments described above. Various modifications and alterations can be made within the scope of the concept of the present invention as described in the scope of the claims, unless otherwise specified in the above description.

[0150] The effects described in the embodiments of this invention are merely examples of the best effects produced by this invention, and the effects of this invention are not limited to those described in the embodiments of this invention.

Claims

1. A liquid injection head, characterized in that... include: Multiple nozzles that spray liquid; A supply flow path, which is connected to the nozzle, and A supply tank, in the supply flow path, is connected upstream of the nozzle in the direction of liquid flow. In the supply tank, the inlet where the liquid flows into the supply tank from the supply flow path is located in the direction of gravity below the outlet where the liquid is discharged from the supply tank toward the nozzle side.

2. The liquid injection head according to claim 1, characterized in that: The supply path includes a recovery tank connected downstream of the nozzle in the direction of liquid flow. In the recovery tank, the inlet where the liquid flows into the recovery tank from the supply path is located in the direction of gravity below the outlet where the liquid is discharged from the recovery tank towards the downstream side.

3. The liquid injection head according to claim 2, characterized in that... include: Both the supply tank and the recovery tank have damping structures to suppress abrupt changes in pressure.

4. The liquid injection head according to claim 1, characterized in that: The supply flow path has multiple bends, and the cross-section of the wall of each bend has curvature.

5. The liquid injection head according to claim 2, characterized in that: In the supply tank and the recovery tank, A curved portion is formed in the cross section of the wall surface that is opposite to the wall surface on which the inlet and outlet are formed.

6. The liquid injection head according to claim 5, characterized in that: The radius of curvature of the curved portion is the same as the maximum width in the supply tank or the recovery tank.

7. The liquid injection head according to claim 3, characterized in that: The damping structure has an inclined surface or inclined curved surface whose wall approaches the outlet side as it moves upward in the direction of gravity.

8. The liquid injection head according to claim 3, characterized in that: The cross-sectional area of ​​the portion of the damping structure surrounded by the damping structure decreases as it moves upward in the direction of gravity.

9. An image forming apparatus, characterized in that: The liquid injection head is provided with any one of claims 1 to 8.

Images