Liquid ejection apparatus and liquid ejection method

Abstract

To stably supply pseudoplastic liquid to a circulation supply flow path formed in a flow path member.SOLUTION: A liquid ejection apparatus has a flow path member having a flow path through which a pseudoplastic liquid flows, an actuator that applies a pressure to the liquid inside the flow path to cause a liquid droplet to be ejected from the flow path member, and a flow rate setting unit that sets a flow rate of the liquid inside the flow path. The flow rate setting unit adjusts a circulation flow rate of the liquid, which circulates through a supply reservoir, a plurality of supply manifolds, a plurality of supply flow paths, a plurality of pressure chambers, a plurality of collection flow paths, a plurality of collection manifolds, and a collection reservoir in this order, to a predetermined target flow rate. The flow path has a flow path shape with which average viscosity of the liquid in the supply flow paths becomes half or less of average viscosity of the liquid in the supply manifolds when the circulation flow rate is the target flow rate.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to a liquid ejection apparatus and a liquid ejection method. [Background technology]

[0002] BACKGROUND ART Liquid ejection devices such as inkjet printers are known. Patent Document 1 discloses an inkjet recording device that uses thixotropic ink. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-216425 Summary of the Invention

[0004] A liquid ejection device according to one aspect of the present disclosure includes a flow path member, an actuator, and a flow rate setting unit. The flow path member has a flow path through which a pseudoplastic liquid flows. The actuator applies pressure to the liquid in the flow path to eject droplets from the flow path member. The flow rate setting unit sets the flow rate of the liquid in the flow path. The flow path includes a supply reservoir, multiple supply manifolds, multiple supply flow paths, multiple pressure chambers, multiple nozzles, multiple recovery flow paths, and a recovery reservoir. The liquid is supplied to the supply reservoir. The multiple supply manifolds are connected to the supply reservoir and receive the liquid from the supply reservoir. Two or more of the multiple supply flow paths are provided for each of the multiple supply manifolds, and each is connected to one of the multiple supply manifolds and receives the liquid from the connected supply manifold. The multiple pressure chambers are separately connected to the multiple supply flow paths, receive the liquid from the multiple supply flow paths, and apply pressure to them by the actuator. The multiple nozzles are connected to the multiple pressure chambers separately from one another and eject the liquid from the pressure chambers to the outside. The multiple recovery flow paths are connected to the multiple pressure chambers separately from one another and recover the liquid from the multiple pressure chambers. The multiple recovery manifolds are each connected to two or more of the multiple recovery flow paths and recover the liquid from the multiple recovery flow paths. The recovery reservoir is connected to the multiple recovery manifolds and recovers the liquid from the multiple recovery manifolds. The flow rate setting unit adjusts the circulation flow rate of the liquid circulating sequentially through the supply reservoir, the multiple supply manifolds, the multiple supply flow paths, the multiple pressure chambers, the multiple recovery flow paths, the multiple recovery manifolds, and the recovery reservoir to a predetermined target flow rate. The flow paths have a flow path shape such that when the circulation flow rate is the target flow rate, the average viscosity of the liquid in the supply flow paths is less than half the average viscosity of the liquid in the supply manifold.

[0005] A liquid ejection method according to one aspect of the present disclosure is a liquid ejection method using the liquid ejection device, wherein the liquid has a shear rate of 1000 s -1 The viscosity is 0.02 Pa s or more and 0.4 Pa s or less when the shear rate is 0.01 s -1 A pseudoplastic fluid with a viscosity of 0.5 Pa·s or more and 50 Pa·s or less is used. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a schematic diagram illustrating an overall configuration of a liquid ejection device according to an embodiment. [Figure 2] FIG. 2(a) is an exploded perspective view of a head of a liquid ejection device according to an embodiment, and FIG. 2(b) is a perspective view of a second flow path member included in the head. [Figure 3] 3(a) and 3(b) are planar perspective views of the head according to the embodiment. [Figure 4] FIG. 3(b) is an enlarged view of region IV in FIG. [Figure 5] FIG. 2 is a perspective view of an individual flow path of a head according to an embodiment. [Figure 6] 6(a) is a cross-sectional view taken along line VIa-VIa in FIG. 5, and FIG. 6(b) is a cross-sectional view taken along line VIb-VIb in FIG. [Figure 7] 5A and 5B are diagrams showing the characteristics of a liquid used in the liquid ejection device according to the embodiment. [Figure 8] FIG. 10 is a diagram showing an example of an average viscosity for each portion of a flow path according to the embodiment. [Figure 9] FIG. 10 is a schematic cross-sectional view of an individual flow path according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the drawings are schematic. Therefore, details may be omitted. Furthermore, the dimensional ratios do not necessarily correspond to the actual ratios. The dimensional ratios between the drawings do not necessarily correspond to the actual ratios. Certain dimensions may be shown larger than they actually are, and certain shapes may be exaggerated.

[0008] The drawings may include arrows indicating the D1 to D6 directions. These directions are parallel to the ejection surface 3a, which will be described later. The D2 and D5 directions are, for example, parallel to the longitudinal direction of the head 3, which will be described later, and from another perspective, are so-called main scanning directions. The D3 and D6 directions are directions orthogonal to the D2 and D5 directions. The D1 and D4 directions are directions inclined with respect to the D3 and D6 directions.

[0009] (Overall configuration of liquid ejection device) FIG. 1 is a diagram schematically illustrating the configuration of a main part of a liquid ejection device 1 (hereinafter, sometimes referred to as "ejection device 1") according to an embodiment.

[0010] The ejection device 1 is configured as a device that deposits liquid on the surface of the target object 101 by ejecting droplets from the ejection surface 3a of the head 3 toward the target object 101, like an inkjet printer. Note that the ejection surface 3a may face in any direction relative to the vertical direction, but in the following description, for convenience, the direction facing the ejection surface 3a will be considered downward, and terms such as upper surface and lower surface will be used.

[0011] The specific type (application) of the ejection device 1 may be any appropriate one. For example, the ejection device 1 may be a device that prints characters and figures (or, from another perspective, records information) by applying ink to a recording medium (e.g., paper) serving as the object 101. That is, the ejection device 1 may be what is commonly referred to as a printer. Also, for example, the ejection device 1 may be a device that applies paint to the body of an automobile serving as the object 101 to decorate the body. Also, for example, the ejection device 1 may be a device that applies a liquid containing conductive particles to a circuit board serving as the object 101 to form wiring.

[0012] Also, unlike the illustrated example, the discharging device 1 does not have to be a device that applies a liquid to the target object 101. For example, the discharging device 1 may be a device that discharges a liquid chemical into a container that reacts with a substance in the container, or a device that sprays a disinfectant into the atmosphere.

[0013] As can be understood from the examples of specific types of the ejection device 1 described above, the material, shape, and dimensions of the target object 101 may be any appropriate one. Since FIG. 1 is a schematic diagram, the target object 101 is shown as a rectangular parallelepiped. Examples of materials for the target object 101 include paper, cloth, resin, metal, ceramic, and wood, as well as combinations thereof. Examples of types of the target object 101 include recording media (e.g., roll paper or sheet paper), circuit boards, clothing, beverage containers, storage containers, electronic device housings, and automobile bodies. The target object 101 or the area thereon onto which the liquid is applied may be narrower or wider than the ejection surface 3a from which droplets are ejected.

[0014] Furthermore, as can be understood from the examples of specific types of the discharge device 1 described above, the type of liquid may also be any appropriate type. For example, types of liquid may include ink, paint, liquid containing conductive particles, chemicals, and disinfectants. Ink and paint may be distinguished based on whether or not they contain organic solvents and / or whether or not they have a function of protecting the surface of the object 101. However, such a distinction need not be made. In the following description, paint may be appropriately read as ink, and vice versa. Paint may contain pigments for the purpose of coloring, or may not contain pigments (colorless) without the purpose of coloring (for example, only for the purpose of imparting gloss and / or protecting the object 101).

[0015] The ejection device 1 has, for example, a head 3 that ejects droplets, and a moving unit 5 that moves the head 3 and the target object 101 relative to each other. The head 3 has an ejection surface 3a on which a plurality of nozzles (described later) that eject droplets are opened. The moving unit 5, for example, moves the ejection surface 3a and the surface of the target object 101 relatively along the ejection surface 3a and the surface of the target object 101 while maintaining the ejection surface 3a and the surface of the target object 101 facing each other. The direction of the relative movement is, for example, the D3 direction or the D6 direction. As can be understood from an inkjet printer, which is a specific example of the ejection device 1, droplets are ejected from the ejection surface 3a in synchronization with the above-mentioned relative movement, so that the droplets are deposited on an area larger than the area of ​​the arrangement region of the plurality of nozzles.

[0016] The ejection device 1 also has, for example, a tank 7 that stores liquid. The head 3 has a supply port 3b for supplying liquid from the tank 7 to the head 3 and a recovery port 3c for recovering liquid from the head 3 to the tank 7. That is, the liquid circulates through the head 3 and the tank 7. By circulating the liquid in this manner, for example, the likelihood of the liquid stagnation in the head 3 is reduced. Consequently, the likelihood of the stagnant liquid solidifying or of components in the stagnant liquid precipitating is reduced. Furthermore, in this embodiment, by circulating the liquid, the shear rate of the liquid can be adjusted, and therefore the viscosity of the liquid can be adjusted, as will be described later.

[0017] The discharge device 1 has a circulation actuator 9 that applies pressure to the liquid so that the liquid circulates, and a control unit 11 that controls each unit (e.g., the head 3, the moving unit 5, and the circulation actuator 9). The combination of the circulation actuator 9 and the control unit 11 may be considered as a flow rate setting unit 13 that sets the flow rate of the liquid circulating through the head 3 (hereinafter referred to as the circulation flow rate). The circulation flow rate may be considered to be the same as the flow rate of the liquid flowing out of the head 3 from the recovery port 3c, for example.

[0018] The ejection device 1 may have only one head 3 (and tank 7) as in a monochrome printer, or may have multiple heads 3 (and multiple tanks 7) that eject different types of liquid as in a color printer. The ejection device 1 may also have multiple heads 3 that eject the same type of liquid. Multiple heads 3 that eject the same type of liquid are advantageous, for example, in shortening the time it takes to deposit liquid on a certain area and improving dot density. For convenience, the following description will refer to only one head 3.

[0019] (moving part) The moving unit 5 can, for example, move the target object 101 relative to the head 3 in at least one of the directions D3 and D6. As described above, this direction is the movement direction when ejecting droplets, which is the so-called sub-scanning direction. The moving unit 5 may also be capable of realizing relative movement between the head 3 and the target object 101 in directions other than the directions D3 and D6. Other directions in which relative movement may be realized include, for example, the directions D2 and D5 orthogonal to the directions D3 and D6, and directions orthogonal to the ejection surface 3a (directions that move the head 3 and the target object 101 closer to each other, and directions that move them away from each other). The moving unit 5 may also be capable of realizing relative rotation between the head 3 and the target object 101.

[0020] The moving unit 5 may move only the target object 101, only the head 3, or both in the absolute coordinate system. The specific configuration of the moving unit 5 may be set appropriately depending on the specific type of the discharge device 1.

[0021] For example, if the discharge device 1 is a so-called line printer, the moving unit 5 may be configured as a device that transports a recording medium (e.g., paper) as the target object 101. This device includes, for example, a plurality of rollers that come into contact with the recording medium to generate frictional force, and an electric motor that rotates the plurality of rollers. Also, for example, if the discharge device 1 is a so-called serial printer, the moving unit 5 may include a device that transports the recording medium as the target object 101 in a predetermined transport direction, and a device that moves the head 3 in a direction perpendicular to the transport direction and along the recording medium.

[0022] Furthermore, for example, the discharge device 1 may include a belt conveyor that transports any type of object 101. Furthermore, for example, the discharge device 1 may include a movable table on which any type of object 101 is placed. Furthermore, for example, the discharge device 1 may include an industrial robot that moves any type of object 101 and / or an industrial robot that moves the head 3. Examples of industrial robots include vertical articulated robots (articulated robots in the narrow sense), SCARA robots, Cartesian robots, and parallel link robots.

[0023] (Tank and circulation unit) The tank 7 and the circulation unit 9 may be, for example, similar to a tank and a circulation unit in a known inkjet printer that circulates liquid, or may be an application of such a known tank and a circulation unit.

[0024] For example, the tank 7 may be configured to accommodate the liquid supplied to the head 3 and the liquid recovered from the head 3 in the same space. Alternatively, the tank 7 may be configured to accommodate the liquid supplied to the head 3 and the liquid recovered from the head 3 in separate spaces, with the liquid flowing from the latter space to the former space. In this case, the tank 7 may have two spaces separated by a partition wall, or may have two spaces by having two tanks connected to each other by a flow path. The inside of the tank 7 (the above-mentioned space) may be open to the atmosphere or may be sealed. In the latter case, the pressure inside the tank 7 may be adjusted to an appropriate pressure using a valve, a vacuum pump, or the like. The tank 7 may have a main tank and a sub-tank with a smaller capacity than the main tank. The sub-tank acts as an intermediate between the main tank and the head 3.

[0025] In the illustrated example, the circulation actuator 9 includes a pump 15 that delivers the liquid from the tank 7 to the head 3, a pressure sensor 17A that detects the pressure of the liquid on the supply port 3b side, and a pressure sensor 17B that detects the pressure of the liquid on the recovery port 3c side. The controller 11 feedback-controls the pump 15 based on the detected values ​​of the pressure sensors 17A and 17B, for example, so that the pressure difference between the supply port 3b and the recovery port 3c converges to a predetermined target value. This feedback-controls the circulation flow rate to the target flow rate.

[0026] Unlike the illustrated example, instead of or in addition to the pump 15 on the supply port 3b side, a pump 15 may be provided that delivers the liquid from the recovery port 3c to the tank 7. Also, instead of or in addition to the pump 15 that delivers the liquid, a liquid flow may be generated by controlling the pressure inside the tank 7 with a vacuum pump or the like. A liquid flow may also be generated by raising the liquid level in the tank that contains the supply liquid higher than the liquid level in the tank that contains the recovered liquid.

[0027] Instead of or in addition to pressure sensors 17A and 17B, a flow rate sensor that detects the flow rate of liquid supplied to head 3 and / or a sensor that detects the flow rate of liquid recovered from head 3 may be provided and used to control the circulation flow rate. Also, as will be understood from the various aspects of generating the liquid flow described above, instead of or in addition to these sensors, a sensor that detects the air pressure inside tank 7 may be provided and used to control the circulation flow rate. Open-loop control may be performed without sensor-based feedback control. In other words, sensors may not be provided.

[0028] The tank 7 and the circulation actuator 9 are not moved in the absolute coordinate system by the moving unit 5, for example. Therefore, for example, in an embodiment in which the moving unit 5 moves the head 3 in the absolute coordinate system, the head 3 moves relative to the tank 7 and the circulation actuator 9. In this case, the head 3, the tank 7, and the circulation actuator 9 may be connected by a flow path formed of, for example, a flexible tube. Also, in an embodiment in which the moving unit 5 does not move the head 3 in the absolute coordinate system, the head 3 is fixed relative to the tank 7 and the circulation actuator 9. In this case, the flow path connecting the head 3, the tank 7, and the circulation actuator 9 may have any configuration. Unlike the above description, all or part of the tank 7 and the circulation actuator 9 may move together with the head 3.

[0029] (Control unit) The control unit 11 is configured by, for example, a computer. The computer has a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and an external storage device, all of which are not shown. The head 3, the moving unit 5, and the circulation operating unit 9 are controlled by the CPU executing a program stored in the ROM and / or the external storage device.

[0030] (head) FIG. 2( a ) is an exploded perspective view of the head 3 .

[0031] The head 3 has a flow path member 19 (reference numeral shown in FIG. 1) having a flow path through which the liquid flows, an actuator 21 that applies pressure to the liquid in the flow path member 19, and a signal transmission member 23 (not shown in FIG. 1) for inputting a drive signal to the actuator 21. The flow path member 19 has a first flow path member 25 having a discharge surface 3a, and a second flow path member 27 having a supply port 3b and a recovery port 3c. The surface of the first flow path member 25 opposite to the discharge surface 3a is sometimes referred to as a pressure surface 25a.

[0032] The first flow path member 25 and the second flow path member 27 are each configured in a generally flat plate shape, and are stacked on top of each other to form the generally flat flow path member 19. The liquid supplied to the supply port 3b is supplied from the second flow path member 27 to the first flow path member 25, and is then ejected from the ejection surface 3a. The liquid that remains without being ejected flows from the first flow path member 25 to the second flow path member 27 and is recovered from the recovery port 3c.

[0033] The control unit 11 outputs a control signal based on predetermined data such as image data. The control signal is input, for example, via a signal transmission member 23 to a driver (not shown) mounted on the signal transmission member 23. The driver generates a drive signal having a predetermined waveform based on the input control signal. The drive signal is input to the actuator 21 via the signal transmission member 23. The actuator 21 applies pressure to the liquid in the flow path member 19 with a pressure waveform corresponding to the waveform of the drive signal. This causes the liquid in the flow path member 19 to be ejected from the ejection surface 3a. The roles of the control unit 11 and the driver may be appropriately determined, and the driver may be considered to be part of the control unit 11.

[0034] (Second flow path member, supply reservoir and recovery reservoir) Fig. 2(b) is a perspective view of the second flow path member 27. More specifically, this figure shows the second flow path member 27 as seen from the first flow path member 25 side, and the upper side of Fig. 2(b) corresponds to the lower side of Fig. 1 and Fig. 2(a). Fig. 3(a) is a planar perspective view of the head 3 as seen from the side opposite to the ejection surface 3a. In this figure, the shape of the second flow path member 27 and the actuator 21 are shown.

[0035] As shown in FIG. 2(b), the second flow path member 27 has two grooves (see reference numerals 29 and 31) formed on the surface facing the first flow path member 25. These two grooves are closed by the first flow path member 25 and constitute a supply reservoir 29 and a recovery reservoir 31 shown in FIGS. 2(b) and 3(a). The supply reservoir 29 is in communication with the supply port 3b, and is a flow path that supplies the liquid supplied to the supply port 3b to the flow path of the first flow path member 25. The recovery reservoir 31 is in communication with the recovery port 3c, and is a flow path that recovers the liquid from the flow path of the first flow path member 25 and leads the recovered liquid to the recovery port 3c.

[0036] The supply reservoir 29 and the recovery reservoir 31 have, for example, portions (main portions 29a and 31a) that extend linearly along the longitudinal direction (D2 direction and D5 direction) of the head 3. The main portions 29a and 31a have, for example, a length that spans the length of the longitudinal direction (D2 direction and D5 direction) of the arrangement area (see the arrangement area of ​​the actuator 21 in FIG. 3(a)) of a plurality of nozzles (described later). Furthermore, the main portions 29a and 31a are located on opposite sides (D3 direction and D6 direction) of the arrangement area of ​​the plurality of nozzles in the lateral direction of the head 3. In explaining the embodiments, for convenience, the shapes and dimensions of the supply reservoir 29 and the recovery reservoir 31 may be explained by focusing only on the main portions 29a and 31a.

[0037] The supply port 3b, for example, communicates with one end (the end in the D2 direction) of the supply reservoir 29. The other end (the end in the D5 direction) of the supply reservoir 29 is a dead end (in other words, a dead end). The liquid in the supply reservoir 29 flows in the direction from the one end to the other end (in the D5 direction). The recovery port 3c, for example, communicates with one end (the end in the D5 direction) of the recovery reservoir 31. The other end (the end in the D2 direction) of the recovery reservoir 31 is a dead end (in other words, a dead end). The liquid in the recovery reservoir 31 flows in the direction from the other end to the one end (in the D5 direction). In the illustrated example, the direction in which the liquid in the supply reservoir 29 flows and the direction in which the liquid in the recovery reservoir 31 flows are the same. However, the two directions may be reversed.

[0038] The supply reservoir 29 may have only the main portion 29a, or may have other portions. In the illustrated example, the supply reservoir 29 has a portion (reference numeral omitted) that extends obliquely from the main portion 29a in the longitudinal direction of the head 3 to the supply port 3b. Similarly, the recovery reservoir 31 may have only the main portion 31a, or may have other portions. In the illustrated example, the recovery reservoir 31 has a portion (reference numeral omitted) that extends obliquely from the main portion 31a in the longitudinal direction of the head 3 to the recovery port 3c.

[0039] The cross-sectional shapes and dimensions of the supply reservoir 29 and the recovery reservoir 31 (for example, the main portions 29a and 31a thereof) may be constant regardless of the position in the longitudinal direction of these flow paths, or may vary depending on the position. In the description of the embodiments, the former may be taken as an example. The cross-sectional shape may also be an appropriate shape such as a rectangle. The various dimensions of the supply reservoir 29 and the recovery reservoir 31 may be set appropriately depending on the specific technical field to which the discharge device 1 is applied.

[0040] In the illustrated example, the second flow path member 27 has two grooves that serve as the supply reservoir 29 and the recovery reservoir 31, as well as a slit 27a (FIGS. 2(a) and 2(b)) through which the signal transmission member 23 is inserted, and a recess 27b (FIGS. 2(b) and 3(a)) that houses the actuator 21. The slit 27a, for example, penetrates the second flow path member 27 from the first flow path member 25 side to the opposite side, and extends along the longitudinal direction of the head 3. The recess 27b has, for example, a planar shape that is slightly larger than the actuator 21, and in the illustrated example, is a rectangle whose longitudinal direction is the longitudinal direction of the head 3.

[0041] Any material may be used for the second flow path member 27. For example, the second flow path member 27 may be made of metal, resin, ceramic, or a combination of these.

[0042] (First flow path member) Fig. 3(b) is a planar perspective view of the head 3. This view shows the shape of the first flow path member 25 and the actuator 21. Also, Fig. 4 is an enlarged view of region IV in Fig. 3(b).

[0043] The flow paths of the first flow path member 25 have a plurality of supply manifolds 33 to which liquid is supplied from a supply reservoir 29, and a plurality of individual flow paths 35 to which liquid is supplied from the supply manifold 33. The individual flow paths 35 include nozzles (described below) that eject droplets from the ejection surface 3a. The flow paths of the first flow path member 25 also have a plurality of recovery manifolds 37 that recover liquid from the plurality of individual flow paths 35 and guide the recovered liquid to a recovery reservoir 31.

[0044] Although not specifically shown, the first flow path member 25 may also have flow paths located in the D2 and D5 directions relative to the plurality of supply manifolds 33, the plurality of individual flow paths 35, and the plurality of recovery manifolds 37, and connecting the supply reservoir 29 and the recovery reservoir 31. Such flow paths contribute to, for example, uniforming the temperature of the first flow path member 25.

[0045] (manifold) The supply manifold 33 has, for example, a main portion 33a (corresponding to substantially the entire supply manifold 33 in the illustrated example) that extends linearly along the D4 direction from the supply reservoir 29 side to the collection reservoir 31 side. The D4 direction is inclined with respect to the short-side direction (D6 direction) of the head 3. Similarly, the collection manifold 37 has, for example, a main portion 37a (corresponding to substantially the entire collection manifold 37 in the illustrated example) that extends linearly along the D1 direction from the collection reservoir 31 side to the supply reservoir 29 side. The D1 direction is inclined with respect to the short-side direction (D3 direction) of the head 3. In explaining the embodiments, for convenience, the shapes and dimensions of the supply manifold 33 and the collection manifold 37 may be explained by focusing only on the main portions 33a and 37a.

[0046] One end (end in the D1 direction) of the supply manifold 33 overlaps with the supply reservoir 29 in a plan view. This end communicates with the supply reservoir 29 via an opening 33b that opens into the surface of the first flow path member 25 on the side of the second flow path member 27. The other end (end in the D4 direction) of the supply manifold 33 is a dead end. Therefore, the liquid in the supply reservoir 29 is supplied to the one end of the supply manifold 33 via opening 33b and flows through the supply manifold 33 in the direction from the one end to the other end (direction D4).

[0047] One end (the end in the D4 direction) of the collection manifold 37 overlaps with the collection reservoir 31 in a plan view. This end communicates with the collection reservoir 31 via an opening 37b that opens into the surface of the first flow path member 25 on the side of the second flow path member 27. The other end (the end in the D1 direction) of the collection manifold 37 is a dead end. Therefore, the liquid in the collection manifold 37 flows from the other end to the one end (in the D4 direction) and is collected into the collection reservoir 31 via opening 37b.

[0048] The supply manifold 33 and the recovery manifold 37 have lengths spanning the length in the short direction (directions D3 and D6) of the arrangement area (here, see the arrangement area of ​​the actuators 21) of the multiple nozzles (described below). Note that the end of the supply manifold 33 on the recovery reservoir 31 side (end in the direction D4) is located, for example, closer to the supply reservoir 29 than the recovery reservoir 31. Similarly, the end of the recovery manifold 37 on the supply reservoir 29 side (end in the direction D1) is located, for example, closer to the recovery reservoir 31 than the supply reservoir 29.

[0049] The multiple supply manifolds 33 have, for example, the same configuration as one another and are arranged at a constant pitch along the D2 direction. In other words, the multiple supply manifolds 33 extend parallel to one another and have the same length. The connection positions (openings 33b) of the multiple supply manifolds 33 to the supply reservoir 29 are arranged at a constant pitch along the supply reservoir 29.

[0050] Similarly, the multiple collection manifolds 37 have, for example, the same configuration and are arranged at a constant pitch along direction D2. In other words, the multiple collection manifolds 37 extend parallel to one another and have the same length. The connection positions (openings 37b) of the multiple collection manifolds 37 to the collection reservoir 31 are arranged at a constant pitch along the collection reservoir 31.

[0051] The supply manifolds 33 and the collection manifolds 37 are alternately arranged at a fixed pitch, for example. The supply manifolds 33 and the collection manifolds 37 are adjacent to each other and extend parallel to each other. More specifically, most of the supply manifolds 33, excluding the upstream side, and most of the collection manifolds 37, excluding the downstream side, are adjacent to each other in the arrangement region of the nozzles.

[0052] The cross-sectional shapes and dimensions of the supply manifold 33 and the collection manifold 37 (for example, the main portions 33a and 37a thereof) may be constant regardless of the position in the longitudinal direction of these flow paths, or may vary depending on the position. In the description of the embodiments, the former may be taken as an example. The cross-sectional shape may be an appropriate shape such as a rectangle. The various dimensions of the supply manifold 33 and the collection manifold 37 may be set appropriately depending on the specific technical field to which the discharge device 1 is applied.

[0053] (Individual flow path) The individual flow paths 35 are, for example, located roughly between the supply manifold 33 and the collection manifold 37 adjacent to each other and connected to both. A plurality of individual flow paths 35 are provided for each set of manifolds (33 and 37). The plurality of individual flow paths 35 connected to the same manifold (33 and 37) are, for example, arranged at a constant pitch along the manifold (along the D1 direction) to form a single flow path row. The plurality of flow path rows are then arranged in the D2 direction, thereby arranging the plurality of individual flow paths 35 in a matrix. Unlike the example shown in the figure, two or more rows of individual flow paths 35 may be provided between the supply manifold 33 and the collection manifold 37 adjacent to each other.

[0054] Within one flow path array, the configuration of the multiple individual flow paths 35 is basically the same. Furthermore, the configurations of the multiple flow path arrays are also basically the same. However, for example, the orientation of the individual flow paths 35 may be different between adjacent flow path arrays (as shown in the example). Furthermore, for example, within one flow path array, the shapes and / or dimensions of the multiple individual flow paths 35 may be slightly different. Of the multiple flow path arrays, the flow path array located at the end in the D2 direction and the flow path array located at the end in the D5 direction may have so-called dummy individual flow paths that do not eject droplets.

[0055] Each individual flow path 35 has nozzles 43 that open to the ejection surface 3a and eject droplets. A row in which multiple nozzles 43 are arranged in the D1 direction is referred to as a nozzle row. The arrangement direction (D1 direction) of the nozzles 43 in the nozzle row is inclined with respect to the direction of relative movement of the head 3 with respect to the target object 101 (D3 direction). Due to the inclination, the nozzles 43 belonging to the same nozzle row are positioned differently in the D2 direction. Furthermore, the multiple nozzle rows partially overlap each other when viewed in the D3 direction. In this overlapping portion, the nozzles 43 in one nozzle row and the nozzles 43 in another nozzle row are positioned differently in the D2 direction. Furthermore, when the multiple nozzles 43 are projected in the D3 direction, the multiple nozzles 43 are aligned at essentially regular intervals in the D2 direction.

[0056] This makes it possible to form a plurality of dots arranged in the direction D2 at a pitch shorter than the distance between adjacent nozzles 43 in the head 3 on the surface of the object 101. For example, 32 nozzles 43 are projected within the range of the imaginary line R, and the nozzles 43 are arranged at intervals of 360 dpi within the imaginary line R. This makes it possible to print at a resolution of 360 dpi by ejecting droplets by moving the object 101 and the head 3 relative to each other in a direction perpendicular to the imaginary line R.

[0057] Fig. 5 is a perspective view of the individual flow path 35. Figs. 6(a) and 6(b) are cross-sectional views of the first flow path member 25 and the actuator 21. Fig. 6(a) corresponds to line VIa-VIa in Fig. 5. Fig. 6(b) corresponds to line VIb-VIb in Fig. 5.

[0058] The individual flow paths 35 have, for example, supply flow paths 39 (first supply flow paths 39A and second supply flow paths 39B) connected to the supply manifold 33, pressure chambers 41 connected to the supply flow paths 39, and nozzles 43 connected to the pressure chambers 41. As described above, the nozzles 43 open to the ejection surface 3a and communicate with the outside of the first flow path member 25. The liquid in the supply manifold 33 is supplied to the nozzles 43 via the supply flow paths 39 and the pressure chambers 41. Then, when pressure is applied to the pressure chambers 41 by the actuator 21, droplets are ejected from the nozzles 43. The individual flow paths 35 also have recovery flow paths 45 connecting the pressure chambers 41 and the recovery manifold 37. Liquid that is not ejected and remains in the pressure chambers 41 is recovered from the recovery flow path 45 to the recovery manifold 37.

[0059] The pressure chamber 41 has, for example, a pressure chamber main body 41 a to which pressure is applied by the actuator 21 , and a descender 41 b that connects the pressure chamber main body 41 a and the nozzle 43 .

[0060] The pressure chamber main body 41a opens, for example, to the pressure applying surface 25a of the first flow path member 25 and is closed by the actuator 21. Pressure is applied to the liquid in the pressure chamber main body 41a as the actuator 21 flexes and deforms upward and / or downward. The descender 41b extends from the lower surface of the pressure chamber main body 41a toward the ejection surface 3a. The area of ​​the cross section of the descender 41b is smaller than the area of ​​the cross section of the pressure chamber main body 41a parallel to the pressure applying surface 25a.

[0061] The shape and dimensions of the pressure chamber body 41a may be set as appropriate. In the illustrated example, the planar shape of the pressure chamber body 41a is circular. Unlike the illustrated example, the planar shape of the pressure chamber body 41a may be a shape other than circular, such as an ellipse or a diamond. Furthermore, the pressure chamber body 41a has a thin shape in which the thickness is smaller than the diameter in a planar view. In the illustrated example, the shape and dimensions of a cross section of the pressure chamber body 41a parallel to the pressure application surface 25a are constant in the vertical direction. However, the shape and / or dimensions of the cross section of the pressure chamber body 41a may vary depending on the position in the vertical direction.

[0062] The shape and dimensions of the descender 41b may also be set appropriately. In the illustrated example, the shape of the descender 41b is a straight column. Also, in the illustrated example, the cross-sectional shape is circular. Unlike the illustrated example, the descender 41b may be inclined in the vertical direction, or the diameter may vary depending on the vertical position. Also, the cross-sectional shape may be a shape other than a circle, such as an ellipse.

[0063] The connection position of the descender 41b to the pressure chamber main body 41a in a plan view may also be set appropriately. In the illustrated example, the descender 41b is connected adjacent to the outer edge of the circular pressure chamber main body 41a. Unlike the illustrated example, if the pressure chamber main body 41a has an elliptical or diamond shape, for example, the descender 41b may be connected to an end of the pressure chamber main body 41a in the longitudinal direction.

[0064] The nozzle 43 opens to a portion of the bottom surface of the descender 41b. For example, the nozzle 43 may open to the center of the bottom surface of the descender 41b, or may open to a position away from the center (as shown in the example). The vertical cross section of the nozzle 43 is tapered so that the diameter decreases toward the ejection surface 3a. However, the nozzle 43 may be partially or entirely reverse tapered. The cross section of the nozzle 43 is, for example, circular.

[0065] The supply flow path 39 has, for example, a first supply flow path 39A and a second supply flow path 39B. Unlike the example shown in the figure, the supply flow path 39 may have only one of the first supply flow path 39A and the second supply flow path 39B. In the supply flow path 39, the connection position with respect to the supply manifold 33, the connection position with respect to the pressure chamber 41, the flow path shape and dimensions may be set appropriately. In the example shown in the figure, they are as follows.

[0066] The first supply flow path 39A connects the supply manifold 33 and the pressure chamber main body 41a. The first supply flow path 39A extends upward from the upper surface of the supply manifold 33, then extends in the D5 direction, extends in the D4 direction, and then extends upward again to connect to the lower surface of the pressure chamber main body 41a. The shape and dimensions of the cross section of the first supply flow path 39A are generally constant over most of the length of the first supply flow path 39A (for example, more than 60%). The shape of the cross section over this most part is rectangular.

[0067] The second supply flow path 39B connects the supply manifold 33 and the descender 41b. The second supply flow path 39B extends from the lower surface of the supply manifold 33 in the direction D5, then extends in the direction D1, and then connects to the side surface of the descender 41b. The shape and dimensions of the cross section of the second supply flow path 39B are generally constant over most of the length of the second supply flow path 39B (e.g., 60% or more). The cross section over most of this length is rectangular.

[0068] For example, only one recovery flow path 45 is provided for each individual flow path 35. Unlike the illustrated example, two or more recovery flow paths 45 may be provided. In the recovery flow path 45, the connection position to the recovery manifold 37, the connection position to the pressure chamber 41, the flow path shape and dimensions may be set appropriately. In the illustrated example, they are as follows.

[0069] The recovery channel 45 connects the recovery manifold 37 and the descender 41b. The recovery channel 45 extends from the side of the recovery manifold 37 in the direction D2, then extends in the direction D4, and then connects to the side of the descender 41b. The shape and dimensions of the cross section of the recovery channel 45 are generally constant over most of the length of the recovery channel 45 (for example, more than 60%). The shape of the cross section over this most part is rectangular.

[0070] As described above, the individual flow paths 35 connected to the same supply manifold 33 and the same recovery manifold 37 are arranged at a constant pitch along the manifolds. Therefore, the connection positions between the first supply flow paths 39A and the supply manifold 33 are aligned at a constant pitch along the supply manifold 33. The same is true for the connection positions between the second supply flow paths 39B and the supply manifold 33, and the connection positions between the recovery flow paths 45 and the recovery manifold 37.

[0071] As shown in Figures 6(a) and 6(b), first flow path member 25 is formed by stacking multiple plates 47A to 47M. The various flow paths of first flow path member 25 are formed by holes or recesses formed in plates 47A to 47M. The multiple plates 47A to 47M may be made of, for example, metal or resin. In the example shown in Figure 6(b), dampers (reference numerals omitted) are provided above and below collection manifold 37.

[0072] As described above, the pressure chamber 41 opens to the pressure surface 25a. Unlike the illustrated example, a plate may be provided to close the pressure chamber 41. In this case, however, it can also be considered as a question of whether the plate closing the pressure chamber 41 is considered to be part of the first flow path member 25 or part of the actuator 21. In the description of the present disclosure, such a plate is considered to be part of the actuator 21.

[0073] (actuator) As shown in FIG. 2(a), the actuator 21 is, for example, a substantially flat plate-shaped member, and is joined to the pressure surface 25a of the first flow path member 25 (more specifically, the area indicated by the dotted line in FIG. 2(a)). As shown in FIGS. 6(a) and 6(b), the actuator 21 closes the upper opening of the pressure chamber 41. The actuator 21 basically extends over the arrangement area of ​​all the pressure chambers 41. The actuator 21 has a displacement element 49 for each pressure chamber 41.

[0074] The configuration of the actuator 21 may be any of various known configurations or applications of known configurations. In the illustrated example, the actuator 21 is a so-called unimorph type piezoelectric actuator. Specifically, it is as follows.

[0075] The actuator 21 has a vibration plate 51, a common electrode 53, a piezoelectric layer 55, and an individual electrode 57, which are layered in this order from the pressure chamber 41 side. The vibration plate 51, the common electrode 53, and the piezoelectric layer 55 basically extend over the area where all of the pressure chambers 41 are arranged. An individual electrode 57 is provided for each pressure chamber 41. For example, in a planar perspective view, the individual electrode 57 has a shape similar to the planar shape of the pressure chamber 41, and overlaps the center of the pressure chamber 41.

[0076] The portion of the piezoelectric layer 55 sandwiched between the individual electrode 57 and the common electrode 53 is polarized in the thickness direction. Therefore, when a voltage is applied to the individual electrode 57 and the common electrode 53, the piezoelectric layer 55 contracts or expands in a direction along the surface. This contraction or expansion is regulated by the vibration plate 51, and the displacement element 49 bends toward or away from the pressure chamber 41 like a bimetal. This applies pressure to the liquid in the pressure chamber 41.

[0077] The material and thickness of each layer of the actuator 21 may be set as appropriate. For example, the diaphragm 51 and the piezoelectric layer 55 may be made of lead zirconate titanate (PZT), NaNbO, BaTiO, (BiNa)NbO, BiNaNbO, 15 The common electrode 53 and the individual electrodes 57 may be made of a metal material such as an Ag—Pd or Au material.

[0078] For example, a constant potential (reference potential) is applied to the common electrode 53. For example, the above-mentioned drive signal is input to the individual electrodes 57. The drive method of the displacement elements 49 (or, from another perspective, the waveform of the drive signal) may be any appropriate method. For example, the drive method may be a so-called push-pull type.

[0079] (liquid) 7 is a diagram showing the characteristics of the liquid used in the discharge device 1. In this diagram, the horizontal axis represents shear rate D (1 / s), and the vertical axis represents viscosity η (Pa s). EX1 and EX2 represent the characteristics of a first example and a second example of the liquid used in the discharge device 1.

[0080] As shown in this diagram, the liquid used in the discharge device 1 is a pseudoplastic fluid. Specifically, pseudoplastic fluids are non-Newtonian fluids whose viscosity decreases as the shear rate increases. Shear rate is also referred to as shear rate, velocity gradient, or strain rate. For example, shear rate can be calculated simply as the difference in velocity between two positions spaced apart in a direction perpendicular to the flow direction, divided by the distance between the two positions. Viscosity can be calculated simply as the shear stress divided by the shear rate. Shear stress is also referred to as shear stress. For example, shear stress can be calculated simply as the force acting to displace two parallel surfaces (with the same area) spaced apart in a direction perpendicular to the flow direction, in the flow direction, divided by the area of ​​one of the surfaces.

[0081] In addition, the viscosity of pseudoplastic fluid is expressed as η = k × D p-1 When approximated by a power law, the exponent p is less than 1, so it can be said to be a power law fluid. Here, k is the viscosity coefficient and D is the shear rate. Note that viscosity η is also called apparent viscosity because it is a function of D.

[0082] The liquid used in the discharge device 1 may or may not have thixotropy, which means that the viscosity decreases as the time during which it is subjected to shear stress increases.

[0083] The specific components and / or composition of the pseudoplastic fluid may be various known ones or may be an application of known ones. For example, ink and paint are generally pseudoplastic fluids. The liquids according to the first and second examples whose properties are shown in FIG. 7 are common paints (in other words, paints available on the market). The specific properties of the pseudoplastic fluid may also be appropriately determined. An example is given below.

[0084] For example, a liquid can move at a shear rate of 1000 s -1 The viscosity at the shear rate of 1000 s may be 0.02 Pa·s or more and 0.4 Pa·s or less. In the paint according to the first example whose characteristics are shown in FIG. 7, -1 The viscosity is 0.3 Pa·s when the shear rate is 1000 s -1 The viscosity of the liquid is 0.1 Pa·s when the shear rate is 1000 s -1 The viscosity at this time may be 0.1 Pa·s or more and 0.3 Pa·s or less.

[0085] For example, the shear rate of a liquid is 0.01 s -1 The viscosity at shear rate of 0.01 s to 50 Pa s may be set to 0.5 Pa s or more and 50 Pa s or less. In the paint according to the first example whose characteristics are shown in FIG. 7, -1 The viscosity is 5 Pa·s when the shear rate is 0.01 s -1 The viscosity of the liquid is 30 Pa·s when the shear rate is 0.01 s -1 The viscosity at this time may be 5 Pa·s or more and 30 Pa·s or less.

[0086] Furthermore, for example, when the viscosity of a liquid is approximated by a power law, the viscosity coefficient k may be 1.0 or more and 1.5 or less, and the power exponent p may be 0.35 or more and 0.65 or less. In the paint according to the first example, the viscosity coefficient k is 1.0 and the power exponent p is 0.65. In the paint according to the second example, the viscosity coefficient k is 1.5 and the power exponent p is 0.35. The approximation formula may be determined, for example, by the least squares method.

[0087] (average viscosity) Below, the concept of average viscosity is introduced. Viscosity essentially exhibits different values ​​for each minute region in the flow path. However, the viscosity for each minute region is not necessarily suitable for setting the viscosity of the liquid in the flow path member 19, and its calculation can also be difficult. Therefore, the viscosity averaged for each portion of the flow path of the flow path member 19 is referred to as the average viscosity. The average viscosity is one value for one portion in the flow path. For example, the average viscosity of one supply manifold 33 refers to the average viscosity for the entire supply manifold 33.

[0088] The average viscosity may be calculated, for example, as follows. First, the relationship between the shear rate D and the viscosity η of the liquid used in the discharge device 1 is identified. In this identification, various known methods may be employed, or known literature may be referenced. Next, an approximate equation is found that expresses the identified relationship between the shear rate D and the viscosity η. The approximate equation may be an appropriate one, such as a power law. The fitting method may also be a known one, such as the least squares method. Next, the circulation flow rate U (m 3 / s) as the boundary condition, a fluid simulation is performed for each part of the flow path using the above approximate formula to find the differential pressure ΔP (Pa) between the upstream and downstream ends of each part.Then, the circulation flow rate U, differential pressure ΔP, and the dimensions (m) of each part are substituted into the specified formula to calculate the average viscosity μ (Pa s).

[0089] An example of a formula for calculating the average viscosity μ is shown below:

[0090] The formula when the flow path shape is a cylinder with the flow direction as the axial direction is as follows: U=(πr 4 ΔP) / (8 μL) (1) where r is the radius of the cross section and L is the length of the flow path.

[0091] Furthermore, when the flow path is shaped like a prism (rectangular parallelepiped) with the flow direction as the axial direction, the formula is as follows: U=(w 3hΔP) / (4 μL) ×(16 / 3-1024 / π 5 ×w / h ×Σ(1 / q 5 ×tanh(qπh / 2w)) (2) Here, q = 1, 3, 5, 7, 9, and 11, and Σ is the six (1 / q 5 × tanh(qπh / 2w)). w is the width of the channel. h is the height of the channel. L is the length of the channel.

[0092] The flow rate U differs between the upstream and downstream sides of the reservoirs (29 and 31) and the manifolds (33 and 37). In this case, for example, the highest flow rate, the lowest flow rate, or the average flow rate may be used. The average viscosity in the following description may be considered to be calculated using any of the above flow rates. When comparing the average viscosity of the reservoirs (29 and 31) with the average viscosity of the manifolds (33 and 37), average viscosities calculated under the same conditions may be compared. For example, average viscosities calculated using the highest flow rates (lowest average viscosities) may be compared, average viscosities calculated using the lowest flow rates (highest average viscosities) may be compared, or average viscosities calculated using average flow rates (average average viscosities) may be compared. For example, the average viscosity in the following description may be considered to be the average viscosity calculated using the highest flow rate (lowest average viscosity). For example, the average viscosity of the supply reservoir 29 and the supply manifold 33 may be considered to be calculated using the most upstream flow rate. The average viscosity of the collection reservoir 31 and collection manifold 37 may be considered to be calculated using the most downstream flow rate.

[0093] The direction of the liquid flow is not necessarily constant in the pressure chamber 41, the pressure chamber main body 41a, or the descender 41b. In the following description, the average viscosity in these areas is calculated assuming that the flow direction is from top to bottom. For example, the average viscosity in the descender 41b is calculated assuming that the flow direction is from the pressure chamber main body 41a to the nozzle 43.

[0094] (Average viscosity in flow path material) 8 is a diagram showing an example of the relative relationship between the average viscosity μ of each portion of the flow path in the flow path member 19. In this diagram, the horizontal axis corresponds to the multiple portions of the flow path in the flow path member 19. The vertical axis indicates the average viscosity μ of each portion.

[0095] In the figure, the average viscosity μ2 indicates the average viscosity μ in one of the supply manifolds 33. Similarly, the average viscosity μ in one of the other flow paths is shown. The average viscosity μ3 of the supply flow path 39 may be regarded as the average viscosity of either the first supply flow path 39A or the second supply flow path 39B.

[0096] In the liquid ejection device 1, the target circulation flow rate controlled by the flow rate setting unit 13 and the shape and dimensions of the flow path of the flow path member 19 are set so that the relationship of average viscosity as shown in the figure is satisfied. In other words, the flow path of the flow path member 19 has a flow path shape that satisfies the relationship shown in Fig. 8 when the circulation flow rate is the target flow rate. In other words, in the shape and dimensions of the flow path of the flow path member 19, the circulation flow rate is set to a value that satisfies the relationship of average viscosity shown in Fig. 8. For example, in the shape and dimensions of the flow path of the flow path member 19, the circulation flow rate is set to a value that makes the average viscosity of the liquid in the supply flow path 39 less than half the average viscosity of the liquid in the supply manifold 33.

[0097] When the circulation flow rate is adjusted by open-loop control, the circulation flow rate fluctuates greatly due to the amount of droplets ejected from the multiple nozzles 43. In this case, the relationship shown in Fig. 8 may hold for the circulation flow rate when, for example, droplets are not being ejected from all nozzles 43. In other words, for a product being manufactured, the circulation flow rate when droplets are not being ejected from all nozzles 43 may be identified as the target flow rate for that product. This concept may also be applied to feedback control in which the circulation flow rate has low ability to track the target flow rate.

[0098] In FIG. 8, for example, the following relationship holds for the average viscosity:

[0099] The average viscosity μ3 of the liquid in the supply flow path 39 (39A or 39B) may be lower than the average viscosity μ2 of the liquid in the supply manifold 33. More specifically, for example, the average viscosity μ3 may be equal to or less than ½, ⅓, or ⅕ of the average viscosity μ2.

[0100] In this case, for example, because the average viscosity μ3 of the liquid in the supply flow path 39 is low, the liquid can be smoothly supplied from the supply flow path 39 to the pressure chamber 41. Furthermore, because the average viscosity μ2 is high inside the supply manifold 33, pressure waves are easily attenuated. As a result, the likelihood that a pressure wave leaking from a pressure chamber 41 to the supply manifold 33 via the supply flow path 39 will propagate to another pressure chamber 41 via another supply flow path 39 is reduced. In other words, so-called fluid crosstalk can be reduced.

[0101] A similar relationship to the above may also hold between recovery passageway 45 and recovery manifold 37. That is, the average viscosity μ5 of the liquid in recovery passageway 45 may be lower than the average viscosity μ6 of the liquid in recovery manifold 37. More specifically, the average viscosity μ5 may be set to be, for example, ½, ⅓, or ⅕ of the average viscosity μ6 or less. In this case, the same effect as above is achieved.

[0102] The average viscosity μ2 of the supply manifold 33 may be lower than the average viscosity μ1 of the supply reservoir 29. More specifically, for example, the average viscosity μ2 may be ½, ⅓, or ¼ of the average viscosity μ1.

[0103] In this case, for example, the low average viscosity μ2 of the liquid in the supply manifold 33 allows the liquid to be smoothly supplied from the supply manifold 33 to the supply flow path 39. Furthermore, since the viscosity is high in the supply reservoir 29 and pressure waves are easily attenuated, crosstalk due to the propagation of pressure waves through the supply reservoir 29 can be reduced.

[0104] A similar relationship to the above may also hold between collection manifold 37 and collection reservoir 31. That is, the average viscosity μ6 of the liquid in collection manifold 37 may be lower than the average viscosity μ7 of the liquid in collection reservoir 31. More specifically, the average viscosity μ6 may be set to be, for example, ½, ⅓, or ⅕ of the average viscosity μ7 or less. In this case, the same effect as above is achieved.

[0105] The average viscosity μ4 of the descender 41b may be set to be higher than the average viscosity μ5 of the recovery passageway 45. More specifically, for example, the average viscosity μ4 may be set to be 1.5 times or more the average viscosity μ5.

[0106] In this case, for example, if the viscosity is high, the resistance to the movement of the air bubbles increases, and therefore the probability that the air bubbles that have entered the descender 41b from the nozzle 43 can be recovered from the recovery channel 45 increases.

[0107] A similar relationship to the above may also be established between the descender 41b and the supply flow path 39. That is, the average viscosity μ4 of the descender 41b may be higher than the average viscosity μ3 of the supply flow path 39. More specifically, for example, the average viscosity μ4 may be 1.5 times or more or 2 times or more the average viscosity μ3.

[0108] In this case, for example, the liquid can be smoothly supplied to the descender 41b because the average viscosity μ3 of the supply flow path 39 is low. As a result, for example, the probability that the liquid supply to the descender 41b will not be able to keep up due to continuous ejection of the liquid is reduced.

[0109] The average viscosity μ2 of the supply manifold 33 may be set higher than the average viscosities (μ3, μ4, and μ5) of each flow path (excluding the pressure chamber main body 41a) of the individual flow paths 35. More specifically, for example, the average viscosity μ2 may be set to be 1.5 times or more higher than any of the average viscosities μ3, μ4, and μ5.

[0110] In this case, for example, the low average viscosity μ in the individual flow paths 35 allows the liquid to be smoothly supplied to the nozzles 43. Furthermore, the high average viscosity μ in the supply manifold 33 quickly attenuates the pressure leaking from the individual flow paths 35 to the supply manifold 33. Therefore, fluid crosstalk is less likely to occur.

[0111] A similar relationship to the above may also hold between collection manifold 37 and individual flow paths 35. That is, the average viscosity μ6 of the liquid in collection manifold 37 may be higher than the average viscosities (μ3, μ4, and μ5) of each of the flow paths of individual flow paths 35. More specifically, for example, the average viscosity μ6 may be 1.5 times or more the average viscosities μ3, μ4, and μ5. In this case as well, the same effect as above is achieved.

[0112] (Example of average viscosity value) There are countless combinations of liquid properties, circulation flow rate, flow path shape and dimensions, etc. that can realize the above-described relationship of average viscosity μ, and these may be set appropriately depending on the specific technical field to which the discharge device 1 is applied. Below, an example of values ​​when a general paint described with reference to Figure 7 is used is shown.

[0113] The circulation flow rate may be, for example, 50 ml / min to 300 ml / min. The pressure in the nozzle 43 when no liquid is being ejected may be ±2 kPa relative to atmospheric pressure (approximately 100 kPa). The pressure difference between the supply port 3b and the recovery port 3c may be 40 kPa to 160 kPa.

[0114] In each of the supply reservoir 29 and the recovery reservoir 31, the width w may be 4 mm or more and 20 mm or less, the height h may be 3 mm or more and 15 mm or less, and the length L may be 200 mm or more and 800 mm or less. In each of the supply manifold 33 and the recovery manifold 37, the width w may be 0.2 mm or more and 2 mm or less, the height h may be 0.5 mm or more and 6 mm or less, and the length L may be 5 mm or more and 20 mm or less. In the first supply flow path 39A, the width w and height h may be 50 μm or more and 200 μm or less. In the second supply flow path 39B, the width w may be 50 μm or more and 200 μm or less, and the height h may be 25 μm or more and 200 μm or less. In the recovery channel 45, the width w may be 70 μm or more and 200 μm or less, and the height h may be 80 μm or more and 200 μm or less. The length L of the supply channel 39 and the recovery channel 45 may be 300 μm or more and 1500 μm or less. In the descender 41b, the radius r may be 50 μm or more and 250 μm or less, and the length L may be 0.5 mm or more and 2 mm or less. In the nozzle 43, the radius r may be 5 μm or more and 50 μm or less.

[0115] An example of a calculation of the average viscosity μ under the above conditions is shown below. The average viscosity μ of the descender 41b was calculated using equation (1), and the average viscosity μ of the other flow paths was calculated using equation (2). The average viscosity μ of the supply reservoir 29 and the recovery reservoir 31 is 0.4 Pa·s or more and 2 Pa·s or less. The average viscosity μ of the supply manifold 33 and the recovery manifold 37 is 0.1 Pa·s or more and 0.4 Pa·s or less. The average viscosity μ of the supply flow path 39 and the recovery flow path 45 is 0.01 Pa·s or more and 0.1 Pa·s or less. The average viscosity μ of the descender 41b is 0.05 Pa·s or more and 0.2 Pa·s or less.

[0116] (fluid resistance) Fluid resistance in the flow path member 19 (N·s / m 5 ) may be set appropriately. For example, the fluid resistance may be set so that both the following conditions 1 and 2 are met.

[0117] Condition 1: (1 / 2) x R r ×U(1+1 / m) and (1 / 2) x R m The sum of ×(U / m)×(1+1 / n) is is smaller than 2σ / r. Condition 2: R r <1 / 10×R m ×(1 / m) where R r is the flow resistance of the liquid in the supply reservoir 29. R m is the fluid resistance of the liquid in the supply manifold 33. m is the number of supply manifolds 33 connected to the supply reservoir 29. n is the number of individual flow paths 35 (nozzles 43) for each supply manifold 33. U is the flow rate (m 3 / s), σ is the surface tension of the liquid (N / m), and r is the radius of the nozzle 43 (m).

[0118] Here, supply manifolds 33 connected only to dummy individual flow paths that are not capable of ejecting droplets are ignored. It is also assumed that the same number of nozzles 43 are connected to each supply manifold 33. It is also assumed that the pitch of the multiple supply manifolds 33, the distance from the upstream end of the supply reservoir 29 to the first supply manifold 33, and the distance from the last supply manifold 33 to the downstream end of the supply reservoir 29 are equal.

[0119] (1 / 2) × R in condition 1 r ×U(1+1 / m) corresponds to the pressure drop (the pressure difference between the upstream and downstream) in the supply reservoir 29. Specifically, the pressure drop from the upstream end of the supply reservoir 29 to the first supply manifold 33 is expressed as U×R r / m, the pressure drop from the first supply manifold 33 to the second supply manifold is (UU / m) × R r / m. The total pressure drop from the upstream end to the downstream end is calculated as U × R r / m+(UU / m)×R r / m+…+U / m× / R r / m, the above (1 / 2) × R r ×U(1+1 / m) is obtained.

[0120] (1 / 2) × R in condition 1 m ×(U / m)×(1+1 / n) corresponds to the pressure drop (the pressure difference between the upstream and downstream) in one supply manifold 33. This formula is obtained in the same way as the pressure drop in the supply reservoir 29 described above. That is, in the formula related to the supply reservoir 29, the fluid resistance R of the supply reservoir 29 is r is the fluid resistance R of the supply manifold 33 m , the flow rate U into supply reservoir 29 is replaced by the flow rate U / m of liquid entering supply manifold 33, and the number m of supply manifolds 33 is replaced by the number n of nozzles 43.

[0121] In condition 1, (1 / 2) × R r ×U(1+1 / m) and (1 / 2)×R m The sum of ×(U / m)×(1+1 / n) roughly corresponds to the pressure difference between the most upstream individual flow path 35 and the most downstream individual flow path 35. The most upstream individual flow path 35 is the individual flow path 35 connected most upstream of the supply manifold 33 connected most upstream of the supply reservoir 29. The most downstream individual flow path 35 is the individual flow path 35 connected most downstream of the supply manifold 33 connected most downstream of the supply reservoir 29. Since the pressure drops in the individual flow paths 35 are approximately equal among the multiple individual flow paths 35, the above sum corresponds to the pressure difference across all of the nozzles 43 (the pressure difference between the nozzle 43 with the highest pressure and the nozzle 43 with the lowest pressure).

[0122] When the above sum is smaller than 2σ / r, it is easy to maintain a meniscus under atmospheric pressure in all nozzles 43. As already mentioned, with regard to condition 1, the supply manifold 33 to which only dummy individual flow paths are connected and the dummy individual flow paths may be ignored. Also, the most upstream supply manifold 33 or the most downstream supply manifold 33 may have fewer individual flow paths 35 connected thereto than the other supply manifolds 33. In this case, for example, the most upstream supply manifold 33 or the most downstream supply manifold 33 may be ignored, or conversely, it may be assumed that the most upstream supply manifold 33 or the most downstream supply manifold 33 is connected to the same number of individual flow paths 35 as the other supply manifolds 33.

[0123] Condition 2 is the fluid resistance R of the supply reservoir 29. r and the fluid resistance R of the supply manifold 33 m The flow rate of the liquid flowing into the supply manifold 33 is 1 / m of the flow rate of the liquid flowing into the supply reservoir 29, so the fluid resistance R m Multiply by 1 / m to get the fluid resistance R r and fluid resistance R m The fact that condition 2 is met means that the fluid resistance R of the supply reservoir 29 is r is the fluid resistance R of the supply manifold 33 m This means that it is extremely small in comparison to

[0124] For example, in the prior art, R r is R m On the other hand, in this embodiment, R r is R m × (1 / m) or more and less than 1 / 10 of R r is R m It may be about 1 / 5 of ×(1 / m).

[0125] By satisfying condition 2, for example, liquid can easily flow from supply reservoir 29 to the positions of the plurality of supply manifolds 33, thereby reducing the difference in flow rate between the plurality of supply manifolds 33. Consequently, liquid can be stably supplied to all of the supply manifolds 33.

[0126] In addition to conditions 1 and 2, the fluid resistance may be set so that the following condition 3 is met. Condition 3: R m <1 / 10×R n ×(1 / n) where R n is the fluid resistance in the nozzle 43.

[0127] Condition 3 is the fluid resistance R of the supply manifold 33. m and the fluid resistance of the individual flow path 35. However, the fluid resistance R n is much larger than the fluid resistance of other parts of the individual flow path 35. Therefore, the fluid resistance of the individual flow path 35 is calculated by subtracting the fluid resistance R n In addition, since the flow rate of the liquid flowing into the individual flow paths 35 is 1 / n of the flow rate of the liquid flowing into the supply manifold 33, the fluid resistance R n Multiply by 1 / n to get the fluid resistance R m and fluid resistance R n It is compared with.

[0128] If condition 3 is satisfied, the fluid resistance R of the supply manifold 33 m is the fluid resistance R of the nozzle 43 n For example, in the prior art, R m is R n ×(1 / n) is approximately 1 / 6 of R m is R n × (1 / n) may be approximately 1 / 6. For example, R m is R n It can be between 1 / 10 and 1 / 4 of ×(1 / n).

[0129] By satisfying condition 3, for example, the liquid can easily flow from the supply manifold 33 to the positions of the plurality of individual flow paths 35, thereby reducing the difference in flow rate between the plurality of individual flow paths 35. Consequently, the liquid can be stably supplied to all of the individual flow paths 35.

[0130] The example of the dimensions of the flow path exemplified as an example of dimensions that realize the average viscosity shown in FIG. 8 may be referred to as an example of the dimensions of the flow path that satisfy conditions 1 to 3.

[0131] (Variation) FIG. 9 is a schematic cross-sectional view of an individual flow path 235 according to a modified example.

[0132] The pressure chamber 241 of the individual flow path 235 has a pressure chamber main body 241a and a descender 241b, similar to the pressure chamber 41 of the embodiment. However, the descender 241b has a first portion 241ba and a second portion 241bb that have different cross-sectional areas.

[0133] The first portion 241ba is connected to the nozzle 43. The second portion 241bb is connected to the pressure chamber main body 241a. In other words, the second portion 241bb is located closer to the pressure chamber main body 241a than the first portion 241ba. The cross-sectional area of ​​the second portion 241bb is larger than that of the first portion 241ba.

[0134] The first portion 241ba and the second portion 241bb have different average viscosities due to differences in cross-sectional area. For example, the average viscosity of the liquid in the second portion 241bb is higher than the average viscosity of the liquid in the first portion 241ba. In other words, the average viscosity in the descender 241b increases in stages as it approaches the pressure chamber main body 41a from the nozzle 43. The increase in average viscosity may be in two or more stages, not just one stage. In other words, the descender may have a third portion, etc., in addition to the first and second portions.

[0135] In the case where the average viscosity of the second portion 241bb, which is located closer to the pressure chamber main body 241a than the first portion 241ba, is higher than the average viscosity of the first portion 241ba as in this modified example, for example, it becomes difficult for air bubbles that have entered the descender 241b from the nozzle 43 to move toward the pressure chamber main body 241a, thereby reducing the likelihood that the air bubbles will remain in the pressure chamber main body 241a and cause a deterioration in the ejection characteristics.

[0136] Note that, if at least one of the two flow paths whose average viscosities are compared has a portion with a different shape, the average viscosities at the portion where the two flow paths contact may be compared. For example, in an individual flow path 235 according to a modified example, when comparing the average viscosity of the recovery flow path 45 with the average viscosity of the descender 241b, the average viscosity of the second portion 241bb directly connected to the recovery flow path 45 may be used for the comparison, rather than the average viscosity of the entire descender 241b. This is because it is the average viscosity of the second portion 241bb that has the greatest influence on the flow between the recovery flow path 45 and the descender 241b.

[0137] The technology according to the present disclosure is not limited to the above-described embodiment and modifications, and may be implemented in various modes.

[0138] For example, the liquid ejection device is not limited to a piezoelectric type that applies pressure to the liquid using a piezoelectric body, but may be a thermal type that uses heat to generate bubbles in the liquid and applies pressure to the liquid due to the generation of the bubbles to eject droplets.

[0139] The flow paths may have various configurations other than those shown in the drawings. For example, adjacent individual flow paths may share a portion. For example, a portion of the recovery flow path on the recovery manifold side may be shared by adjacent individual flow paths.

[0140] The average viscosity may also be set differently from that of the embodiment. For example, the average viscosity μ3 of the supply flow path 39 may be set greater than the average viscosity μ5 of the recovery flow path 45 or 1.5 times greater than that of the embodiment. In this case, the liquid in the descender 41b is less likely to flow backward (less likely to flow in the opposite direction to the circulation direction) when droplets are ejected. Furthermore, the liquid and / or air bubbles are more likely to flow in the recovery flow path. [Explanation of symbols]

[0141] 1...liquid ejection device, 3...head, 13...flow rate setting section, 19...flow path member, 21...actuator, 29...supply reservoir, 31...recovery reservoir, 33...supply manifold, 37...recovery manifold, 39...supply path, 41...pressure chamber, 43...nozzle, 45...recovery path.

Claims

1. The flow path includes a channel configured to carry a predetermined liquid having pseudoplastic properties, and the flow path is Supply reservoir, Multiple supply manifolds connected to the aforementioned supply reservoir, Multiple pressure chambers connected one-to-one to multiple supply channels, Multiple recovery channels connected separately to the aforementioned multiple pressure chambers, Multiple recovery manifolds for recovering the liquid from the multiple recovery channels, A flow path member having a recovery reservoir connected to the plurality of recovery manifolds for recovering the liquid from the plurality of recovery manifolds, An actuator configured to apply pressure to the liquid in the plurality of pressure chambers and to discharge droplets from a plurality of nozzles connected one-to-one to the plurality of pressure chambers, A pump configured such that the liquid flows sequentially through the supply reservoir, the plurality of supply manifolds, the plurality of supply channels, the plurality of pressure chambers, the plurality of recovery channels, the plurality of recovery manifolds, and the recovery reservoir, The system includes a controller configured to adjust the flow rate of the liquid to a predetermined target flow rate, Each of the aforementioned multiple pressure chambers is A pressure chamber body to which pressure is applied by the actuator, It has a descender connecting the pressure chamber body and the nozzle, The aforementioned recovery channel is connected to the descender, The aforementioned flow path has a flow path shape such that, when the flow rate is the target flow rate, the average viscosity of the liquid in the descender is 1.5 times or more the average viscosity of the liquid in the recovery flow path. Device.

2. The cross-sectional area of ​​the inlet surface of the supply channel or the recovery channel perpendicular to the flow direction of the liquid is S3, When S4 is the cross-sectional area of ​​the outlet surface of the descender that is perpendicular to the direction of liquid flow, S4 > S3 The apparatus according to claim 1.

3. Let S1 be the cross-sectional area of ​​the inlet surface of the nozzle perpendicular to the flow direction of the liquid. When S3 is the cross-sectional area of ​​the inlet surface of the supply channel or the recovery channel that is perpendicular to the flow direction of the liquid, S3 > S1 The apparatus according to claim 1 or 2.

4. The cross-sectional area of ​​the discharge surface of the nozzle perpendicular to the flow direction of the liquid is S2. When S3 is the cross-sectional area of ​​the inlet surface of the supply channel or the recovery channel that is perpendicular to the flow direction of the liquid, S3 > S2 The apparatus according to any one of claims 1 to 3.

5. The descender is Part 1 and, It has a second portion located closer to the pressure chamber body than the first portion, The flow path has a flow path shape such that, when the flow rate is the target flow rate, the average viscosity of the liquid in the second section is higher than the average viscosity of the liquid in the first section. The apparatus according to any one of claims 1 to 4.

6. A method using the apparatus described in any one of claims 1 to 5, The aforementioned liquid has a shear rate of 1000 s. －１ The viscosity at this point is 0.02 Pa·s or more and 0.4 Pa·s or less, and the shear rate is 0.01 s. －１ A pseudoplastic fluid with a viscosity of 0.5 Pa·s to 50 Pa·s is used. method.

7. The apparatus according to any one of claims 1 to 5, wherein the pump is a vacuum pump.

8. The apparatus according to any one of claims 1 to 5 and 7, wherein the target flow rate is 50 ml / min or more and 300 ml / min or less.

9. The cross-sectional area of ​​the inlet surface of the nozzle perpendicular to the direction of liquid flow is S1, When S2 is the cross-sectional area of ​​the discharge surface of the nozzle perpendicular to the direction of liquid flow, S1 > S2 The apparatus according to claim 3 or 4.

10. A method, The flow path member includes a supply reservoir, a plurality of supply manifolds connected to the supply reservoir, a plurality of supply channels connected to each of the plurality of supply manifolds (two or more), a plurality of pressure chambers connected one-to-one to the plurality of supply channels, a plurality of recovery channels connected separately to the plurality of pressure chambers, a plurality of recovery manifolds to which two or more of the plurality of recovery channels are each connected, and a recovery reservoir connected to the plurality of recovery manifolds, through which a pseudoplastic liquid is sequentially flowed. Pressurize the liquid in the plurality of pressure chambers and discharge droplets from a plurality of nozzles connected one-to-one to the plurality of pressure chambers. Each of the aforementioned multiple pressure chambers is The pressure chamber body to which pressure is applied by the actuator, and It has a descender that connects the pressure chamber body to the corresponding nozzle, The aforementioned recovery channel is connected to the descender, A method for adjusting the flow rate of the liquid such that the average viscosity of the liquid in the descender is 1.5 times or more the average viscosity of the liquid in the plurality of recovery channels.

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