Liquid dispensing device

Abstract

To provide a liquid discharge device configured so that the inside thereof can be prevented from being contaminated by mist, while eliminating the necessity for maintenance and being prevented from enlarging in size.SOLUTION: A liquid discharge device comprises a conveying part that conveys a medium along a conveyance passage in a conveying direction, and a liquid discharge part, arranged above the conveyance passage, which discharges liquid toward the medium conveyed by the conveying part. The liquid discharge part comprises a housing, a discharge head housed in the housing so that a nozzle for discharging liquid is exposed from a lower surface of the housing, and an air current generating part that generates air currents for making pressure inside the housing positive pressure. A slit through which air inside the housing is ejected as downward air currents toward the conveyance passage is formed on the lower surface of the housing.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a liquid ejection device.

Background Art

[0002] Conventionally, an inkjet printer including a conveyance unit that conveys a medium in a conveyance direction along a conveyance path and an ink ejection unit that is disposed above the conveyance path and ejects ink toward the medium conveyed by the conveyance unit is known.

[0003] In the inkjet printer having the above configuration, there is a problem that ink ejected from the ink ejection unit becomes atomized and floats, and adheres to the inside of the printer by riding on an air current, resulting in contamination inside the device. Therefore, as a technique for preventing contamination inside the device by mist, there is a technique of providing a mist recovery mechanism on the downstream side in the conveyance direction from the ink ejection unit (see, for example, Patent Document 1).

[0004] Further, in the inkjet printer having the above configuration, an air current due to conveyance of the medium hits ink droplets ejected from the ink ejection unit, thereby disturbing the air current between the ink ejection unit and the medium. Then, there is a problem that a curved white streak pattern (hereinafter referred to as "wind streak") is formed on the formed image due to the landing position of the ink droplets being disturbed. Therefore, as a technique for preventing the occurrence of wind streaks, there is a technique of generating an air current in the opposite direction to the conveyance direction on the upstream side in the conveyance direction from the ink ejection unit (see, for example, Patent Document 2).

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the technique of Patent Document 1, there is a problem that the recovered ink accumulates in the mist recovery mechanism, so that periodic maintenance of the mist recovery mechanism is required. Further, in the technique of Patent Document 2, since an air current generation mechanism is installed on the upstream side in the conveyance direction from the ink ejection unit, there is a problem that the inkjet printer becomes larger in the conveyance direction.

[0006] This invention was made to solve these problems, and aims to provide a technology for a liquid dispensing device that discharges liquid towards a medium that eliminates the need for maintenance, prevents the device from becoming large, and prevents contamination of the device by mist. [Means for solving the problem]

[0007] To solve the above problems, one aspect of the present invention provides a conveying unit that conveys a medium in the conveying direction along a conveying path, and a liquid dispensing unit that is positioned above the conveying path and dispenses liquid toward the medium conveyed by the conveying unit, wherein the liquid dispensing unit comprises a housing, a dispensing head housed in the housing such that a nozzle for dispensing liquid is exposed from the lower surface of the housing, and an airflow generating unit that generates an airflow to create positive pressure inside the housing, and a slit is formed on the lower surface of the housing to discharge the air inside the housing as a downward airflow toward the conveying path. The system further includes a controller that controls the direction of the airflow generated by the airflow generating unit, wherein the controller directs the airflow generated by the airflow generating unit toward the slit when the amount of liquid discharged from the nozzle toward the medium is greater than or equal to a threshold, and directs the airflow generated by the airflow generating unit toward a direction different from the slit when the amount of liquid discharged from the nozzle toward the medium is less than the threshold. It is characterized by the following: [Effects of the Invention]

[0008] According to the present invention, a liquid dispensing device that dispenses liquid towards a medium can be made maintenance-free, prevent increasing in size, and prevent contamination of the device by mist. [Brief explanation of the drawing]

[0009] [Figure 1] A diagram showing the overall configuration of an inkjet printer. [Figure 2] A diagram showing the external perspective view and internal structure of the line head. [Figure 3] This is a view of the line head from below. [Figure 4] Hardware configuration diagram of an inkjet printer. [Figure 5] Controller functional block diagram. [Figure 6] Flowchart of the airflow control process. [Figure 7] Flowchart for wind direction control processing. [Figure 8] Flowchart for aperture control processing. [Figure 9] A diagram showing other examples of nozzle and slit layouts. [Figure 10] A diagram showing yet another example of nozzle and slit layout. [Modes for carrying out the invention]

[0010] The inkjet printer 1 according to the present invention will be described below with reference to the drawings. Figure 1 is a diagram showing the overall configuration of the inkjet printer 1. The inkjet printer 1 is an example of a liquid ejection device (a device that ejects liquid) that forms an image on paper by ejecting ink, which is an example of a liquid, toward the paper. As shown in Figure 1, the inkjet printer 1 mainly comprises a transport unit 10, an ink ejection unit 20 (liquid ejection unit), a drying unit 30, and an image inspection unit 40.

[0011] The transport unit 10 transports a strip of continuous paper P (medium) along a transport path in the transport direction. More specifically, the transport unit 10 transports the continuous paper P along a transport path that goes from the unwinder 11 (described later) through the ink ejection unit 20, drying unit 30, and image inspection unit 40 to the rewinder 12. The transport unit 10 mainly comprises an unwinder 11, a rewinder 12, and a plurality of guide rollers 13.

[0012] The unwinder 11 has the continuous sheet of paper P wound around it before the image is formed. The unwinder 11 is supported by the frame of the inkjet printer 1 so as to be rotatable in the direction of unwinding the wound continuous sheet of paper P. The rewinder 12 has the continuous sheet of paper P wound around it after the image is formed. The rewinder 12 is supported by the frame of the inkjet printer 1 so as to be rotatable in the direction of winding up the continuous sheet of paper P with the image formed on it. Multiple guide rollers 13 are arranged between the unwinder 11 and the rewinder 12 at predetermined intervals in the transport direction. The guide rollers 13 rotate in contact with the continuous sheet of paper P being wound up by the rewinder 12, thereby guiding the continuous sheet of paper P and applying a predetermined tension to the continuous sheet of paper P.

[0013] The transport path is the space inside the inkjet printer 1 through which the continuous sheet of paper P passes. At least a portion of the transport path may be defined by an upper guide plate defining the upper end and a lower guide plate defining the lower end. The transport path is also formed in a curved or bent shape inside the inkjet printer 1. That is, the "transport direction" in this specification differs depending on the position of the transport path. However, the transport direction at the position facing the ink ejection unit 20 is the horizontal direction (the direction from right to left in Figure 1). In addition, among the directions along the surface of the continuous sheet of paper P, the direction perpendicular to the transport direction is referred to as the "width direction (main scanning direction)".

[0014] Furthermore, in this embodiment, a strip of continuous paper P is used as an example of a medium, but cut paper cut to a predetermined size (e.g., A4, B5, etc.) may also be used. In this case, the inkjet printer 1 may be equipped with a paper feed tray instead of an unwinder 11 and an output tray instead of a rewinder 12. Also, specific examples of materials to which liquid can adhere (mediums) are not limited to paper, but may also include OHP sheets, threads, fibers, fabrics, leather, metals, plastics, etc.

[0015] The ink ejection unit 20 is disposed on the downstream side in the conveyance direction from the unwinder 11 and on the upstream side in the conveyance direction from the drying unit 30. Also, the ink ejection unit 20 is disposed facing the conveyance path above the portion of the conveyance path that extends in the horizontal direction. The ink ejection unit 20 includes a plurality of line heads 21B, 21C, 21M, 21Y that eject inks of different colors (black, cyan, magenta, yellow). The plurality of line heads 21B, 21C, 21M, 21Y are arranged in the conveyance direction. Since the line heads 21B, 21C, 21M, 21Y have the same configuration except for the color of the ejected ink, they may hereinafter be collectively referred to as "line head 21". The configuration of the line head 21 will be described later with reference to FIGS. 2 and 3.

[0016] The drying unit 30 is disposed on the downstream side in the conveyance direction from the ink ejection unit 20 and on the upstream side in the conveyance direction from the image inspection unit 40. The drying unit 30 dries the ink attached to the continuous form paper P. The drying unit 30 may be, for example, a heater that contacts and heats the continuous form paper P or a blower that supplies warm air toward the continuous form paper P. However, the drying unit 30 may be omitted.

[0017] The image inspection unit 40 is disposed facing the conveyance path on the downstream side in the conveyance direction from the drying unit 30 and on the upstream side in the conveyance direction from the rewinder 12. The image inspection unit 40 inspects whether an image is appropriately formed on the continuous form paper P. The image inspection unit 40 is, for example, a camera that photographs the surface of the continuous form paper P. However, the image inspection unit 40 may be omitted.

[0018] FIG. 2 is a diagram showing an external perspective view and an internal structure of the line head 21. FIG. 3 is a diagram of the line head 21 viewed from the bottom side. As shown in FIGS. 2 and 3, the line head 21 mainly includes a housing 22, a plurality of ejection heads 23A, 23B, 23D, 23E, 23F, 23G that are each unitized (hereinafter, these may be collectively referred to as "ejection head 23"), and a plurality of fans 24A, 24B, 24C (hereinafter, these may be collectively referred to as "fan 24").

[0019] The housing 22 has an outer shape generally in the form of a rectangular parallelepiped. That is, the housing 22 includes an upper surface 22A, a lower surface 22B, and four side surfaces 22C, 22D, 22E, and 22F disposed between the upper surface 22A and the lower surface 22B. The upper surface 22A and the lower surface 22B face each other in the vertical direction. The side surfaces 22C and 22D face each other in the conveyance direction. The side surfaces 22E and 22F face each other in the width direction. And the housing 22 is box-shaped with an internal space defined by the upper surface 22A, the lower surface 22B, and the side surfaces 22C to 22F.

[0020] The ejection head 23 includes a plurality of nozzles N that eject ink supplied through an ink supply port 25 and a flow path member 26 shown in FIG. 2(A) onto the continuous form P on the conveyance path. Also, as shown in FIG. 2(B), the ejection head 23 is housed in the internal space of the housing 22. Further, as shown in FIG. 3, the nozzles N of the ejection head 23 are exposed from the lower surface 22B of the housing 22. That is, the nozzles N are arranged to face the conveyance path above the conveyance path. Furthermore, the plurality of nozzles N are arranged at predetermined intervals in the conveyance direction and the width direction.

[0021] The ejection heads 23A, 23B, 23C, and 23D are arranged in a row at predetermined intervals in the width direction. Similarly, the ejection heads 23E, 23F, and 23G are arranged in a row at predetermined intervals in the width direction. Also, the ejection heads 23E to 23G are arranged between the adjacent ejection heads 23A to 23D and on the downstream side in the conveyance direction from the ejection heads 23A to 23D. In other words, the ejection heads 23A to 23G are arranged in a staggered pattern along the lower surface 22B of the housing 22. The ejection heads 23A, 23B, 23C, and 23D are an example of the first ejection head, and the ejection heads 23E, 23F, and 23G are an example of the second ejection head.

[0022] The fan 24 is mounted on the upper surface 22A of the housing 22. That is, the fan 24 is positioned directly above the discharge head 23. In other words, when the line head 21 is viewed from above and below, the fan 24 is positioned so as to overlap the discharge head 23. The fan 24 is configured to adjust the airflow volume it generates according to the control of the controller 100 (for example, the magnitude of the supplied current), which will be described later. The fan 24 is an example of an airflow generating unit that generates airflow inside the housing 22. However, the specific example of an airflow generating unit is not limited to the fan 24; a blower or the like may also be used.

[0023] Fans 24A and 24C are examples of positive pressure generating units that generate airflow in a direction that creates positive pressure inside the housing 22 (i.e., supply air to the inside of the housing 22). Fan 24B is an example of a negative pressure generating unit that generates airflow in a direction that creates negative pressure inside the housing 22 (i.e., expels air from the inside of the housing 22). To make fan 24B function as a negative pressure generating unit, for example, fans 24A and 24C can be reversed and fan 24B can be mounted on the top surface 22A.

[0024] In this embodiment, fans 24A and 24C are arranged at two locations spaced apart in the width direction. Fan 24B is arranged between fans 24A and 24C in the width direction. In other words, positive pressure generating units and negative pressure generating units are alternately arranged in the width direction of the line head 21. Furthermore, the number of positive pressure generating units is greater than the number of negative pressure generating units. As a result, the internal space of the housing 22 is maintained at positive pressure. However, the method for maintaining positive pressure in the internal space of the housing 22 is not limited to the difference in the number of positive pressure generating units and negative pressure generating units; it is sufficient to make the airflow generated by the positive pressure generating units greater than the airflow generated by the negative pressure generating units.

[0025] Furthermore, as shown by the dashed lines in Figure 3(A), slits 27A, 27B, 27C, 27D, 27E, 27F, and 27G (hereinafter collectively referred to as "slit 27") are formed on the lower surface 22B of the housing 22. The slits 27 penetrate the lower surface 22B in the thickness direction. In other words, the air in the internal space of the housing 22 is discharged downward through the slits 27. To put it another way, the slits 27 discharge the air in the internal space of the housing 22, which is maintained at positive pressure, as a downward airflow toward the transport path.

[0026] The slits 27A to 27G in this embodiment are formed to surround the multiple nozzles N provided by each of the multiple discharge heads 23A to 23G. In other words, the slits 27A to 27G in this embodiment are formed in a frame shape that is continuous in the circumferential direction. However, the layout of the slits 27 is not limited to the example in Figure 3.

[0027] The line head 21 also includes a plate-shaped louver 28 (see Figure 4). The louver 28 is housed in the internal space of the housing 22 at a position facing the fans 24A and 24C, respectively. The louver 28 adjusts (changes) the direction of the airflow generated by the fans 24A and 24C according to the control of the controller 100. The louver 28 is an example of an airflow direction adjustment unit. However, the method of adjusting the direction of the airflow generated by the fans 24A and 24C is not limited to the louver 28; the fans 24A and 24C themselves may be configured to change direction.

[0028] Furthermore, the line head 21 is equipped with a sliding plate 29 (see Figure 4). The sliding plate 29 adjusts (increases or decreases) the opening amount of the slit 27 by sliding along the lower surface 22B of the housing 22 according to the control of the controller 100. The sliding plate 29 is an example of an opening amount adjustment unit. However, the specific method for adjusting the opening amount of the slit 27 is not limited to the sliding plate 29.

[0029] Figure 4 is a hardware configuration diagram of inkjet printer 1. As shown in Figure 4, inkjet printer 1 has a configuration in which a CPU (Central Processing Unit) 101, RAM (Random Access Memory) 102, ROM (Read Only Memory) 103, HDD (Hard Disk Drive) 104, and I / F 105 are connected via a common bus 109.

[0030] The CPU 101 is the processing unit and controls the overall operation of the inkjet printer 1. The RAM 102 is a volatile storage medium that allows for high-speed reading and writing of information and is used as a workspace for the CPU 101 when processing information. The ROM 103 is a read-only, non-volatile storage medium that stores programs such as firmware. The HDD 104 is a non-volatile storage medium that allows for reading and writing of information and has a large storage capacity, and stores the OS (Operating System), various control programs, application programs, etc.

[0031] The inkjet printer 1 processes control programs stored in ROM 103 and information processing programs (application programs) loaded into RAM 102 from storage media such as HDD 104 using the arithmetic functions of the CPU 101. This processing constitutes a software control unit that includes various functional modules of the inkjet printer 1. The combination of this software control unit and the hardware resources installed in the inkjet printer 1 constitutes a functional block that realizes the functions of the inkjet printer 1. In other words, the CPU 101, RAM 102, ROM 103, HDD 104, and I / F 105 constitute a controller 100 that controls the operation of the inkjet printer 1.

[0032] I / F105 is an interface that connects the transport unit 10, ink ejection unit 20, drying unit 30, image inspection unit 40, fan 24, louvers 28, slide plate 29, and operation panel 110 to the common bus 109. The controller 100 operates the transport unit 10, ink ejection unit 20, drying unit 30, image inspection unit 40, fan 24, louvers 28, and slide plate 29 through I / F105.

[0033] The control panel 110 comprises an operation unit that receives user input and a display (notification unit) that provides information to the user. The operation unit includes, for example, hard keys, a touch panel superimposed on the display, etc. The control panel 110 acquires information from the user through the operation unit and provides information to the user through the display. The notification unit is not limited to a display and may also include LED lamps, speakers, etc.

[0034] Figure 5 is a functional block diagram of the controller 100. The controller 100 mainly comprises a speed control unit 111, a discharge control unit 112, a temperature control unit 113, an inspection control unit 114, an airflow control unit 115, an airflow direction control unit 116, and an opening amount control unit 117. Each functional block 111 to 117 is realized by the CPU 101 executing a program stored in the ROM 103 or HDD 104.

[0035] The controller 100 forms an image on the continuous sheet of paper P in response to receiving an image formation instruction. The image formation instruction includes at least image data indicating the image to be formed on the continuous sheet of paper P. The image formation instruction may be obtained, for example, from the user through the operation panel 110, or from an external device through a communication network. The controller 100 then calculates the print rate based on the image data included in the image formation instruction. The print rate refers to the amount of liquid discharged from the nozzle N toward the continuous sheet of paper P. More specifically, the print rate refers to the amount of ink discharged per unit area of ​​the continuous sheet of paper P.

[0036] The speed control unit 111 controls the transport speed of the continuous paper P by the transport unit 10. For example, the speed control unit 111 should slow down the transport speed of the continuous paper P as the print density increases. The speed control unit 111 controls the transport speed by adjusting the magnitude of the current supplied to the motor that rotates the rewinder 12, for example. The ejection control unit 112 ejects ink from the line heads 21B, 21C, 21M, and 21Y at predetermined timings so that the image instructed by the image formation instruction is formed on the continuous paper P. For example, the ejection control unit 112 ejects ink from the nozzles N by applying a voltage at predetermined timings to the piezoelectric elements mounted on the ejection head 23 corresponding to each nozzle N.

[0037] The temperature control unit 113 controls the temperature of the drying unit 30. For example, the temperature control unit 113 should raise the temperature of the drying unit 30 as the printing density increases. The inspection control unit 114 determines whether an appropriate image has been formed on the continuous paper P based on the image captured by the image inspection unit 40. If the inspection control unit 114 determines that an appropriate image has not been formed, it may notify the operator of the error through the operation panel 110, or it may correct the image formed on the continuous paper P thereafter.

[0038] The airflow control unit 115 controls the airflow generated by the fan 24, for example, by adjusting the magnitude of the current supplied to the fan 24. Airflow refers to the amount of airflow generated by the fan 24 per unit time. Details of the processing of the airflow control unit 115 will be described later with reference to Figure 6. The airflow direction control unit 116 controls the direction of the airflow generated by the fan 24, for example, by rotating the louvers 28. Details of the processing of the airflow direction control unit 116 will be described later with reference to Figure 7. The opening amount control unit 117 controls the opening amount of the slit 27, for example, by sliding the slide plate 29. Details of the processing of the opening amount control unit 117 will be described later with reference to Figure 8.

[0039] First, the temperature control unit 113 controls the drying unit 30 to reach the desired temperature in response to receiving an image formation instruction. Next, the speed control unit 111 starts transporting the continuous sheet paper P at a predetermined speed in response to the drying unit 30 reaching the desired temperature. Next, the discharge control unit 112 discharges ink from the ink discharge unit 20 at a predetermined timing toward the continuous sheet paper P being transported by the transport unit 10. As a result, the image instructed by the image formation instruction is formed on the continuous sheet paper P. The inspection control unit 114 also inspects the image formed on the continuous sheet paper P. Furthermore, the airflow control unit 115, the airflow direction control unit 116, and the aperture amount control unit 117 perform the processes shown in Figures 6 to 8 from the time the image formation instruction is received until the image formation on the continuous sheet paper P is completed.

[0040] Figure 6 is a flowchart of the airflow control process. The airflow control unit 115 compares the print density with a predetermined threshold (S601). If the print density is greater than or equal to the threshold (S601: Yes), the airflow control unit 115 sets the airflow of the fan 24 to "strong (first airflow)" (S602). On the other hand, if the print density is less than the threshold (S601: No), the airflow control unit 115 sets the airflow of the fan 24 to "weak (second airflow)" (S603). The second airflow is less than the first airflow. The airflow control unit 115 then rotates the fan 24 to generate an airflow of the airflow set in steps S602 and S603.

[0041] The airflow control unit 115 generates an airflow in the fan 24 with an airflow volume corresponding to the printing rate by repeating the process in steps S601 to S603 until printing on the continuous form paper P is completed (S604: No). Furthermore, the airflow control unit 115 stops the fan 24 (S605) in response to the completion of printing on the continuous form paper P (S604: Yes).

[0042] Figure 7 is a flowchart of the wind direction control process. The wind direction control unit 116 compares the print density with a predetermined threshold (S701). If the print density is greater than or equal to the threshold (S701:Yes), the airflow control unit 115 directs the airflow generated by the fan 24 towards the slit 27 (S702). On the other hand, if the print density is less than the threshold (S701:No), the wind direction control unit 116 directs the airflow generated by the fan 24 in a direction different from the slit 27 (S703). The wind direction control unit 116 then repeats the process from steps S701 to S703 until printing on the continuous paper P is completed (S704:No), adjusting the direction of the louvers 28 so that the airflow is directed in the direction set in steps S702 and S703. Furthermore, the wind direction control unit 116 terminates control of the louvers 28 in response to the completion of printing on the continuous paper P (S704:Yes) (S705).

[0043] Figure 8 is a flowchart of the aperture amount control process. The aperture amount control unit 117 compares the print rate with a predetermined threshold (S801). If the print rate is greater than or equal to the threshold (S801: Yes), the aperture amount control unit 117 sets the aperture amount of the slit 27 to "large (first aperture amount)" (S802). On the other hand, if the print rate is less than the threshold (S801: No), the aperture amount control unit 117 sets the aperture amount of the slit 27 to "small (second aperture amount)" (S803). Then, the aperture amount control unit 117 controls the position of the slide plate 29 to achieve the aperture amount set in steps S802 and S803 by repeating the process in steps S801 to S803 until printing on the continuous form paper P is completed (S804: No). Furthermore, the aperture amount control unit 117 terminates control of the slide plate 29 in response to the completion of printing on the continuous form paper P (S804: Yes) (S805).

[0044] Furthermore, the airflow direction control unit 116 may, for example, in step S702, direct the airflow to the portion of the slit 27 surrounding the second discharge heads 23E, 23F, and 23G that extends in the width direction upstream of the nozzle N, as shown by the thick solid line in Figure 3(B). Also, the opening amount control unit 117 may, for example, in steps S802 and S803, control the opening amount of the portion of the slit 27 surrounding the second discharge heads 23E, 23F, and 23G that extends in the width direction upstream of the nozzle N, as shown by the thick solid line in Figure 3(B).

[0045] Furthermore, when the controller 100 calculates the overall print density of the image formed on the continuous sheet of paper P, the airflow rate set in steps S602 and S603 in Figure 6, the airflow direction set in steps S702 and S703 in Figure 7, and the aperture amount set in steps S802 and S803 in Figure 8 remain constant from the start to the end of image formation on the continuous sheet of paper P. Alternatively, the controller 100 may divide the image formed on the continuous sheet of paper P in the transport direction and calculate the print density of each divided portion image. In this case, the airflow rate set in steps S602 and S603 in Figure 6, the airflow direction set in steps S702 and S703 in Figure 7, and the aperture amount set in steps S802 and S803 in Figure 8 change constantly from the start to the end of image formation on the continuous sheet of paper P.

[0046] According to the above embodiment, for example, the following effects are achieved.

[0047] According to the above embodiment, the airflow generated by the fan 24 attached to the housing 22 is supplied to the transport path as a downward airflow through a slit 27 formed on the lower surface 22B of the housing 22. This allows the ink ejected from the discharge head 23 to land on the continuous sheet paper P before it is atomized. As a result, maintenance is unnecessary, the size of the device is prevented, and contamination of the device by mist can be prevented. Furthermore, according to this embodiment, the generation of wind ripples can also be prevented.

[0048] Furthermore, according to the above embodiment, a fan 24 is provided directly above the discharge heads 23A to 23G. This prevents an increase in the size of the ink discharge section 20 in the transport direction. Also, according to the above embodiment, slits 27 are formed to surround each of the discharge heads 23A to 23G. This makes it possible to equalize the misting prevention effect for each of the discharge heads 23A to 23G.

[0049] Furthermore, according to the above embodiment, fans 24A and 24C function as positive pressure generators, and fan 24B functions as a negative pressure generator. This allows the air inside the housing 22 to be circulated while maintaining positive pressure inside the housing 22. This enables efficient cooling of the discharge heads 23A to 23G.

[0050] Furthermore, according to the above embodiment, the airflow (Figure 6), airflow direction (Figure 7), and opening size (Figure 8) are changed according to the printing rate. This allows for the suppression of mist generation by increasing the downward airflow when a large amount of ink is ejected from the nozzle N. Conversely, when a small amount of ink is ejected from the nozzle N, the downward airflow is weakened to suppress misalignment of ink on the continuous paper P. The controller 100 may execute all of the processes shown in Figures 6, 7, and 8 in parallel, or it may execute only some of them.

[0051] Wind ripples are particularly likely to occur at the location indicated by the thick solid line in Figure 3(B) (i.e., the location upstream of the second discharge heads 23E to 23G in the conveying direction). Therefore, according to the above embodiment, wind ripples can be efficiently prevented by centrally controlling this portion in the wind direction control process and the aperture amount control process.

[0052] Furthermore, as the continuous sheet of paper P moves, an airflow (hereinafter referred to as "conveyor airflow") is generated within the conveyor path that flows in the conveying direction. By providing a slit 27 upstream of the nozzle N in the conveying direction to generate a downward airflow, the amount of conveyor airflow reaching the nozzle N in the conveying direction can be reduced. This prevents the ink discharged from the nozzle N from becoming a mist and prevents misalignment of the ink on the continuous sheet of paper P.

[0053] [Differentiation] Note that the layout of the nozzle N and slit 27 on the lower surface 22B of the housing 22 is not limited to the example in Figure 3. Therefore, other examples of the layout of the nozzle N and slit 27 will be described with reference to Figures 9 and 10. Figure 9 is a diagram showing another example of the layout of the nozzle N and slit 27. Figure 10 is a diagram showing yet another example of the layout of the nozzle N and slit 27. Below, a detailed explanation of the commonalities with the above embodiment will be omitted, and the differences will be the focus of the explanation.

[0054] First, as shown in Figure 3, the discharge heads 23A to 23G do not necessarily have to be arranged in a staggered pattern. As another example, as shown in Figure 9(A), multiple discharge heads 23A to 23C may be arranged in a single row in the width direction on the lower surface 22B of the housing 22. Note that the number of discharge heads 23A to 23C in the example of Figure 9(A) is not limited to three.

[0055] Furthermore, as shown in Figures 2(B) and 3, the line head 21 does not necessarily have to be equipped with multiple discharge heads 23A to 23G, each of which is a unitized unit. As another example, as shown in Figures 9(B) to 9(D), all nozzles N exposed on the lower surface 22B of the housing 22 may be controlled by a single discharge head 23. In this case, the row of multiple nozzles N arranged in a line in the width direction (hereinafter referred to as "nozzle row") may be a single row as shown in Figure 9(B), or there may be multiple rows in the transport direction as shown in Figures 9(C) and 9(D). Furthermore, as shown in Figure 9(D), adjacent nozzle rows in the transport direction may be offset in the width direction.

[0056] Furthermore, as shown in Figure 3, the slit 27 does not have to be formed to surround each of the multiple discharge heads 23A to 23G. As another example, as shown by the thick solid line in Figure 9, the slit 27 may be a single frame shape surrounding all the nozzles N formed on the lower surface 22B of the housing 22. In other words, the slit 27 may be formed along the outer circumference of the lower surface 22B of the housing 22 so as to surround multiple nozzles N.

[0057] Furthermore, as shown in Figures 3 and 9, the slit 27 does not have to be a continuous frame shape in the circumferential direction. As another example, as shown by the thick solid line in Figure 10(A), the slit 27 may be formed on the edges extending in the width direction on both the upstream and downstream sides of the nozzle N in the transport direction, within the outer periphery of the lower surface 22B of the housing 22. In addition to the arrangement in Figure 10(A), as shown by the thick solid line in Figure 10(B), the slit 27 may be formed on at least a portion of the edges extending in the transport direction on both sides of the nozzle N in the width direction. More specifically, as shown by the thick solid line in Figure 10(C), if mounting parts 50 for attaching the ink ejection unit 20 to the frame of the inkjet printer 1 are provided at both ends of the housing 22 in the width direction, the slit 27 may be provided at a different position from the mounting parts 50 on the edges extending in the transport direction on both sides of the nozzle N in the width direction.

[0058] As another example shown in Figure 6, the airflow control unit 115 may compare the transport speed of the transport unit 10 with a predetermined threshold in step S601. Then, if the transport speed is greater than or equal to the threshold (S601: Yes), the airflow control unit 115 may set the airflow of the fan 24 to "strong (first airflow)" (S602). On the other hand, if the transport speed is less than the threshold (S601: No), the airflow control unit 115 may set the airflow of the fan 24 to "weak (second airflow)" (S603).

[0059] As another example shown in Figure 7, the fan 24 may be mounted on the housing 22 so that the airflow it generates is always directed towards the slit 27. As yet another example, the louvers 28 may be fixed so that the airflow generated by the fan 24 is always directed towards the slit 27.

[0060] Furthermore, the above embodiments and modifications describe an example of a so-called "line head printer" in which a plurality of nozzles N are arranged on the lower surface 22B of the housing 22 in the width direction so as to face the entire area of ​​the continuous sheet of paper P. However, the present invention can be applied not only to line head printers but also to "serial head printers" of the type in which the carriage equipped with the ejection head moves in the width direction (main scanning direction).

[0061] This "liquid dispensing device" may also include means for feeding, transporting, and dispensing paper onto materials to which liquid can adhere, as well as pre-treatment devices, post-treatment devices, etc.

[0062] For example, "devices that dispense liquids" include image forming machines, which dispense ink to form images on paper, and three-dimensional molding machines, which dispense molding liquid into a powder layer formed in layers to create three-dimensional objects.

[0063] Furthermore, the term "liquid dispensing device" is not limited to devices that visualize meaningful images such as letters or figures through the dispensed liquid. For example, it also includes devices that form patterns that do not have meaning in themselves, or devices that create three-dimensional images.

[0064] The term "materials to which liquid can adhere" above refers to materials to which liquid can adhere, at least temporarily, including materials that adhere and solidify, or materials that adhere and penetrate. Specific examples include recording media such as paper, recording paper, film, and cloth; electronic components such as electronic circuit boards and piezoelectric elements; powder layers; organ models; and inspection cells. Unless otherwise specified, it includes all materials to which liquid can adhere.

[0065] The materials referred to as "materials to which liquid can adhere" above include paper, thread, fibers, fabrics, leather, metal, plastic, glass, wood, ceramics, etc., as long as liquid can adhere to them, even temporarily.

[0066] Furthermore, the "liquid" is not particularly limited, as long as it has the viscosity and surface tension to be dispensed from the head, but it is preferable that its viscosity becomes 30 mPa·s or less at room temperature and atmospheric pressure, or when heated or cooled. More specifically, it is a solution, suspension, emulsion, etc. containing a solvent such as water or an organic solvent, a colorant such as a dye or pigment, a polymerizable compound, a resin, a functional material such as a surfactant, a biocompatible material such as DNA, amino acids or proteins, calcium, or an edible material such as a natural pigment. These can be used, for example, as inkjet inks, surface treatment liquids, liquids for forming components of electronic elements and light-emitting elements or electronic circuit resist patterns, and material liquids for 3D molding.

[0067] Furthermore, "liquid dispensing devices" include devices in which the liquid dispensing head and the surface to which the liquid can adhere move relative to each other, but are not limited to these. Specific examples include serial-type devices in which the liquid dispensing head moves, and line-type devices in which the liquid dispensing head does not move.

[0068] Other examples of "devices that dispense liquids" include processing liquid coating devices that dispense processing liquid onto the surface of paper for purposes such as modifying the surface of the paper, and injection granulation devices that granulate fine particles of raw materials by spraying a composition liquid, in which raw materials are dispersed in a solution, through a nozzle N.

[0069] Furthermore, the control method described above may be implemented, for example, by a program. That is, the control method is a method by which a computer executes by having the arithmetic unit, memory device, input device, output device, and control device work together based on a program. The program may also be written to a memory device or storage medium and distributed, or distributed via telecommunication lines, etc.

[0070] Furthermore, the portion of each function of the embodiment described above that is executed by the controller 100 can be implemented by one or more processing circuits. Hereinafter, "processing circuit" in this specification includes processors programmed to execute each function by software, such as processors implemented by electronic circuits, and devices such as ASICs (Application Specific Integrated Circuits), DSPs (digital signal processors), FPGAs (field programmable gate arrays), and conventional circuit modules designed to execute each of the functions described above.

[0071] It should be noted that the present invention is not limited to the embodiments exemplified above, and various modifications are possible without departing from its technical essence. All technical matters included in the technical concept described in the claims are covered by the present invention. The above embodiments are preferred examples, but those skilled in the art can realize various modifications from the disclosed content. Such modifications are also included in the technical scope described in the claims.

[0072] [Aspects of the present invention] The contents of this invention are, for example, as follows: <1> A conveying unit that conveys the medium in the conveying direction along the conveying path, It comprises a liquid discharge unit positioned above the transport path and discharging liquid toward the medium transported by the transport unit, The aforementioned liquid dispensing unit is The casing and A discharge head housed in the housing is provided such that a nozzle for discharging liquid is exposed from the lower surface of the housing, The enclosure is equipped with an airflow generating unit that generates an airflow to create a positive pressure inside the enclosure, The liquid dispensing device is characterized in that a slit is formed on the lower surface of the housing, which discharges the air inside the housing as a downward airflow toward the transport path.

[0073] <2> The slit is formed on the outer periphery of the lower surface of the housing, on the upstream and downstream sides of the nozzle in the conveying direction, and on the sides extending in the width direction perpendicular to the conveying direction. <1> This is the liquid dispensing device described in [reference].

[0074] <3> The slit is formed on at least a portion of the edges extending in the transport direction on both sides of the nozzle in the width direction, within the outer periphery of the lower surface of the housing. <2> This is the liquid dispensing device described in [reference].

[0075] <4> The liquid discharge unit is characterized by comprising an opening amount adjustment unit for adjusting the opening amount of the slit. <1> from <3> It is a liquid dispensing device as described in any one of the following.

[0076] <5> The airflow generating unit is characterized in that it is housed inside the housing directly above the discharge head. <1> From the above <4> It is a liquid dispensing device as described in any one of the following.

[0077] <6> The aforementioned airflow generating unit is A positive pressure generating unit that generates an airflow in a direction that creates positive pressure inside the housing, The aforementioned housing is characterized by comprising a negative pressure generating unit that generates an airflow in a direction that creates negative pressure inside the housing. <1> From the above <5> It is a liquid dispensing device as described in any one of the following.

[0078] <7> The positive pressure generating units are arranged at two locations spaced apart in the width direction perpendicular to the conveying direction. The negative pressure generating unit is characterized in that it is arranged between the two positive pressure generating units in the width direction. <6> This is the liquid dispensing device described in [reference].

[0079] <8> The liquid dispensing unit comprises a plurality of dispensing heads, each of which is a unitized unit. Multiple of the aforementioned discharge heads are A plurality of first discharge heads are arranged spaced apart in the width direction perpendicular to the conveying direction, It includes a plurality of second discharge heads arranged between adjacent first discharge heads and downstream of the first discharge heads in the conveying direction, spaced apart in the width direction, The slit is formed so as to surround the nozzle of each of the multiple discharge heads. <1> From the above <7> It is a liquid dispensing device as described in any one of the following.

[0080] <9> The system includes a controller that controls the strength of the airflow generated by the aforementioned airflow generating unit. The aforementioned controller, When the amount of liquid discharged from the nozzle toward the medium is greater than or equal to a threshold, the airflow generating unit generates an airflow of a first volume. The characteristic feature is that when the amount of liquid discharged from the nozzle toward the medium is less than the threshold, the airflow generating unit generates an airflow of a second airflow volume which is less than the first airflow volume. <1> From the above <8> It is a liquid dispensing device as described in any one of the following.

[0081] <10> The system includes a controller that controls the strength of the airflow generated by the aforementioned airflow generating unit. The aforementioned controller, When the transport speed by the transport unit is equal to or greater than a threshold, the airflow generation unit generates an airflow of the first volume. The characteristic feature is that when the transport speed by the transport unit is less than the threshold, the airflow generating unit generates an airflow of a second airflow volume less than the first airflow volume. <1> From the above <9> It is a liquid dispensing device as described in any one of the following.

[0082] <11> The system includes a controller that controls the direction of the airflow generated by the aforementioned airflow generating unit. The aforementioned controller, When the amount of liquid discharged from the nozzle toward the medium exceeds a threshold, the airflow generated by the airflow generating unit is directed toward the slit. The airflow generated by the airflow generating unit is directed in a direction different from the slit when the amount of liquid discharged from the nozzle toward the medium is less than the threshold. <1> From the above <10> It is a liquid dispensing device as described in any one of the following.

[0083] <12> The airflow generating unit is mounted on the housing such that the generated airflow is always directed towards the slit. <1> From the above <10> A liquid dispensing device as described in any one of the following.

[0084] <13> The system includes a controller for controlling the aperture adjustment unit, The aforementioned controller, When the amount of liquid discharged from the nozzle toward the medium exceeds a threshold, the opening amount adjustment unit adjusts the opening amount of the slit to a first opening amount. The characteristic feature is that when the amount of liquid discharged from the nozzle toward the medium is less than the threshold, the opening amount adjustment unit adjusts the opening amount of the slit to a second opening amount that is smaller than the first opening amount. <4> This is the liquid dispensing device described in [reference].

[0085] <14> The lower surface of the housing is characterized in that a plurality of nozzles are arranged in a width direction perpendicular to the conveying direction so as to face the entire area of ​​the medium conveyed by the conveying unit. <1> From the above <13> It is a liquid dispensing device as described in any one of the following. [Explanation of Symbols]

[0086] 1: Inkjet printer 10: Conveying section 11: Unwinder 12: Rewinder 13: Guide roller 20: Ink ejection section 21B, 21C, 21M, 21Y: Line head 22: Cabinet 22A:Top surface 22B: Bottom surface 22C, 22D, 22E, 22F: Side 23A, 23B, 23C, 23D, 23E, 23F, 23G: Discharge head 24A, 24B, 24C: Fan 25: Ink supply port 26: Flow channel member 27A, 27B, 27C, 27D, 27E, 27F, 27G: Slit 28: Luba 29: Sliding plate 30:Drying section 40: Image Inspection Department 50: Mounting part 100: Controller 101: CPU 102: RAM 103: ROM 104: HDD 105 :I / F 109: Common Bus 110: Control Panel 111: Speed ​​control unit 112: Discharge control unit 113: Temperature Control Unit 114: Inspection Control Unit 115: Airflow control unit 116: Wind Direction Control Unit 117: Aperture control unit [Prior art documents] [Patent Documents]

[0087] [Patent Document 1] Japanese Patent Publication No. 2017-213712 [Patent Document 2] Japanese Patent Publication No. 2010-179626

Claims

1. A conveying unit that conveys the medium in the conveying direction along the conveying path, It comprises a liquid discharge unit positioned above the transport path and discharging liquid toward the medium transported by the transport unit, The aforementioned liquid dispensing unit is The casing and A discharge head housed in the housing is provided such that a nozzle for discharging liquid is exposed from the lower surface of the housing, The enclosure is equipped with an airflow generating unit that generates an airflow to create a positive pressure inside the enclosure, A slit is formed on the lower surface of the housing to discharge the air inside the housing as a downward airflow toward the transport path. The system further includes a controller that controls the direction of the airflow generated by the airflow generating unit, The aforementioned controller, When the amount of liquid discharged from the nozzle toward the medium exceeds a threshold, the airflow generated by the airflow generating unit is directed toward the slit. A liquid dispensing device characterized in that, when the amount of liquid discharged from the nozzle toward the medium is less than the threshold, the airflow generated by the airflow generating unit is directed in a direction different from the slit.

2. The liquid dispensing device according to claim 1, characterized in that the slit is formed on an edge extending in a width direction perpendicular to the conveying direction, both upstream and downstream of the nozzle in the conveying direction, within the outer periphery of the lower surface of the housing.

3. The liquid dispensing device according to claim 2, characterized in that the slit is formed on at least a portion of the edges extending in the transport direction on both sides of the nozzle in the width direction, within the outer periphery of the lower surface of the housing.

4. The liquid dispensing device according to claim 1, characterized in that the liquid dispensing unit is provided with an opening amount adjustment unit for adjusting the opening amount of the slit.

5. The liquid dispensing device according to claim 1, characterized in that the airflow generating unit is housed inside the housing directly above the dispensing head.

6. The aforementioned airflow generating unit is A positive pressure generating unit that generates an airflow in a direction that creates positive pressure inside the housing, The liquid dispensing device according to claim 1, further comprising a negative pressure generating unit that generates an airflow in a direction that creates a negative pressure inside the housing.

7. The positive pressure generating units are arranged at two locations spaced apart in the width direction perpendicular to the conveying direction. The liquid dispensing device according to claim 6, characterized in that the negative pressure generating unit is arranged between two positive pressure generating units in the width direction.

8. The liquid dispensing unit comprises a plurality of dispensing heads, each of which is a unitized unit. Multiple of the aforementioned discharge heads are A plurality of first discharge heads are arranged spaced apart in the width direction perpendicular to the conveying direction, It includes a plurality of second discharge heads arranged between adjacent first discharge heads and downstream of the first discharge heads in the conveying direction, spaced apart in the width direction, The liquid dispensing device according to claim 1, characterized in that the slit is formed so as to surround the nozzle of each of the plurality of dispensing heads.

9. The liquid dispensing device according to claim 1, characterized in that the airflow generating unit is attached to the housing such that the generated airflow is always directed toward the slit.

10. The liquid dispensing device according to claim 1, characterized in that a plurality of nozzles are arranged on the lower surface of the housing in a width direction perpendicular to the conveying direction so as to face the entire area of ​​the medium conveyed by the conveying unit.

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