Droplet ejection device

Abstract

To provide a droplet discharge device which can highly accurately determine discharge bending of droplets in comparison to a conventional technique.SOLUTION: A droplet discharge device comprises: a first light source which emits first light toward a flying space to which droplets discharged from a nozzle fly; a second light source which is provided at a position different from the first light source and emits second light in the direction intersecting the first light toward the flying space; two movement devices which move the first light source and the second light source independently such that the emission directions or emission positions of the first light and second light change; a first detection element which detects the first light; a second detection element which detects the second light; and a control device. The control device calculates a discharge bend amount to the normal flying direction of the droplets on the basis of the first light reception amount about the first light detected by the first detection element and the second light reception amount about the second light detected by the second detection element when the first light is emitted from the first light source and the second light is emitted from the second light source.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a droplet ejection device used in an image recording apparatus such as an inkjet printer.

Background Art

[0002] [[ID=ll]] Conventionally, there is a technique for detecting the ejection curve of ink droplets ejected from an ejection head. The ink droplets ejected from the ejection head include ink droplets flying along a normal ejection path, ink droplets flying along an ejection path having an allowable curve, and ink droplets flying along an abnormal ejection path. For example, Patent Document 1 discloses rotating an optical element around the optical axis of a beam of light to rotate a sheet-like beam of light around the optical axis. By rotating the beam of light in this way, the beam of light can intersect each of the ink droplets flying along the various ejection paths ejected from the ejection head. By receiving the reflected light generated by this intersection with a light receiving element, it is possible to determine the ejection curve of the ink droplet based on the intensity of the received reflected light.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, since the ink droplets ejected from the ejection head include ink droplets flying in various directions, it has been difficult to accurately determine the ejection curve of the ink droplets with the above conventional technique.

[0005] Therefore, an object of the present invention is to provide a droplet ejection device capable of determining the ejection curve of droplets with higher accuracy than before.

Means for Solving the Problems

[0006] The droplet ejection device of the present invention comprises an ejection head having an ejection surface with a plurality of nozzles opening for ejecting droplets onto a printing medium; a first light source that irradiates a first light toward a flight space in which droplets ejected from the nozzles fly; a second light source provided at a different position from the first light source and irradiating a second light toward the flight space in a direction intersecting with the first light; two moving devices that independently move the first light source and the second light source, respectively, so as to change the direction or position of the irradiation of the first and second light sources; and the first light source relative to the flight space The system comprises a first detection element positioned across from the second light source and detecting the first light, a second detection element positioned across the flight space from the second light source and detecting the second light, and a control device. The control device calculates the amount of deflection of the droplet from the normal flight direction based on a first light-receiving amount for the first light detected by the first detection element and a second light-receiving amount for the second light detected by the second detection element when the first light source irradiates the droplet with the first light and the second light source irradiates the droplet with the second light.

[0007] According to the present invention, by detecting a first amount of light received in relation to the first light, it is possible to detect the presence or absence of a ejected droplet and whether or not the droplet is curved. Furthermore, by detecting a second amount of light received in relation to the second light irradiated in a direction intersecting the first light, it is possible to obtain coordinate information about the direction and amount of curvature of the droplet as it flies. Thus, while it is not possible to obtain coordinate information of a curved droplet using only the first amount of light received in relation to the first light, by using the second amount of light received, it becomes possible to calculate the amount of curvature of the ejected droplet relative to its normal flight direction. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a droplet dispensing device that can determine the curvature of droplet dispensing with higher accuracy than conventional devices. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view showing an image forming apparatus equipped with a droplet ejection device according to one embodiment of the present invention. [Figure 2] This is a plan view showing a droplet dispensing device according to one embodiment of the present invention. [Figure 3] Figure 1 is a cross-sectional view showing the configuration of the discharge head. [Figure 4] This is a block diagram showing the components of the image forming apparatus shown in Figure 1. [Figure 5] This diagram shows how a laser beam is shone onto ink droplets being ejected from the ejection head while they are in flight. [Figure 6] This is a plan view showing a configuration in which laser light from a first light source and laser light from a second light source are irradiated onto an ink droplet. [Figure 7] This is a perspective view showing the configuration of a moving device that rotates and moves the first light source. [Figure 8] This is a diagram to explain the amount of bend in the discharge. [Figure 9] This diagram illustrates the correction for the size of ink droplets ejected by an ejection head moving in the direction of movement. [Figure 10] This diagram illustrates the correction for the ejection cycle of ink droplets ejected by an ejection head moving in the direction of movement. [Figure 11] This diagram illustrates the correction for the ejection cycle of ink droplets ejected by the line head. [Figure 12] This flowchart shows the flow from dispensing failure detection to correction processing. [Figure 13] This figure shows another example of a configuration in which the first and second light sources are moved. [Figure 14] This figure shows another example of a configuration that rotates the first frame. [Modes for carrying out the invention]

[0010] Hereinafter, a droplet dispensing device according to an embodiment of the present invention will be described with reference to the drawings. The droplet dispensing device described below is merely one embodiment of the present invention. Therefore, the present invention is not limited to the following embodiments, and additions, deletions, and modifications are possible without departing from the spirit of the present invention.

[0011] Figure 1 is a perspective view showing an image forming apparatus 1 equipped with a droplet ejection device 1a according to one embodiment of the present invention. In the following description, an example is disclosed in which an inkjet printer capable of printing on a three-dimensional object, the printing medium W, is used as the image forming position 1, but the image forming apparatus 1 also includes inkjet printers capable of printing only on paper. In Figure 1, the mutually orthogonal directions are referred to as the first direction Ds, the second direction Df, and the third direction Dz. In this embodiment, for example, the first direction Ds is the direction of movement of the carriage 3, which will be described later, the second direction Df is the direction of transport of the printing medium W, which will be described later, and the third direction Dz is the vertical direction. In the following description, Ds will be referred to as the direction of movement, Df as the transport direction, and Dz as the vertical direction.

[0012] As shown in Figure 1, the image forming apparatus 1 of this embodiment comprises a housing 2, an operation key 4, a display unit 5, a platen 6 on which the printing medium W is placed, and an upper cover 7. The platen 6 corresponds to a transport device. The image forming apparatus 1 also comprises a droplet ejection apparatus 1a as shown in Figure 2, which has an ejection head 10 and a controller unit 19 including a control device 20 (Figure 4). The ejection head 10 is an inkjet head that ejects, for example, ultraviolet-curable ink droplets Id (Figure 5) as droplets.

[0013] The housing 2 is formed in a box shape. The housing 2 has an opening 2a. Operation keys 4 are provided on the housing 2. A display unit 5 is also provided near the operation keys 4. The operation keys 4 accept user input. The display unit 5 is configured as, for example, a touch panel and displays predetermined information. Part of the display unit 5 also functions as an operation key. The controller unit 19 realizes the printing function and controls the display of the display unit 5 based on input from the operation keys 4 or external input via a communication interface (not shown in the figure).

[0014] The platen 6 is configured to be able to place the printing medium W thereon. The platen 6 has a predetermined thickness and is constituted by, for example, a rectangular plate material having the conveyance direction Df as the longitudinal direction. The platen 6 is removably supported by a platen support base (not shown). The platen support base is configured to be movable in the conveyance direction Df between a printing position where printing on the printing medium W is performed by driving of a conveyance motor 33 (FIG. 4) and a detachable position where the printing medium W is removed from the platen 6. Thereby, the platen 6 relatively moves the discharge surface of the printing medium W in the conveyance direction Df with respect to the discharge head 10. Since the platen 6 moves in the conveyance direction Df during printing, the printing medium W placed on the platen 6 is conveyed along the conveyance direction Df.

[0015] The upper cover 7 is configured to rotate upward when its end is lifted. Thereby, the inside of the housing 2 is exposed.

[0016] As shown in FIG. 2, the droplet discharge device 1a includes a storage tank 62, a carriage 3 on which, for example, two discharge heads 10 (10A, 10B) and two ultraviolet irradiation devices 40 (40A, 40B) are mounted, and a pair of guide rails 1 67. Although two discharge heads 10 and two ultraviolet irradiation devices 40 are provided, the present invention is not limited thereto, and one discharge head 10 and one ultraviolet irradiation device 40 may be provided.

[0017] The carriage 3 is supported by a pair of guide rails 1 1 67 extending in the moving direction Ds, and reciprocates in the moving direction Ds along the guide rails 67. Thereby, the two discharge heads 10 (10A, 10B) and the two ultraviolet irradiation devices 40 (40A, 40B) can reciprocate in the moving direction Ds. Further, the discharge head 10 is connected to the storage tank 62 via a tube 62a.

[0018] In this embodiment, for example, the ejection head 10A ejects ink droplets Id of yellow (Y), magenta (M), cyan (C), and black (K), which are sometimes collectively referred to as color inks. A color image is printed on the printing medium W by ejecting these four ink droplets Id onto the printing medium W. On the other hand, the ejection head 10B ejects white (W) ink droplets Id and clear (Cr) ink droplets Id. When printing a color image on a fabric, for example, as the printing medium W, in order to reduce the influence on the color and material of the fabric, white ink droplets Id are ejected first as a base ink, and then color ink droplets Id are ejected on top of the white ink droplets Id. In addition, clear ink droplets Id are ejected when gloss is to be added or when the printed area is to be protected.

[0019] The storage tanks 62 store ink. Each storage tank 62 is provided for a different type of ink. For example, there are six storage tanks 62, each storing black, yellow, cyan, magenta, white, and clear ink.

[0020] The droplet dispensing device 1a further includes a purge section 50 and a receiving section 54. The receiving section 54 is made of a pair of guide rails that overlap the movement area of ​​the carriage 3. 1 It is positioned on one side of the movement direction Ds of 67. The purge section 50 corresponds to a maintenance unit and consists of a pair of guide rails that overlap the movement area of ​​the carriage 3. 1 It is positioned on the other side of the movement direction Ds among the 67.

[0021] The purging unit 50 includes a cap 51, a suction pump 52, and a lifting mechanism (not shown) that raises and lowers the cap 51 between a suction position and a standby position. The suction pump 52 is connected to the cap 51. In the standby position, the discharge surface NM (Figure 3) is separated from the cap 51. On the other hand, in the suction position, the discharge surface NM is covered by the cap 51, forming a sealed space. When the suction pump 52 is driven while the cap 51 is in the suction position, the sealed space is sucked open, and a purging process is performed in which ink is discharged from the nozzle hole 121a (Figure 3).

[0022] Furthermore, the receiving section 54 receives ink droplets Id ejected from the ejection head 10 through a flushing process.

[0023] Next, the detailed structure of the discharge head 10 will be described. As shown in Figure 3, the discharge head 10 has a plurality of nozzles 121 that discharge ink droplets Id using ink from the storage tank 62. The discharge head 10 has a laminate of a flow channel forming body and a volume changing body. An ink flow channel is formed inside the flow channel forming body, and a plurality of nozzle holes 121a are opened on its lower surface, the discharge surface NM. The volume changing body is driven to change the volume of the ink flow channel. At this time, the meniscus vibrates in the nozzle holes 121a and ink is discharged.

[0024] The flow path forming body of the discharge head 10 is a laminate of multiple plates, and the volume changing section includes a diaphragm 155 and an actuator (piezoelectric element) 160. A common electrode 161, described later, is connected to the diaphragm 155.

[0025] Multiple plates are stacked, from bottom to top, including a nozzle plate 146, a spacer plate 147, a first channel plate 148, a second channel plate 149, a third channel plate 150, a fourth channel plate 151, a fifth channel plate 152, a sixth channel plate 153, and a seventh channel plate 154.

[0026] Each plate has holes and grooves of various sizes formed in it. Inside the flow channel forming body formed by stacking the plates, the holes and grooves are combined to form multiple nozzles 121, multiple individual flow channels 164, and a manifold 122 as ink flow channels.

[0027] The nozzle 121 is formed by penetrating the nozzle plate 146 in the stacking direction. On the discharge surface NM of the nozzle plate 146, multiple nozzle holes 121a, which are the tips of the nozzles 121, are arranged in the transport direction Df to form a nozzle row.

[0028] The manifold 122 supplies ink to the pressure chamber 128 to which discharge pressure is applied. The manifold 122 extends in the transport direction Df and is connected to one end of each of the multiple individual flow channels 164. In other words, the manifold 122 functions as a common flow channel for the ink. The manifold 122 is formed by through holes that penetrate the first flow channel plates 148 to the fourth flow channel plates 151 in the stacking direction, and recesses that are recessed from the lower surface of the fifth flow channel plate 152, overlapping in the stacking direction.

[0029] The nozzle plate 146 is positioned below the spacer plate 147. The spacer plate 147 is made of, for example, stainless steel. The spacer plate 147 has a recess 145 formed by, for example, half-etching, which causes a recess in the thickness direction of the spacer plate 147 from the surface facing the nozzle plate 146, thereby forming a thin-walled portion that forms a damper portion 147a and a damper space 147b. As a result, a damper space 147b is formed between the manifold 122 and the nozzle plate 146, acting as a buffer space.

[0030] A supply port 122a is connected to the manifold 122. The supply port 122a is formed, for example, in a cylindrical shape and is provided at one end in the conveying direction Df. The manifold 122 and the supply port 122a are connected by a flow path not shown in the figure.

[0031] Each individual flow path 164 is connected to the manifold 122. The upstream end of each individual flow path 164 is connected to the manifold 122, and the downstream end is connected to the base end of the nozzle 121. Each individual flow path 164 consists of a first communication hole 125, an individual throttling passage which is a supply throttling passage 126, a second communication hole 127, a pressure chamber 128, and a descender 129, and these components are arranged in this order.

[0032] The first communication hole 125 has its lower end connected to the upper end of the manifold 122, extends upward from the manifold 122 in the stacking direction, and penetrates the upper portion of the fifth flow path plate 152 in the stacking direction.

[0033] The upstream end of the supply throttling passage 126 is connected to the upper end of the first communication hole 125. The supply throttling passage 126 is formed, for example, by half-etching and consists of a groove recessed from the lower surface of the sixth flow channel plate 153. The second communication hole 127 has its upstream end connected to the downstream end of the supply throttling passage 126, extends upward from the supply throttling passage 126 in the stacking direction, and is formed by penetrating the sixth flow channel plate 153 in the stacking direction.

[0034] The pressure chamber 128 has its upstream end connected to the downstream end of the second communication hole 127. The pressure chamber 128 is formed by penetrating the seventh flow channel plate 154 in the stacking direction.

[0035] The descender 129 is formed by penetrating the spacer plate 147, the first flow path plate 148, the second flow path plate 149, the third flow path plate 150, the fourth flow path plate 151, the fifth flow path plate 152, and the sixth flow path plate 153 in the stacking direction. The upstream end of the descender 129 is connected to the downstream end of the pressure chamber 128, and the downstream end is connected to the base end of the nozzle 121. The nozzle 121 overlaps the descender 129 in the stacking direction, for example, and is positioned in the center of the descender 129 in the width direction.

[0036] The diaphragm 155 is laminated on the seventh flow path plate 154 and covers the upper end opening of the pressure chamber 128.

[0037] The actuator 160 includes a common electrode 161, a piezoelectric layer 162, and individual electrodes 163, arranged in this order. The common electrode 161 covers the entire surface of the diaphragm 155. The piezoelectric layer 162 covers the entire surface of the common electrode 161. Individual electrodes 163 are provided for each pressure chamber 128 and are arranged on the piezoelectric layer 162. One actuator 160 is composed of one individual electrode 163, the common electrode 161, and the portion of the piezoelectric layer 162 sandwiched between the two electrodes.

[0038] The individual electrodes 163 are electrically connected to a driver IC. This driver IC receives a control signal from the control device 20, generates a drive signal (voltage signal), and applies it to the individual electrodes 163. In contrast, the common electrode 161 is always kept at ground potential. In this configuration, the active portion of the piezoelectric layer 162 expands and contracts in the planar direction together with the common electrode 161 and the individual electrodes 163 in response to the drive signal. Accordingly, the diaphragm 155 deforms in cooperation, changing the volume of the pressure chamber 128 in a direction that increases or decreases it. As a result, the discharge pressure that causes the ink droplet Id to be ejected from the nozzle 121 is applied to the pressure chamber 128.

[0039] In the ejection head 10, ink flows into the manifold 122 via the supply port 122a, then flows from the manifold 122 into the supply throttling passage 126 via the first communication hole 125, and from the supply throttling passage 126 into the pressure chamber 128 via the second communication hole 127. The ink then flows through the descender 129 and into the nozzle 121. At this point, when ejection pressure is applied to the pressure chamber 128 by the actuator 160, an ink droplet Id is ejected from the nozzle hole 121a.

[0040] As shown in Figure 4, the image forming apparatus 1 includes, in addition to the components described above, a controller unit 19, a reading device 26, motor driver ICs 30 and 31, a head driver IC 32, a transport motor 33, a carriage motor 34, an irradiation device driver IC 35, a purge driver IC 36, a light source driver IC 37, a detection driver IC 38, and a motor driver IC 39. The droplet ejection device 1a includes, in addition to the above components, a first light source 65, a second light source 66, a first detection element 67, a second detection element 68, a first motor 69, and a second motor 70.

[0041] The controller unit 19 includes a control device 20 composed of a CPU, a storage unit (ROM 21, RAM 22, EEPROM 23, HDD 24), and an ASIC 25. The control device 20 is connected to each of the above-mentioned storage units and controls the driver ICs 30-32, 35-39 and the display unit 5.

[0042] The control device 20 performs various functions by executing a predetermined processing program stored in the ROM 21. The control device 20 may be implemented as a single processor in the controller unit 19, or as multiple processors working together. The processing program is read by the reader 26 from a recording medium KB such as a computer-readable magneto-optical disk or USB flash memory and stored in the ROM 21. The RAM 22 stores image data received from an external source and the calculation results of the control device 20. The EEPROM 23 stores various initial setting information entered by the user. The HDD 24 stores specific information, etc.

[0043] The ASIC25 is connected to motor driver ICs 30, 31, and 39, a head driver IC 32, an illumination device driver IC 35, a purge driver IC 36, a light source driver IC 37, and a detection driver IC 38. When the control device 20 receives a print job from the user, it outputs an image recording command to the ASIC25 based on the processing program. The ASIC25 drives each of the driver ICs 30-32 and 35-39 based on the image recording command. The control device 20 moves the platen 6 in the transport direction Df by driving the transport motor 33 with the motor driver IC 30. The control device 20 moves the carriage 3 in the movement direction Ds by driving the carriage motor 34 with the motor driver IC 31.

[0044] The control device 20 converts image data acquired from an external device into ejection data for ejecting ink droplets Id onto the ejection surface. Based on the converted ejection data, the control device 20 ejects ink droplets Id from the ejection head 10 using the head driver IC 32. The control device 20 also irradiates ultraviolet light from each light-emitting diode chip of the ultraviolet irradiation device 40 using the irradiation device driver IC 35. The control device 20 drives the purge unit 50 using the purge driver IC 36. The control device 20 drives the first light source 65 and the second light source 66 using the light source driver IC 37, and drives the first detection element 67 and the second detection element 68 using the detection driver IC 38. The control device 20 also drives the first motor 69 and the second motor 70 using the motor driver IC 39.

[0045] Figure 5 shows the process of irradiating an ink droplet Id, ejected from the ejection head 10 and in flight, with laser light Lz1. Figure 6 is a plan view showing the configuration in which laser light Lz1 from the first light source 65 and laser light Lz2 from the second light source 66 are irradiated onto the ink droplet Id. Figure 7 is a perspective view showing the configuration of a moving device 80 that rotates the first light source 65.

[0046] Figure 5 illustrates a typical configuration in which the laser beam Lz1 emitted from the first light source 65 is detected by the first detection element 67. The configuration in which the laser beam Lz2 (described later in Figure 6) emitted from the second light source 66 is detected by the second detection element 68 is the same as described above, and therefore, unless otherwise noted, the explanation is omitted. In this embodiment, the laser beam Lz1 corresponds to the first beam, and the laser beam Lz2 corresponds to the second beam.

[0047] As shown in Figure 5, the first light source 65 is positioned on one side of the ejection head 10 with respect to the position of the ejection head 10 in the optical axis direction of the laser beam Lz1 emitted from the first light source 65. The first light source 65 irradiates the laser beam Lz1 toward the flight space Sh in which the ink droplet Id ejected from the nozzle 121 is flying. The first light source 65 is housed in a box-shaped light source housing 65a. The light source housing 65a has a slit 65b on the side facing the direction of emission of the laser beam Lz1 emitted from the first light source 65. A lens 65c is positioned inside the light source housing 65a so as to cover the slit 65b from the inside of the light source housing 65a. In this configuration, the laser beam Lz1 emitted from the first light source 65 passes through the lens 65c and is then ejected from the ejection head 10 to irradiate the flying ink droplet Id in the flight space Sh.

[0048] The second light source 66 is positioned differently from the first light source 65. The second light source 66 emits laser light Lz2 towards the flight space Sh in a direction intersecting with laser light Lz1.

[0049] The first detection element 67 is positioned on the other side of the position of the ejection head 10 in the optical axis direction of the laser beam Lz1. The first detection element 67 is positioned across the flight space Sh from the first light source 65. The first detection element 67 detects the laser beam Lz1. Similarly, the second detection element 68 is positioned on the other side of the position of the ejection head 10 in the optical axis direction of the laser beam Lz1. The second detection element 68 is positioned across the flight space Sh from the second light source 66. The second detection element 68 detects the laser beam Lz2.

[0050] As shown in Figure 6, the first light source 65 and the first detection element 67 are supported by a first frame 71 extending in the direction of the optical axis of the laser beam Lz1. The first frame 71 is configured to rotate around the first light source 65 so that the laser beam Lz1 traverses the flight space Sh and the direction of irradiation of the laser beam Lz1 changes. Similarly, the second light source 66 and the second detection element 68 are supported by a second frame 72 extending in the direction of the optical axis of the laser beam Lz2. The second frame 72 is configured to rotate around the second light source 66 so that the laser beam Lz2 traverses the flight space Sh and the direction of irradiation of the laser beam Lz2 changes. In the same figure, the first light source 65 is located on one side of the direction of movement Ds, and the second light source 66 is located on the other side of the direction of movement Ds.

[0051] The configuration of the moving device 80, which rotates the first frame 71 around the first light source 65, will now be described. As shown in Figure 7, the moving device 80 has the first frame 71, the first motor 69, a worm 76, a worm wheel 73, and a connecting shaft 77 provided on the rotation axis 75 of the first motor 69. The worm wheel 73 corresponds to the first gear. The combination of the worm 76 and the worm wheel 73 is generally called a worm gear. By employing a worm gear, the rotational speed of the first motor 69 can be reduced and rotational force can be transmitted, and the torque can be increased.

[0052] The worm 76 and the worm wheel 73 are meshed with each other with their axes perpendicular to each other. The connecting shaft 77 extends along the vertical direction Dz. The worm wheel 73 is mounted at the lower end of the connecting shaft 77, and the base end of the first frame 71 is connected to the upper end of the connecting shaft 77.

[0053] In the above configuration, when the rotation axis 75 of the first motor 69 is rotated around the rotation axis 75 by control by the control device 20, the worm 76 also rotates around the rotation axis 75. At this time, the worm wheel 73 rotates around its axis, and consequently the connecting shaft 77 rotates around its axis via the worm wheel 73. As a result, the first frame 71 rotates with the first light source 65 as the pivot point. This makes it possible to change the irradiation direction of the laser beam Lz1 emitted by the first light source 65.

[0054] Similarly, the moving device 81 includes a second frame 72, a second motor 70, a worm 76, a worm wheel 74, and a connecting shaft 77, all mounted on the rotation axis 75 of the second motor 70. The worm wheel 74 corresponds to the second gear. Note that the rotation of the second frame 72 by the moving device 81 with respect to the second light source 66 is the same as that of the first frame 71, so a detailed explanation is omitted.

[0055] Here, the control device 20 calculates the amount of deviation of the ink droplet Id relative to its normal flight direction. This will be explained in detail below.

[0056] First, the amount of ejection curvature will be explained using Figure 8. As shown in Figure 8, an ink droplet Id ejected from a normal nozzle 121 of the ejection head 10 flies along the normal flight direction Dn. In contrast, an ink droplet Id ejected from a nozzle 121 experiencing ejection failure flies along a curved flight direction Dm that is tilted by an angle α away from the first light source 65 relative to the normal flight direction Dn. In this case, a laser beam Lz1 can be irradiated onto the ink droplet Id flying along the normal flight direction Dn, along a direction perpendicular to the normal flight direction Dn. Furthermore, the laser beam Lz1 can also be irradiated onto the above-mentioned ink droplet Id flying along the curved flight direction Dm that is tilted by an angle α away from the first light source 65 relative to the normal flight direction Dn. However, even though it is possible to irradiate an ink droplet Id flying in a curved flight direction Dm with laser beam Lz1, the ink droplet Id is located in front of the laser beam Lz1 (i.e., in the direction of the laser beam Lz1's propagation). Therefore, the amount of curvature of the ejection, which is the curvature angle α, cannot be detected by laser beam Lz1 alone. To address this, laser beam Lz2 is emitted from a direction intersecting with laser beam Lz1 and irradiated onto the ink droplet Id.

[0057] The second light source 66 irradiates laser light Lz2 toward the flight space Sh. In Figure 6, the coordinates of the ink droplet Id in the plane consisting of the x-axis, which is in the same direction as the movement direction Ds of the ejection head 10, and the y-axis, which is perpendicular to the x-axis and in the same direction as the transport direction Df of the printing medium W, are (x,y). The x-axis corresponds to the first axis, and the y-axis corresponds to the second axis. The intersection of the x-axis and the y-axis is taken as the origin, the acute angle formed by the incident direction Dk1 of the laser light Lz1 and the x-axis in the above plane is θ, and the acute angle formed by the incident direction Dk2 of the laser light Lz2 and the x-axis in the above plane is Φ. Furthermore, the coordinates of the first light source 65 in the plane are (-A,0), and the coordinates of the second light source 66 in the plane are (A,0).

[0058] The control device irradiates the ink droplet Id with laser light Lz1 using the first light source 65 and with laser light Lz2 using the second light source 66. At this time, the control device 20 calculates the bending angle α of the ink droplet Id relative to the normal flight direction Dn as the ejection bending amount, based on the first light received amount for laser light Lz1 detected by the first detection element 67 and the second light received amount for laser light Lz2 detected by the second detection element 68. Specifically, in Figure 6, the control device 20 calculates the x-coordinate in the plane of the ink droplet Id irradiated with laser light Lz1 and laser light Lz2 using x = A × {(tanΦ - tanθ) / (tanΦ + tanθ)}. The control device 20 also calculates the y-coordinate in the plane of the ink droplet Id irradiated with laser light Lz1 and laser light Lz2 using y = (2A × tanθ × tanΦ) / (tanθ + tanΦ). The control device 20 then compares the x and y coordinates calculated for the ink droplet Id flying in the curved flight direction Dm with the x and y coordinates of the ink droplet Id flying in the normal flight direction Dn, which are stored in advance in the ROM 21, etc., and obtains the differences. Based on the differences in the comparison results, the control device 20 calculates the bending angle α as the amount of ejection bending.

[0059] The control device 20 drives the first rotary motor 69 of the moving device 80 when irradiating ink droplets Id ejected from different nozzles 121 with laser light Lz1. This causes the first frame 71 to rotate, changing the direction of the laser light Lz1 and allowing the laser light Lz1 to be irradiated onto ink droplets Id ejected from different nozzles 121. Similarly, the control device 20 drives the second rotary motor 70 of the moving device 81 when irradiating ink droplets Id ejected from different nozzles 121 with laser light Lz2. This causes the second frame 72 to rotate, changing the direction of the laser light Lz2 and allowing the laser light Lz2 to be irradiated onto ink droplets Id ejected from different nozzles 121. This makes it possible to calculate the ejection curvature for each ink droplet Id ejected from each nozzle 121.

[0060] The first frame 71 is positioned so as to intersect the transport direction Df in a plan view when laser light Lz1 is irradiated from the first light source 65. On the other hand, as shown by the dashed line in Figure 6, the first frame 71 is positioned parallel to the transport direction Df in a plan view when laser light Lz1 is not irradiated from the first light source 65. Similarly, the second frame 72 is positioned so as to intersect the transport direction Df in a plan view when laser light Lz2 is irradiated from the second light source 66. On the other hand, as shown by the dashed line in Figure 6, the second frame 72 is positioned parallel to the transport direction Df in a plan view when laser light Lz2 is not irradiated from the second light source 66.

[0061] Furthermore, as shown in Figure 6, the first light source 65, the second light source 66, the first detection element 67, and the second detection element 68 are arranged around the receiving portion 54 so as to surround the receiving portion 54. Note that the arrangement of the first light source 65, the second light source 66, the first detection element 67, and the second detection element 68 is not limited to the above, and they may also be set around the purge portion 50, which is a maintenance unit, so as to surround the purge portion 50.

[0062] As described above, the control device 20 calculates the bending angle α as the amount of bending of the discharge, and then performs a correction related to the discharge according to the amount of bending of the discharge. This will be explained in detail below.

[0063] Figure 9 is a diagram illustrating the correction for the size of ink droplets Id ejected by the ejection head 10 moving in the direction Ds. Figure 10 is a diagram illustrating the correction for the ejection cycle of ink droplets Id ejected by the ejection head 10 moving in the direction Ds.

[0064] As shown in Figure 9, if the amount of ejection deviation exceeds a threshold due to a faulty nozzle 121, the ink droplet Idm will land significantly off-center from its intended position. As a result, the spacing between adjacent ink droplets Id and Idm becomes uneven, leading to an imbalance in ink droplet density.

[0065] Therefore, if the calculated amount of ejection curvature is greater than or equal to a threshold, the control device 20 controls the operation of the ejection head 10 so as to change the size of the ink droplet Id ejected from the nozzle 121 adjacent to the nozzle 121 where the ejection curvature is occurring, according to the amount of ejection curvature. To explain with an example, for ink droplet Id that is relatively close to ink droplet Idm before correction in Figure 9, relatively small ink droplet Ids will land in the corrected version of the same figure. On the other hand, for ink droplet Id that is relatively close to ink droplet Idm before correction in Figure 9, relatively large ink droplet Idb will land in the corrected version of the same figure. This makes it possible to suppress unevenness in ink droplet density.

[0066] Alternatively, if the calculated amount of ejection curvature is greater than or equal to a threshold, the control device 20 controls the operation of the ejection head 10 to change the ejection cycle of the nozzle 121 where the ejection curvature is occurring according to the amount of ejection curvature. To illustrate with an example, in Figure 10, before correction, when an ink droplet Idm lands, the distance between the ink droplet Idm and an adjacent ink droplet Id on one side of the movement direction Ds becomes smaller than the distance between the ink droplet Idm and an adjacent ink droplet Id on the other side of the movement direction Ds. Therefore, the control device 20 changes the ejection cycle of the nozzle 121 where the ejection failure is occurring. As a result, after correction, the distance between the ink droplet Idm and an adjacent ink droplet Id on one side of the movement direction Ds can be made larger than before correction. In other words, by changing the ejection timing, the deviation of the landing position in the movement direction Ds can be corrected. By changing the ejection cycle in this way, it is also possible to suppress the occurrence of unevenness in ink droplet density.

[0067] Figure 11 is a diagram illustrating the correction for the ejection cycle of ink droplets Id ejected by the line head. The correction method when a line head is used as the ejection head 10 is basically the same as that shown in Figure 10.

[0068] The control device 20 controls the operation of the ejection head 10 so as to change the ejection cycle of the nozzle 121 where the ejection curve is occurring according to the amount of ejection curve if the calculated ejection curve is greater than or equal to a threshold. In Figure 11, before correction, when an ink droplet Idm lands, the distance between the ink droplet Idm and an adjacent ink droplet Id on one side of the transport direction Df becomes smaller than the distance between the ink droplet Idm and an adjacent ink droplet Id on the other side of the transport direction Df.

[0069] Therefore, the control device 20 changes the ejection cycle of the nozzle 121 where ejection failure is occurring. This makes it possible to make the distance between an ink droplet Idm and an adjacent ink droplet Id on one side of the transport direction Df the same as the distance between an ink droplet Idm and an adjacent ink droplet Id on the other side of the transport direction Df after correction. In other words, by changing the ejection timing, the deviation of the landing position in the transport direction Df can be corrected. This makes it possible to suppress the occurrence of unevenness in ink droplet concentration. Note that the correction regarding the size of the ink droplet Id ejected by the line head is the same as in Figure 9, so the explanation is omitted.

[0070] Figure 12 is a flowchart showing the flow from the ejection failure detection process to the correction process. As shown in Figure 12, the control device 20 calculates the ejection curvature amount in the ejection failure detection process (step S1). If the calculated ejection curvature amount is greater than or equal to a threshold (YES in step S2), the control device 20 causes the purge unit 50 to perform the purging process of the ejection head 10 (step S3). On the other hand, if the calculated ejection curvature amount is less than the threshold (NO in step S2), the control device 20 causes the ejection head 10 to perform normal printing (step S4). Note that the ejection failure detection process may also determine whether or not there is any non-ejection.

[0071] After the processing in step S3, the control device 20 performs the ejection failure detection process again (step S5). That is, the control device 20 recalculates the ejection curvature for the nozzle 121 for which the ejection curvature was calculated in step S1. If the calculated ejection curvature is greater than or equal to a threshold (YES in step S6), the control device 20 determines whether the degree of ejection failure is within a correctable range (step S7). In this case, cases where correction is not possible include, for example, when the ejection curvature has reached a preset upper limit, when the number of nozzles 121 experiencing ejection failure has reached a preset upper limit, and when two or more nozzles 121 experiencing ejection failure are adjacent to each other. On the other hand, if the calculated ejection curvature is less than a threshold (NO in step S6), the control device 20 causes the ejection head 10 to perform normal printing (step S9).

[0072] If the degree of the discharge defect is within a correctable range (YES in step S7), the control device 20 performs the correction process described above (step S8) and returns to the process in step S1. On the other hand, if the degree of the discharge defect is not within a correctable range (NO in step S7), the control device 20 warns that the discharge head 10 should be replaced (step S10). Specifically, the control device 20 outputs a warning sound from the audio device or displays a warning on the display unit 5.

[0073] As explained above, the droplet ejection device 1a can detect the presence or absence of ejected ink droplets Id and whether or not the ink droplets Id are curved by detecting a first amount of light received with respect to the laser beam Lz1. Furthermore, by detecting a second amount of light received with respect to the laser beam Lz2, which is irradiated in a direction intersecting the laser beam Lz1, coordinate information can be obtained regarding the direction and amount of curvature of the ink droplets Id as they fly. Thus, while the coordinate information of a curved ink droplet Id cannot be obtained using only the first amount of light received with respect to the laser beam Lz1, by using the second amount of light received with respect to the laser beam Lz2, it becomes possible to calculate the amount of curvature of the ejected ink droplets Id relative to their normal flight direction Dn.

[0074] Furthermore, in this embodiment, the first light source 65 and the second light source 66 rotate and move so that the direction of irradiation of laser beams Lz1 and Lz2 toward the flight space Sh changes. This makes it easier to irradiate the ink droplet Id, which is flying in a curved direction, with either laser beam Lz2 or laser beam Lz1. As a result, the curvature of the ejected ink droplet Id can be detected with high precision.

[0075] Furthermore, in this embodiment, the first frame 71 can be rotated by the first motor 69, and the second frame 72 can be rotated by the second motor 70. This makes it possible to rotate the first frame 71 and the second frame 72 with a low-cost, simple, and compact configuration.

[0076] Furthermore, in this embodiment, the first frame 71 is positioned parallel to the transport direction Df in a plan view when the laser beam Lz1 is not irradiated from the first light source 65. Similarly, the second frame 72 is positioned parallel to the transport direction Df in a plan view when the laser beam Lz2 is not irradiated from the second light source 66. This makes it possible to save space in the droplet dispensing device 1a.

[0077] Furthermore, in this embodiment, the first light source 65, the second light source 66, the first detection element 67, and the second detection element 68 are arranged around the receiving section 54 or the purging section 50. In this case, since the first light source 65 and the second light source 66, which are heat sources, are not moved, the ambient temperature around the ejection head 10 tends to stabilize. This suppresses the influence of temperature on the ejection head 10, and therefore prevents changes in the drive waveform. In addition, interference with the ejection head 10 during the printing process on the printing medium W can be prevented.

[0078] Furthermore, in this embodiment, the first light source 65 is located on one side of the movement direction Ds, and the second light source 66 is located on the other side of the movement direction Ds. In this case, the thermal influence on the discharge head 10 can be suppressed more effectively than when the heat sources, the first light source 65 and the second light source 66, are located together on one side of the movement direction Ds.

[0079] Furthermore, in this embodiment, the x-coordinate in the plane of the ink droplet Id irradiated by laser beams Lz1 and Lz2 is calculated by x = A × {(tanΦ - tanθ) / (tanΦ + tanθ)}. The y-coordinate in the plane of the ink droplet Id irradiated by laser beams Lz1 and Lz2 is calculated by y = (2A × tanθ × tanΦ) / (tanθ + tanΦ). This allows for more accurate acquisition of the amount of curvature of the ink droplet Id.

[0080] Furthermore, in this embodiment, if the calculated amount of ejection curvature is greater than or equal to a threshold, the control device 20 controls the operation of the ejection head 10 to change the size of the ink droplet Id ejected from the nozzle 121 adjacent to the nozzle 121 where the ejection curvature is occurring, according to the amount of ejection curvature. Alternatively, if the calculated amount of ejection curvature is greater than or equal to a threshold, the control device 20 controls the operation of the ejection head 10 to change the ejection timing of the nozzle 121 where the ejection curvature is occurring, according to the amount of ejection curvature. In this respect, the landing position of the ink droplet Idm ejected from the defective nozzle causing the ejection curvature will be shifted from the desired position. However, by changing the size of the ink droplet Id ejected from each nozzle 121 adjacent to the defective nozzle or by changing the ejection cycle of the defective nozzle, it is possible to suppress the occurrence of unevenness in ink droplet concentration.

[0081] (modified version) The present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. For example, the following:

[0082] In the above embodiment, the first light source 65 and the second light source 66 were rotated to change the irradiation direction of the laser beams Lz1 and Lz2, thereby irradiating the ink droplets Id ejected from each nozzle 121 with the laser beams Lz1 and Lz2. However, the configuration for irradiating the ink droplets Id with the laser beams Lz1 and Lz2 is not limited to the above configuration. Figure 13 shows another example of a configuration in which the first light source and the second light source are moved.

[0083] As shown in Figure 13, the first frame 71 and the second frame 72 can be arranged so as to be orthogonal to each other. In this figure, the first frame 71 is arranged to extend in the movement direction Ds, and the second frame 72 is arranged to extend in the transport direction Df. In this case, the first frame 71 is configured to be movable in the transport direction Df, and the second frame 72 is configured to be movable in the movement direction Ds. With this configuration as well, the laser beams Lz1 and Lz2 can be irradiated onto the ink droplets Id ejected from each nozzle 121.

[0084] Furthermore, in the above embodiment, the first frame 71 was rotated by the first motor 69 and the second frame 72 was rotated by the second motor 70. However, the configuration for rotating the first frame 71 and the second frame 72 is not limited to the above configuration. Figure 14 shows another example of a configuration for rotating the first frame 71.

[0085] As shown in Figure 14, the first light source 65 and the first detection element 67 are supported by the first frame 71a. The first frame 71a is arranged so as to intersect, for example, the movement direction Ds and the transport direction Df. The first frame 71a has an extendable and retractable portion 79. Such a first frame 71a is rotated by the first linear actuator 84.

[0086] The first linear actuator 84 includes a linear guide 86 extending in the direction of movement Ds and a slider 86 sliding along the linear guide 86. a It has the following. As described above, when the first frame 71a is rotated by the first motor 69, the slider 86 aAs the slider 86 moves linearly along the linear guide 86 to one side in the direction of movement Ds, the telescopic portion 79 of the first frame 71a retracts. In this way, the first frame 71a can be rotated by the first linear actuator 84. In this regard, when the first frame 71 is rotated in a plane by the power of the first motor 69, the rotation angle of the first motor 69 becomes the control factor. Therefore, the larger the amount of rotational movement of the first frame 71, the larger the amount of displacement of the first frame 71 relative to the designated position to which it moves. In contrast, in the first linear actuator 84, the control factor when rotating the first frame 71a in a plane is the slider 86 on the linear guide 86. a This is the position. Therefore, even if the amount of rotational movement of the first frame 71a in the plane is increased, the positional accuracy of the first frame 71a does not change. This makes it possible to rotate the first frame 71a with high precision. Although the first frame 71a is provided with an extendable section 79, it is not limited to this, and the slider 86 can be used without providing the extendable section 79 to the first frame 71a. a It is also possible to employ a guide mechanism that guides along the linear guide 86. Note that the function of the second linear actuator 85, which rotates the second frame 72a supporting the second light source 66 and the second detection element 68, is the same as that of the first linear actuator 84, so its explanation is omitted.

[0087] Furthermore, in the above embodiment, the power of the first motor 69 is converted into rotational force that rotates the first frame 71 via the connecting shaft 77 by the worm 76 and worm wheel 74, but the embodiment is not limited to this. For example, the power of the first motor 69 can also be directly converted into rotational force that rotates the first frame 71 via the connecting shaft 77. [Explanation of Symbols]

[0088] 1a Droplet discharge device 3 carriages 6 Platen 10 Discharge heads 20 Control device 50 Purge section 54 Receiving part 65 1st light source 66 Second light source 67 First detection elements 68 Second detection element 69 First Motor 70 Second motor 71,71a First frame 72,72a Second frame 73,74 Worm Wheel 80,81 Mobile device 84. First Linear Actuator 85. Second Linear Actuator 121 Nozzles Df Conveying direction Dn Normal flight direction Ds moving direction Lz1, Lz2 laser light NM discharge surface Sh flight space W Printing medium

Claims

1. A discharge head having a discharge surface with multiple nozzles that discharge droplets onto the printing medium, A first light source that irradiates a first light into the flight space in which the droplets ejected from the nozzle are flying, A second light source is provided at a different location from the first light source and emits a second light in a direction intersecting with the first light toward the flight space, Two moving devices that independently move the first light source and the second light source so that the irradiation direction or irradiation position of the first light and the second light source changes, A first detection element is positioned across the flight space from the first light source and detects the first light, A second detection element is positioned across the flight space from the second light source and detects the second light, A control device is provided, The control device is A droplet dispensing device that, when the first light source is moved by one of the moving devices and the second light source is moved by the other of the moving devices, and when the first light source irradiates the droplet with the first light and the second light source irradiates the droplet with the second light, calculates the amount of dispensing curvature of the droplet relative to the normal flight direction based on the first amount of light received for the first light detected by the first detection element and the second amount of light received for the second light detected by the second detection element.

2. The aforementioned mobile device supports the first light source and the first detection element and has a first frame configured to be rotatable around the first light source so that the first light traverses the flight space. The droplet ejection device according to claim 1, wherein the other moving device supports the second light source and the second detection element and has a second frame configured to be rotatable with respect to the second light source so that the second light traverses the flight space.

3. The aforementioned moving device has a first gear connected to the first frame and a first motor that rotates the first gear. The droplet dispensing device according to claim 2, wherein the other moving device has a second gear connected to the second frame and a second motor for rotating the second gear.

4. The aforementioned moving device has a first linear actuator that rotates the first frame, The droplet dispensing device according to claim 2, wherein the other moving device has a second linear actuator for rotating the second frame.

5. The device further comprises a conveying device for conveying the printing medium in the conveying direction, The first frame is positioned so as to intersect the transport direction in a plan view when the first light is irradiated from the first light source, and is positioned parallel to the transport direction in a plan view when the first light is not irradiated. The droplet dispensing device according to claim 2, wherein the second frame is arranged so as to intersect the transport direction in a plan view when the second light is irradiated from the second light source, and is arranged parallel to the transport direction in a plan view when the second light is not irradiated.

6. A carriage for moving the discharge head in the direction of movement, A receiving portion is provided on one side of the aforementioned direction of movement to receive droplets discharged from the discharge head during the flushing process of the discharge head, The system further comprises a maintenance unit provided on the other side of the aforementioned direction of movement, which performs purging on the discharge head, The droplet dispensing device according to claim 1, wherein the first light source, the second light source, the first detection element, and the second detection element are arranged around the receiving portion or around the maintenance unit.

7. The carriage further comprises a carriage for moving the discharge head in the direction of movement. The droplet dispensing device according to claim 1, wherein the first light source is arranged on one side of the direction of movement, and the second light source is arranged on the other side of the direction of movement.

8. Let (x, y) be the coordinates of the droplet in a plane comprising a first axis in the same direction as the movement direction of the ejection head and a second axis perpendicular to the first axis and in the same direction as the transport direction of the printing medium, the origin be the coordinates of the intersection of the first axis and the first axis, θ be the acute angle between the incident direction of the first light and the first axis in the plane, Φ be the acute angle between the incident direction of the second light and the first axis in the plane, the coordinates of the first light source in the plane be (-A, 0), and the coordinates of the second light source in the plane be (A, 0). The control device is The x-coordinate in the plane of the droplet irradiated with the first and second light is calculated by x = A × {(tanΦ - tanθ) / (tanΦ + tanθ)}, The droplet dispensing device according to claim 1, wherein the y-coordinate in the plane of the droplet irradiated with the first light and the second light is calculated by y = (2A × tanθ × tanΦ) / (tanθ + tanΦ).

9. The droplet dispensing device according to claim 1, wherein the control device controls the operation of the dispensing head so as to change the size of the droplets dispensed from a nozzle adjacent to the nozzle where the dispensing curve is occurring in accordance with the dispensing curve, or so as to change the dispensing cycle of the nozzle where the dispensing curve is occurring in accordance with the dispensing curve, when the dispensing curve is greater than or equal to a threshold.

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