Liquid droplet discharge device

Abstract

To provide a liquid droplet discharge device capable of determining presence / absence of discharge bend of liquid droplets with high accuracy.SOLUTION: A liquid droplet discharge device comprises a control device that rotates a detection device about a rotation center by a rotation device such that an optical-axis angle relative to a head becomes a first angle to establish a first posture, receives a first light reception amount related to first light detected by a detection element when irradiating, by a light source, liquid droplets discharged into a flight space from a nozzle with light as the first light while moving the detection device in a forward direction by a moving device, rotates the detection device about the rotation center by the rotation device such that the optical-axis angle becomes a second angle to establish a second posture, and calculates a discharge bend amount relative to a normal flight direction of the liquid droplets based on a second light reception amount related to the second light detected by the detection element when irradiating, by the light source, the liquid droplets discharged into the flight space from the same nozzle as the nozzle light as the second light while moving the detection device in a return direction by the moving device.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a droplet ejection device that is provided in a printing device such as an inkjet printer. [Background technology]

[0002] Conventionally, a printing device is known in which the optical axis of light emitted from a light source is tilted relative to the ejection head, and the light from the light source is irradiated onto droplets ejected from the ejection head that is scanned in the forward and backward directions (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-188853 Summary of the Invention [Problem to be solved by the invention]

[0004] However, while the above-mentioned conventional technology can detect the presence or absence of ejected droplets, it cannot detect the deviation of the droplets from their normal flight direction. In other words, it cannot detect whether the droplets are flying in a curved direction while overlapping with the optical axis of the light, which means that it is not possible to detect the planar coordinates of the ejected droplets.

[0005] Therefore, an object of the present disclosure is to provide a droplet ejection device that can determine with high accuracy whether or not the droplets are ejected in a deflected direction. [Means for solving the problem]

[0006] The droplet ejection device of the present disclosure includes a head having a nozzle surface in which a plurality of nozzles are opened for ejecting droplets onto a print medium, a light source that irradiates light toward a flight space through which droplets ejected from the nozzles fly, and a detection device that is disposed across the flight space from the light source and has a detection element that detects the light, a rotation device that rotates the detection device about a predetermined rotation center as a base point so that the direction of irradiation of the light changes within a plane parallel to the nozzle surface, a movement device that moves the detection device in predetermined forward and backward directions, and a control device, and the control device performs a process of rotating the detection device about the rotation center as a base point to set the detection device to a first attitude so that the angle of the optical axis with respect to the head becomes a first angle, and a process of moving the detection device in the first attitude in the forward direction by the movement device. The method includes the steps of: receiving a first amount of received light of the first light detected by the detection element when the light source irradiates the droplets ejected from the nozzle into the flight space with light as a first light; rotating the detection device using the rotation device to a second position using the rotation center as a base point so that the angle of the optical axis relative to the head is a second angle different from the first angle; receiving a second amount of received light of the second light detected by the detection element when the light source irradiates the droplets ejected from the same nozzle into the flight space with light as the second light while moving the detection device in the second position in the return direction using the movement device; and calculating the amount of deflection of the droplets ejected relative to the normal flight direction based on the first amount of received light and the second amount of received light.

[0007] According to the present disclosure, a light source in a first position irradiates a droplet ejected from a nozzle with a first light, and a light source in a second position irradiates a droplet ejected from the same nozzle with a second light. Then, by detecting the first amount of received light, it is possible to detect the presence or absence of an ejected droplet and the volume of the droplet. Furthermore, by detecting the second amount of received light, it is possible to detect whether the droplet whose presence has been detected is deflected while overlapping with the optical axis of the first light. In other words, it is possible to detect how far the droplet is deflected in flight along the optical axis of the first light (in the depth direction of the optical axis). Thus, while it is not possible to determine whether the droplet is deflected while overlapping with the optical axis of the first light based on the first amount of received light alone, it is possible to accurately calculate the amount of deflection of the droplet relative to the normal flight direction by using the second amount of received light related to the second light. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a droplet ejection device that can determine with high accuracy whether or not the droplets are ejected in a deflected manner. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a plan view showing a droplet ejection device according to an embodiment. [Figure 2] 2 is a block diagram showing an example of components of a printing device in which the droplet ejection device of FIG. 1 is provided. [Figure 3] FIG. 2 is a bottom view illustrating the configuration of a line head. [Figure 4] 10A and 10B are diagrams illustrating how ink droplets ejected from an ejection head and flying are irradiated with laser light. [Figure 5] 3 is a plan view showing a light source in a first position and a detection element corresponding to the light source, and a light source in a second position and a detection element corresponding to the light source. FIG. [Figure 6] 10 is a diagram showing the relationship between the position of the rotation center of a frame and the distance required to rotate the frame. FIG. [Figure 7]7A and 7B are diagrams showing examples of the arrangement of the light source and the detection element relative to the line head. [Figure 8] 8A and 8B are diagrams showing examples of the arrangement of light sources and detection elements between one line head and the other adjacent line head. [Figure 9] 5A and 5B are diagrams illustrating examples of the arrangement of light sources and detection elements relative to a nozzle surface. [Figure 10] 10A and 10B are diagrams illustrating examples of arrangement of light sources and detection elements in the transport direction. [Figure 11] FIG. 2 is a diagram showing the direction of irradiation of laser light from a light source. [Figure 12] 10A and 10B are diagrams illustrating examples of a light blocking portion provided between a nozzle surface and an optical axis. [Figure 13] 10A and 10B are diagrams illustrating examples of a light blocking portion provided between a nozzle surface and an optical axis. [Figure 14] 10A and 10B are diagrams illustrating the positions of optical axes of light sources between adjacent line heads. [Figure 15] FIG. 10 is a diagram showing the timing of laser light irradiation in each unit. DETAILED DESCRIPTION OF THE INVENTION

[0010] A droplet ejection device according to an embodiment of the present disclosure will be described below with reference to the drawings. The droplet ejection device described below is merely one embodiment of the present disclosure. Therefore, the present disclosure is not limited to the following embodiment, and additions, deletions, and modifications are possible within the scope of the present disclosure.

[0011] (First embodiment) FIG. 1 is a plan view showing a droplet ejection device 100 according to one embodiment. The droplet ejection device 100 in this embodiment is a line head type. In FIG. 1, directions that are perpendicular to each other are referred to as a first direction Df and a second direction Ds. In this embodiment, the first direction Df corresponds to the transport direction of the print medium W, and the second direction Ds corresponds to the intersecting direction that is perpendicular to the transport direction. Hereinafter, Df will be referred to as the transport direction, and Ds will be referred to as the intersecting direction.

[0012] As shown in FIG. 1, the droplet ejection device 100 includes a line head group 70, a pair of transport rollers 60, a platen 61, a plurality of storage tanks 62, and a plurality of tubes 63.

[0013] The line head group 70 has, for example, five line heads 71. The number of line heads 71 ​​included in the line head group 70 is not limited to five and can be set as appropriate. The line heads 71 ​​are provided, for example, corresponding to the colors of ink. The line heads 71 ​​are arranged side by side at approximately equal intervals in the transport direction Df. The line heads 71 ​​extend in the intersecting direction Ds. The line head 71 is provided with a plurality of ejection heads 10 (FIG. 3) described below. The line head 71 corresponds to a head. However, a serial head (including a configuration in which a plurality of linear ejection heads are arranged) may be used instead of the line head 71.

[0014] The platen 61 supports from below the print medium W. For example, the platen 61 has a predetermined thickness and is made of a rectangular plate material with the transport direction Df as its longitudinal direction.

[0015] The pair of transport rollers 60 extend in the cross direction Ds. The dimension of the transport roller 60 in the cross direction Ds is larger than the dimension of the print medium W in the cross direction Ds. One of the pair of transport rollers 60 is connected to a transport motor 33 (FIG. 2) described below, and is arranged on one side (e.g., the front) of the platen 61 in the transport direction Df. The other of the pair of transport rollers 60 is arranged on the other side (e.g., the rear) of the platen 61 in the transport direction Df. When the transport motor 33 is driven, the transport roller 60 rotates, thereby transporting the print medium W on the platen 61 in the transport direction Df. In this embodiment, as an example, the print medium W is transported from the front to the rear.

[0016] Ink is stored in the storage tanks 62. A storage tank 62 is provided for each type of ink. For example, five storage tanks 62 are provided, each storing black, yellow, cyan, magenta, and white ink. A color image is printed by ejecting ink droplets of the four colors of black, yellow, cyan, and magenta onto the print medium W. A base is formed by ejecting white ink droplets onto the print medium W.

[0017] The tube 63 is provided corresponding to the storage tank 62. The tube 63 connects the storage tank 62 and the plurality of ejection heads 10 provided in the line head 71.

[0018] FIG. 2 is a block diagram showing an example of components of the printing device 1 in which the droplet ejection device 100 of FIG. 1 is provided.

[0019] As shown in FIG. 2, the printing device 1 includes operation keys 4, a display unit 5, and a reading device 26. In addition to the above-mentioned components, the droplet ejection device 100 includes an ejection head 10, a controller unit 19, a transport motor 33, motor driver ICs 30, 35, and 36, a head driver IC 31, a light source driver IC 32, and a detection driver IC 34. The droplet ejection device 100 also includes a detection device Dd (FIG. 4), which will be described later, a rotation motor 68, a movement motor 69, and a frame 72. The detection device Dd has a light source 65, a detection element 67, and the frame 72. The rotation motor 68, the frame 72, and a coupling mechanism such as a gear (not shown) that connects the rotation motor 68 and the frame 72 correspond to the rotation device, and the movement motor 69, the frame 72, and a ball screw or rack-and-pinion (not shown) that connects the movement motor 69 and the frame 72 correspond to the movement device.

[0020] The operation keys 4 accept operation inputs from the user. The display unit 5 is configured, for example, as 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 based on inputs from the operation keys 4 or external inputs via a communication interface (not shown), and also controls the display of the display unit 5.

[0021] The controller unit 19 has a control device 20 configured by a CPU, storage units (ROM 21, RAM 22, EEPROM 23, HDD 24), and an ASIC 25. The control device 20 is connected to the storage units and controls the driver ICs 30 to 32, 34 to 36, the display unit 5, and the reading device 26.

[0022] The control device 20 performs various functions by executing predetermined processing programs stored in the ROM 21. The control device 20 may be implemented as a single processor in the controller unit 19, or may be implemented as multiple processors cooperating with each other. The processing programs are read by the reading device 26 from a computer-readable recording medium KB such as a magneto-optical disk or a USB flash memory, and stored in the ROM 21. The RAM 22 stores image data received from the outside and calculation results of the control device 20. The EEPROM 23 stores various initial setting information input by the user. The HDD 24 stores various information.

[0023] The ASIC 25 is connected to motor driver ICs 30, 35, and 36, a head driver IC 31, a light source driver IC 32, and a detection driver 34. When the control device 20 accepts a print job from a user, it outputs a print command to the ASIC 25 based on a processing program. The ASIC 25 controls the driver ICs 30 to 32 and 34 to 36 based on the print command. The control device 20 moves the platen 61 in the conveyance direction Df by driving the conveyance motor 33 using the motor driver IC 30.

[0024] The control device 20 converts image data acquired from an external device or the like into ejection data for ejecting ink droplets onto the print medium W. The control device 20 controls the head driver IC 31 to eject ink droplets from the ejection head 10 based on the converted ejection data. The control device 20 also controls the light source 65 using the light source driver IC 32 and the detection element 67 using the detection driver IC 34. The control device 20 also controls the rotation motor 68 using the motor driver IC 35. By controlling the rotation motor 68, a frame 72 supporting the light source 65 and the detection element 67 rotates so as to change the irradiation direction of a laser beam Lz (FIG. 4) described below within a plane parallel to the nozzle surface NM (FIG. 4) described below. Furthermore, the control device 20 controls the movement motor 69 using the motor driver IC 36. By controlling the movement motor 69, the frame 72 supporting the light source 65 and the detection element 67 moves in a predetermined forward direction and a backward direction. The rotation and movement of the frame 72 will be described in detail later.

[0025] Fig. 3 is a bottom view showing the configuration of the line head 71. As shown in Fig. 3, the line head 71 is provided with ten ejection heads 10, for example. As the ejection heads 10, for example, inkjet heads that eject ink droplets as droplets can be used. However, the ejection heads 10 are not limited to those described above.

[0026] Of the ten ejection heads 10, five are arranged upstream in the transport direction Df, and the remaining five are arranged downstream in the transport direction Df. The ejection heads 10 include ejection heads 111, 113, 115, 117, and 119 arranged upstream in the transport direction Df. The ejection heads 10 include ejection heads 112, 114, 116, 118, and 120 arranged downstream in the transport direction Df. The upstream ejection heads 10 are arranged at approximately equal intervals. The downstream ejection heads 10 are arranged at approximately equal intervals and are offset by a predetermined distance in the intersecting direction Ds from the upstream ejection heads 10. That is, the multiple ejection heads 10 in the line head 71 are arranged in a staggered pattern in the intersecting direction Ds. The arrangement of the ejection heads 10 is not limited to a staggered pattern.

[0027] Fig. 4 is a diagram showing how a laser beam Lz is irradiated onto an ink droplet Id in flight after being ejected from the ejection head 10. In this embodiment, the laser beam Lz corresponds to light. As shown in Fig. 4, the ejection head 10 has a nozzle surface NM in which a plurality of nozzles Nz are opened, which eject ink droplets Id onto the print medium W. For simplicity, only one nozzle Nz is shown in Fig. 4.

[0028] The light source 65 is disposed on one side of the ejection head 10 in a direction parallel to the optical axis La of the laser beam Lz emitted from the light source 65. The detection element 67 is disposed across the flight space Sh from the light source 65. The detection element 67 is disposed on the other side of the ejection head 10 in the same direction. The light source 65 irradiates the laser beam Lz toward the flight space Sh into which the ink droplets Id ejected from the nozzles Nz fly. The light source 65 is disposed in a box-shaped light source housing 65a. The light source housing 65a has a slit 65b on the side in the emission direction of the laser beam Lz emitted from the light source 65. A lens 65c is disposed in the light source housing 65a so as to cover the slit 65b from the inside of the light source housing 65a. One or more lenses may be provided in addition to the lens 65c. The light source 65 and the detection element 67 are supported by a frame 72 extending along the optical axis La of the laser beam Lz.

[0029] The laser light Lz emitted from the light source 65 passes through the lens 65c and is then irradiated onto the ink droplets Id that have been ejected from the ejection head 10 and are flying through the flight space Sh. The detection element 67 detects the amount of light received from the laser light Lz after the laser light Lz emitted from the light source 65 has passed through the flight space Sh. The control device 20 executes a discharge defect detection process based on a comparison between the signal output from the detection element 67 and a reference signal to detect discharge defects such as speed abnormalities of the ink droplets Id, volume abnormalities of the ink droplets Id, and deflected discharge (skew) of the ink droplets Id. Note that deflected discharge refers to the ink droplets Id flying in a direction different from their normal flight direction. A method for detecting deflected discharge will be described below.

[0030] FIG. 5 is a plan view showing the light source 65 and the detecting element 67 in the first position P1 and the light source 65 and the detecting element 67 in the second position P2. As shown in FIG. 5, the control device 20 first rotates the frame 72 of the detecting device Dd by the rotation motor 68 about the rotation center CR as the base point so that the angle θ of the optical axis La relative to the line head 71 becomes a first angle, thereby setting the detecting device Dd in the first position P1. For example, in a configuration in which the light source 65 is disposed at one end of the line head 71 in the longitudinal direction and the detecting element 67 is disposed at the other end of the line head 71 in the longitudinal direction in a planar view, the angle θ can be the angle formed between the optical axis La and the long side of the line head 71 in a planar view. In this case, when the angle θ is 0°, the optical axis La and the long side of the line head 71 are parallel. In other words, when the angle θ is 0°, the laser light Lz from the light source 65 is emitted in a direction parallel to the long side of the line head 71. The first angle θ is, for example, 10° to 30°.

[0031] After the frame 72 is set to the first posture P1, the control device 20 causes the movement motor 69 to move the frame 72 of the detection device Dd in the forward direction Dt, while causing the light source 65 to irradiate the ink droplets Id ejected from each nozzle Nz into the flight space Sh with a laser beam Lz as the first light. The irradiation of the ink droplets Id with the laser beam Lz is performed for all nozzles Nz. At this time, the control device 20 receives a first received light amount of the laser beam Lz corresponding to the first light detected by the detection element 67. Note that the forward direction Dt is, for example, a direction parallel to the short-side direction of the line head 71 in a plan view, and a backward direction Dr, described below, is the opposite direction to the forward direction Dt.

[0032] Next, the control device 20 rotates the frame 72 of the detection device Dd with the rotation motor 68 about the rotation center CR as the base point so that the angle θ of the optical axis La relative to the line head 71 becomes a second angle different from the first angle, thereby setting the detection device Dd in a second position P2. The second angle θ is, for example, −10° to −30°. In FIG. 5, the frame 72 in the second position P2, and the light source 65 and detection element 67 supported by the frame 72 are shown by dashed lines.

[0033] After the frame 72 is set to the second posture P2, the control device 20 causes the movement motor 69 to move the frame 72 of the detection device Dd in the backward direction Dr while causing the light source 65 to irradiate the ink droplets Id ejected from each nozzle Nz into the flight space Sh with a laser beam Lz as the second light. The irradiation of the ink droplets Id with the laser beam Lz is performed for all nozzles Nz. At this time, the control device 20 receives a second received light amount of the laser beam Lz corresponding to the second light detected by the detection element 67.

[0034] The control device 20 calculates the amount of deflection of the ink droplet Id relative to the normal flight direction based on the first amount of received light and the second amount of received light obtained by the above method.

[0035] Here, the position where the rotation center CR should be set will be explained. In this embodiment, the rotation center CR is set within the optical path LP between the light source 65 and the detection element 67. More specifically, the rotation center CR is located in the central region of the optical path LP between the light source 65 and the detection element 67, as shown in FIG. 5. The central region is an area that includes the center of the optical path LP, and in this embodiment, it is defined as follows.

[0036] In FIG. 5 , the angle of the optical axis La relative to the line head 71 is θ. When the angle θ between the optical axis La and the long side of the line head 71 in a plan view is 0°, the direction parallel to the optical axis La is the longitudinal direction DL, and the direction perpendicular to the longitudinal direction DL is the direction DW. Furthermore, the dimension of the line head 71 in the longitudinal direction DL is Ly, and the distance in the longitudinal direction DL between the light source 65 and the rotation center CR is y0. Furthermore, when the rotation center CR is set to the center of the optical path LP between the light source 65 and the detecting element 67, and the frame 72 is rotated clockwise and counterclockwise around the rotation center CR by the movement motor 69, the movement distance Lw of the detecting element 67 in the direction DW is Lw0. When the rotation center CR is set in the central region of the optical path LP and the frame 72 is rotated around the rotation center CR, the movement distance Lw of the detecting element 67 in the direction DW can be calculated using the following formula 1: The movement distance Lw is the distance between a predetermined position (for example, the center in the longitudinal direction) of the detection element 67 in the first posture P1 and a predetermined position of the detection element 67 in the second posture P2.

[0037] (Number 1) Lw=(|y0-(Ly / 2)|+(Ly / 2))×tanθ×2

[0038] In this embodiment, in order to minimize the movement distance Lw and save space, as shown in FIG. 6, the rotation center CR is set so that the movement distance Lw is 1.5×Lw0 or less. That is, the position in the central region of the optical path LP where the rotation center CR should be set is a position in the longitudinal direction DL, including the position Pc of the rotation center CR when the rotation center CR is set at the center of the optical path LP. More specifically, the position in the central region of the optical path LP is a position that can be taken within a range from position Pe1, which is closer to the light source 65 than the position Pc, to position Pe2, which is closer to the detection element 67 than the position Pc. Note that the movement distance Lw (i.e., movement distance Lw0) when the rotation center CR is located at the center of the optical path LP (i.e., position Pc), is the same value as the movement distance in the direction DW of the light source 65.

[0039] In this way, by setting the rotation center CR within the range from position Pe1 to position Pe2 in the longitudinal direction DL (in other words, within the range where the movement distance Lw is 1.5 x Lw0 or less), the movement distance Lw can be made as small as possible, thereby saving space.

[0040] Next, a description will be given of the arrangement of the light source 65 and the detection element 67 relative to the line head 71. Figures 7A and 7B are diagrams showing examples of the arrangement of the light source 65 and the detection element 67 relative to the line head 71.

[0041] The line head 71 is formed in a rectangular shape in a plan view. The line head 71 extends in the longitudinal direction DL of the line head 71 in a plan view. As shown in Fig. 7A, the light source 65 is disposed at one end of the line head 71 in the longitudinal direction DL in a plan view. The detection element 67 is disposed at the other end of the line head 71 in the longitudinal direction DL. In the embodiment of Fig. 7A, the frame 72 supporting the light source 65 and the detection element 67 moves back and forth in the short-side direction Dh when the discharge defect detection process is performed.

[0042] Alternatively, the light source 65 and the detection element 67 may be arranged relative to the line head 71 as follows. As shown in Fig. 7B, in a plan view, the light source 65 is arranged on one end side of the line head 71 in the short side direction Dh. The detection element 67 is arranged on the other end side of the line head 71 in the short side direction Dh. In the embodiment of Fig. 7B, the frame 72 supporting the light source 65 and the detection element 67 moves back and forth in the longitudinal direction DL when the discharge defect detection process is performed.

[0043] Next, FIGS. 8A and 8B are diagrams showing examples of the arrangement of light sources 65 and detecting elements 67 between one line head 71 and the other line head 71 that are adjacent to each other.

[0044] 8A and 8B, a plurality of line heads 71 ​​are arranged at predetermined intervals in the short-side direction Dh of the line head 71. A light source 65 and a detection element 67 are provided for each line head 71. In other words, the light source 65 and the detection element 67 are provided for one line head 71.

[0045] As shown in FIG. 8A , in a region between one line head 71 and another line head 71 adjacent to each other in the short-side direction Dh, a light source 65 corresponding to the one line head 71 and a detection element 67 corresponding to the other line head 71 are arranged side by side in the longitudinal direction DL of the line head 71. Here, in this example, in one of the two regions adjacent to each other in the short-side direction Dh, the light source 65 and the detection element 67 are arranged in this order from one end side of the line head 71 in the long-side direction DL. In contrast, in the other of the two regions adjacent to each other in the short-side direction Dh, the detection element 67 and the light source 65 are arranged in this order from one end side of the line head 71 in the long-side direction DL. Note that in FIGS. 8A and 8B and FIG. 14 described below, the light source 65 is illustrated in gray to facilitate understanding of the arrangement of the light source 65 relative to the detection element 67.

[0046] Alternatively, the light sources 65 and the detecting elements 67 between adjacent line heads 71 ​​may be arranged as follows: As shown in FIG. 8B , in a region between one line head 71 and the other line head 71 adjacent to each other in the short-side direction Dh, the light source 65 corresponding to the one line head 71 and the light source 65 corresponding to the other line head 71 are arranged side by side in the longitudinal direction DL of the line head 71. As a result, in one of the two regions adjacent to each other in the short-side direction Dh, the two light sources 65 are arranged side by side in the longitudinal direction DL of the line head 71. In contrast, in the other of the two regions adjacent to each other in the short-side direction Dh, the detecting element 67 corresponding to the one line head 71 and the detecting element 67 corresponding to the other line head 71 are arranged side by side in the longitudinal direction DL of the line head 71. As a result, in the other of the two regions adjacent to each other in the short-side direction Dh, the two detecting elements 67 are arranged side by side in the longitudinal direction DL of the line head 71.

[0047] As described above, according to the droplet ejection device 100, the light source 65 in the first position P1 irradiates the ink droplets ejected from the nozzle Nz with the laser light Lz as the first light, and the light source 65 in the second position P2 irradiates the ink droplets ejected from the same nozzle Nz as the nozzle Nz with the laser light Lz as the second light. Then, by detecting the first received light amount of the first light, it is possible to detect the presence or absence of ejected ink droplets and the volume of the ink droplets. Furthermore, by detecting the second received light amount of the second light, it is possible to detect whether the ink droplets whose presence has been detected are flying in a curved manner while overlapping with the optical axis La of the laser light Lz as the first light. In other words, it is possible to detect how far the ink droplets are flying in the direction of the optical axis La of the laser light Lz as the first light (in the depth direction of the optical axis). In this way, it is not possible to determine from the first received light amount alone whether the ink droplets are flying in a curved manner while overlapping with the optical axis La of the laser light Lz as the first light, but by using the second received light amount related to the second light, it is possible to calculate with high accuracy the amount of deflection of the ink droplets relative to their normal flight direction.

[0048] Furthermore, in this embodiment, the rotation center CR is located in the central region of the optical path LP between the light source 65 and the detection element 67. This allows the space required for the movement of the light source 65 and the detection element 67 to be saved.

[0049] Furthermore, in this embodiment, in plan view, the light source 65 is disposed on one end side of the longitudinal direction DL of the line head 71, and the detection element 67 is disposed on the other end side of the longitudinal direction DL of the line head 71. This makes it possible to irradiate the laser light Lz onto ink droplets ejected from all of the nozzles Nz constituting the nozzle rows in each ejection head 10 arranged along the longitudinal direction DL of the line head 71. This can shorten the total time required to detect ejection deflection for all of the nozzles Nz.

[0050] Furthermore, in this embodiment, the light source 65 may be disposed on one end side of the line head 71 in the short side direction Dh in plan view, and the detection element 67 may be disposed on the other end side of the line head 71 in the short side direction Dh. This makes it possible to shorten the optical path length of the laser light Lz irradiated from the light source 65, and therefore to narrow the beam diameter of the laser light Lz. This increases the energy density of the laser light Lz, and as a result, improves the signal-to-noise ratio.

[0051] Furthermore, in this embodiment, in the region between one line head 71 and another line head 71 adjacent to each other in the short-side direction Dh, the light source 65 corresponding to the one line head 71 and the detection element 67 corresponding to the other line head 71 are arranged side by side in the longitudinal direction DL of the line head 71. This makes it possible to achieve space saving in the short-side direction Dh of the line head 71 compared to when the light source 65 and the detection element 67 between the one line head 71 and the other line head 71 are arranged side by side in the short-side direction Dh of the line head 71.

[0052] Furthermore, in this embodiment, in one of the two regions adjacent to each other in the short-side direction Dh, two light sources 65 may be arranged side by side in the longitudinal direction DL of the line head 71. Then, in the other of the two regions adjacent to each other in the short-side direction Dh, two detecting elements 67 may be arranged side by side in the longitudinal direction DL of the line head 71. This makes it possible to achieve more space saving in the short-side direction Dh of the line head 71 than when two light sources 65 between one line head 71 and another line head 71 are arranged side by side in the short-side direction Dh of the line head 71, or when two detecting elements 67 between one line head 71 and another line head 71 are arranged side by side in the short-side direction Dh of the line head 71. Furthermore, arranging the light sources 65 in the same region and the detecting elements 67 in the same region leads to a reduction in noise.

[0053] (Second embodiment) A second embodiment of the present disclosure will be described. Fig. 9 is a diagram showing an example of the arrangement of the light source 65 and the detection element 67 relative to the nozzle surface NM. Fig. 10 is a diagram showing an example of the arrangement of the light source 65 and the detection element 67 relative to the transport direction Df.

[0054] 9 and 10, the nozzle surface NM has a long side Ls and a short side Ss. The light source 65 is disposed at one end of the nozzle surface NM in a direction parallel to the short side Ss. The detection element 67 is disposed at the other end of the nozzle surface NM in a direction parallel to the short side Ss. Alternatively, the light source 65 may be disposed at the other end and the detection element 67 may be disposed at the one end.

[0055] The light source 65 is disposed downstream in the transport direction Df of the print medium W. The detection element 67 is disposed upstream in the transport direction Df of the print medium W.

[0056] Next, Fig. 11 is a diagram showing the irradiation direction of laser light Lz from light source 65. Fig. 12 is a diagram showing an example of a light-shielding portion 80 provided between nozzle surface NM and optical axis La. Fig. 13 is a diagram showing another example of a light-shielding portion 80 provided between nozzle surface NM and optical axis La.

[0057] 11, the detection element 67 is disposed below the light source 65 with respect to the nozzle surface NM. In this case, all or part of the light source 65 may be disposed above the nozzle surface NM. The light source 65 irradiates the detection element 67 with laser light Lz so that the optical axis La faces obliquely downward with respect to the nozzle surface NM.

[0058] 12, the light source 65 and the detection element 67 are disposed below the nozzle surface NM. In this case, the light source 65 and the detection element 67 are disposed, for example, outside the nozzle surface NM in a plan view. Note that the light source 65 and the detection element 67 may also be disposed below the nozzle surface NM but inside the nozzle surface NM in a plan view.

[0059] Generally, ink droplets ejected from the ejection head 10 often fly straight for only a few millimeters in the ejection direction. For this reason, it is necessary to bring the optical axis La as close as possible to the nozzle surface NM. As a result, the laser light Lz from the light source 65 is reflected by the nozzle surface NM, generating reflected light, which is detected by the detection element 67. When the detection element 67 detects reflected light, the proportion of the laser light Lz that is blocked by the ink droplets out of the total amount of laser light Lz that enters the detection element 67 decreases. This makes it difficult to properly detect ejection defects.

[0060] 12, a light-shielding portion 80 is provided between the nozzle surface NM and the optical axis La of the laser light Lz from the light source 65. The light-shielding portion 80 is provided below the nozzle surface NM. In other words, the light-shielding portion 80 is disposed inside the nozzle surface NM in a plan view. The length of the light-shielding portion 80 in the direction parallel to the optical axis La can be set as appropriate.

[0061] 13, similar to FIG. 12, a light-shielding portion 80 is provided between the nozzle surface NM and the optical axis La of the laser light Lz from the light source 65, but the light-shielding portion 80 may be provided below the nozzle surface NM. In other words, the light-shielding portion 80 may be disposed outside the nozzle surface NM in a plan view.

[0062] Next, FIG. 14 is a diagram showing the position of the optical axis La of the light source 65 between one line head 71 and another line head 71 adjacent to each other in the short-side direction Dh of the line head 71. As shown in FIG.

[0063] 14, in an arrangement region Rp, which is a region between one line head 71 and another line head 71 adjacent to each other in the short-side direction Dh, a light source 65 corresponding to the one line head 71 and a detection element 67 corresponding to the other line head 71 are provided. Here, in this example, of the two arrangement regions Rp adjacent to each other in the short-side direction Dh, in one arrangement region Rp, the detection element 67 and the light source 65 are arranged in this order from one end side of the line head 71 in the longitudinal direction DL. In contrast, of the two arrangement regions Rp adjacent to each other in the short-side direction Dh, in the other arrangement region Rp, the light source 65 and the detection element 67 are arranged in this order from one end side of the line head 71 in the longitudinal direction DL.

[0064] In such a configuration, the optical axis La of the laser light Lz irradiated by the light source 65 in one arrangement area Rp and the optical axis La of the laser light Lz irradiated by the light source 65 in another arrangement area Rp adjacent to the one arrangement area Rp in the short direction Dh are offset from each other in a direction intersecting the optical axis La.

[0065] Fig. 15 is a diagram showing the irradiation timing of the laser light Lz in each unit. In Fig. 14, a combination of a light source 65 and a detection element 67 corresponding to one line head 71, the light source 65 in one arrangement region Rp and the detection element 67 in another arrangement region Rp adjacent to the one arrangement region Rp in the short direction Dh, is called a unit. Fig. 14 shows three units: a first unit UT1, a second unit UT2, and a third unit UT3.

[0066] 15, the control device 20 shifts the irradiation timing T1 of the laser light Lz emitted by the light source 65 of the first unit UT1, which is a light source 65 in one arrangement region Rp, relative to the irradiation timing T2 of the laser light Lz emitted by the light source 65 of the second unit UT2, which is a light source 65 in another arrangement region Rp. In this case, the control device 20 may make the irradiation timing of the laser light Lz emitted by the light source 65 of the third unit UT3 the same as or different from the irradiation timing T1.

[0067] As described above, in this embodiment, the light source 65 is disposed on one end side of the nozzle surface NM in a direction parallel to the short side Ss, and the detection element 67 is disposed on the other end side of the nozzle surface NM in a direction parallel to the short side Ss. This makes it possible to shorten the optical path length of the laser light Lz emitted from the light source 65, and therefore to narrow the beam diameter of the laser light Lz. This increases the energy density of the laser light Lz and improves the signal-to-noise ratio.

[0068] Generally, there is a lot of convection matter such as paper dust from the print medium W downstream in the transport direction Df, which can reduce the S / N ratio. While it is difficult to increase the detection sensitivity of the detection element 67, in this embodiment, the light source 65 is arranged downstream in the transport direction Df of the print medium W, and the detection element 67 is arranged upstream in the transport direction Df of the print medium W. This makes it possible to improve the S / N ratio by increasing the amount of light emitted by the light source 65 arranged downstream in the transport direction Df.

[0069] Furthermore, in this embodiment, the light source 65 irradiates the detection element 67 with laser light Lz such that the optical axis La faces obliquely downward relative to the nozzle surface NM. This can prevent the laser light Lz irradiated from the light source 65 from being reflected by the nozzle surface NM, thereby improving the signal-to-noise ratio at the detection element 67.

[0070] Furthermore, in this embodiment, the reflected light of the laser light Lz irradiated from the light source 65 and reflected by the nozzle surface NM is blocked by the light-shielding portion 80. This suppresses or prevents the reflected light from entering the detection element 67, thereby improving the signal-to-noise ratio of the detection element 67.

[0071] Furthermore, in this embodiment, the optical axis La of the laser light Lz irradiated by the light source 65 in one arrangement region Rp and the optical axis La of the laser light Lz irradiated by the light source 65 in another arrangement region Rp adjacent to the one arrangement region Rp in the short direction Dh are offset from each other in a direction intersecting the optical axis La. This makes it possible to suppress or prevent scattered light in one arrangement region Rp from being detected by the detecting element 67 in the other arrangement region Rp.

[0072] Furthermore, in this embodiment, the control device 20 shifts the irradiation timing T1 of the laser light Lz emitted by the light source 65 of the first unit UT1 relative to the irradiation timing T2 of the laser light Lz emitted by the light source 65 of the second unit UT2. This makes it difficult for the detecting elements 67 in one arrangement region Rp to detect scattered light caused by the light sources 65 in other arrangement regions Rp. This improves the signal-to-noise ratio of the detecting elements 67 in one arrangement region Rp. [Explanation of symbols]

[0073] 10 Discharge head 20 Control device 65 Light source 67 Detector element 68 Rotary Motor 69 Travel Motor 71 Line Head 72 frames 80 Light blocking section 100 Droplet discharge device CR rotation center Dd detection device Dh Short direction DL Longitudinal Dr Return direction Dt Outbound direction ID ink drops La optical axis LP optical path Ls Long side of nozzle surface Lz laser light NM nozzle surface Nz nozzle P1 1st posture P2 2nd posture Rp placement area Sh flight space Ss Short side of nozzle surface W Printing medium

Claims

1. a head having a nozzle surface with a plurality of nozzles that eject droplets onto a print medium; a light source that irradiates light toward a flight space in which droplets ejected from the nozzle fly, and a detection device that has a detection element that is disposed across the flight space from the light source and detects the light; a rotation device that rotates the detection device about a predetermined rotation center so that the irradiation direction of the light changes within a plane parallel to the nozzle surface; a moving device that moves the detection device in a predetermined forward direction and a backward direction; a control device; The control device a process of rotating the detection device with the rotation device about the rotation center as a base point so that an angle of the optical axis with respect to the head becomes a first angle, and setting the detection device in a first attitude; receiving a first amount of received light related to the first light detected by the detection element when the light source irradiates the droplets ejected from the nozzle into the flight space with light as the first light while the moving device moves the detection device in the first attitude in the forward direction; a process of rotating the detection device with the rotation device about the rotation center as a base point to set the detection device in a second attitude so that an angle of the optical axis with respect to the head becomes a second angle different from the first angle; receiving a second amount of received light of the second light detected by the detection element when the light source irradiates the droplets ejected into the flight space from the same nozzle as the nozzle with light as the second light while the movement device moves the detection device in the second attitude in the return direction; and calculating an amount of deflection of the droplet relative to a normal flight direction based on the first amount of received light and the second amount of received light.

2. The droplet ejection device according to claim 1 , wherein the center of rotation is in a central region of an optical path between the light source and the detection element.

3. 2. The droplet ejection device according to claim 1, wherein the light source is disposed on one end side of the head in the longitudinal direction, and the detection element is disposed on the other end side of the head in the longitudinal direction.

4. The droplet ejection device according to claim 1 , wherein the light source is disposed on one end side of the head in the lateral direction, and the detection element is disposed on the other end side of the head in the lateral direction.

5. The head is arranged at a predetermined interval in the short side direction of the head, The light source and the detection element are provided for each of the heads, 2. The droplet ejection device according to claim 1, wherein the light source corresponding to one head and the detection element corresponding to the other head are arranged side by side in the longitudinal direction of the heads between the heads.

6. The head is arranged at a predetermined interval in the short side direction of the head, The light source and the detection element are provided for each of the heads, A droplet ejection device as described in claim 1, wherein between one of the heads and another of the heads, the light source corresponding to the one head and the light source corresponding to the other head are arranged side by side in the longitudinal direction of the heads, or the detection element corresponding to the one head and the detection element corresponding to the other head are arranged side by side in the longitudinal direction of the heads.

7. the nozzle face has a long side and a short side; The droplet ejection device according to claim 1 , wherein the light source is disposed on one end side of the nozzle surface in the direction of the short side, and the detection element is disposed on the other end side of the nozzle surface in the direction of the short side.

8. The droplet ejection device according to claim 7 , wherein the light source is disposed downstream in a transport direction of the print medium, and the detection element is disposed upstream in the transport direction of the print medium.

9. the detection element is disposed below the light source with respect to the nozzle face, The droplet ejection device according to claim 1 , wherein the light source irradiates the light obliquely downward from the nozzle surface toward the detection element.

10. the light source and the detection element are disposed below the nozzle surface, The droplet ejection device according to claim 1 , further comprising a light blocking portion provided between the nozzle surface and the optical axis of the light from the light source.

11. The head is arranged at a predetermined interval in the short side direction of the head, The light source and the detection element are provided for each of the heads, the light source corresponding to the one head and the detection element corresponding to the other head are provided in an arrangement region that is a region between one of the heads and another of the heads; The droplet ejection device according to claim 4, wherein the optical axis of the light emitted by the light source in one of the arrangement areas and the optical axis of the light emitted by the light source in another arrangement area adjacent to the one of the arrangement areas are offset from each other in a direction intersecting the optical axis.

12. The head is arranged at a predetermined interval in the short side direction of the head, The light source and the detection element are provided for each of the heads, the light source corresponding to the one head and the detection element corresponding to the other head are provided in an arrangement region that is a region between one of the heads and another of the heads; The droplet ejection device according to claim 4 , wherein the control device shifts the timing of light emitted by the light source in one of the placement areas relative to the timing of light emitted by the light source in another placement area adjacent to the one placement area.

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