Droplet ejection device

Abstract

The present invention provides a droplet dispensing device that can reduce the total processing time for detecting dispensing defects. [Solution] The droplet dispensing device comprises a dispensing head having multiple nozzles, a light source that emits light toward the flight space, a light receiving unit that detects the amount of light received after the light emitted from the light source has passed through the flight space, and a control device. The control device performs a first reference waveform acquisition process that acquires a reference waveform of the signal for a droplet dispensed by one nozzle as a first reference waveform, a detection waveform process that acquires a detected waveform of the signal for a droplet dispensed by one nozzle, a second reference waveform acquisition process which is performed after the first reference waveform acquisition process and acquires a reference waveform of the signal for a droplet dispensed by a nozzle other than the first nozzle as a second reference waveform, and a first calculation process which is performed in parallel with the second reference waveform acquisition process and calculates the correlation between the first reference waveform and the detected waveform.

Description

Technical Field

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

Background Art

[0002] Conventionally, a liquid ejection failure detection device including a discharge head having nozzles, a light emitting element, and a light receiving unit has been known (Patent Document 1). The light receiving unit has a light receiving element and a current-voltage conversion circuit unit. The light receiving element outputs a current corresponding to the intensity of the received light. The current-voltage conversion circuit unit converts the current output by the light receiving element into a voltage and outputs it. Waveform data is obtained based on the output voltage by the current-voltage conversion circuit unit, and ejection failure is detected based on a predetermined feature amount in the waveform data.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the detection process of ejection failure, a process (correlation process) for determining ejection failure of nozzles based on the consistency between a reference waveform which is a predicted waveform and a detection waveform based on an output signal from a light receiving element is known. However, there is a problem that the amount of calculation in the detection of ejection failure increases because the reference waveform is different for each nozzle and the reference waveform needs to be updated due to variations in the relative position of the nozzle with respect to the optical axis of the light emitted from the light emitting element.

[0005] Therefore, an object of the present disclosure is to provide a droplet ejection device capable of shortening the total time of arithmetic processing in the detection of ejection failure.

Means for Solving the Problems

[0006] The droplet ejection device of the present disclosure comprises: an ejection head having a plurality of nozzles for ejecting droplets onto a printing medium; a light source that emits light toward a flight space in which the droplets ejected from the nozzles fly; a light receiving unit that detects the amount of light received after the light emitted from the light source has passed through the flight space and outputs a signal; and a control device, the control device performing: a first reference waveform acquisition process that acquires a reference waveform of the signal for the droplet ejected by one of the nozzles as a first reference waveform; a detection waveform process that acquires a detection waveform of the signal for the droplet ejected by one of the nozzles; a second reference waveform acquisition process that is performed after the first reference waveform acquisition process and acquires a reference waveform of the signal for the droplet ejected by a nozzle other than the one nozzle as a second reference waveform; and a first calculation process that is performed in parallel with the second reference waveform acquisition process and calculates the correlation between the first reference waveform and the detection waveform.

[0007] According to this disclosure, the first calculation process is executed in parallel with the second reference waveform acquisition process. This reduces the total calculation time for detecting ejection defects compared to the case where the first calculation process is not executed in parallel with the second reference waveform acquisition process. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide a droplet dispensing device that can shorten the total processing time for detecting dispensing defects. [Brief explanation of the drawing]

[0009] [Figure 1] This is a plan view showing a droplet dispensing device according to one embodiment of the present disclosure. [Figure 2] Figure 1 is a cross-sectional view showing the configuration of the discharge head. [Figure 3] Figure 1 is a block diagram showing the components of a printing apparatus equipped with a droplet ejection device. [Figure 4] This is a block diagram showing the functional configuration of the control device in Figure 3. [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 an explanatory diagram illustrating an example of how multiple tasks are executed in parallel during the ejection failure detection process. [Figure 7] This is a diagram showing the beam waist portion of a laser beam. [Figure 8] Figure 8A shows the illuminance distribution including the illuminance (central illuminance) at the position of the optical axis of the laser beam, and Figure 8B shows the illuminance distribution including the illuminance at a position a certain distance away from the optical axis in the radial direction of the laser beam. [Figure 9] Figure 8B shows the dimensions of the laser beam in a direction perpendicular to the radial direction of the laser beam. [Figure 10] This is an explanatory diagram illustrating an example of how multiple tasks are executed in parallel during the ejection failure detection process. [Figure 11] This is an explanatory diagram illustrating an example of how multiple tasks are executed in parallel during the ejection failure detection process. [Modes for carrying out the invention]

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

[0011] Figure 1 is a perspective view showing a droplet ejection device 100 according to one embodiment of the present disclosure. Figure 2 is a cross-sectional view showing the configuration of the ejection head 10 in Figure 1. Figure 3 is a block diagram showing the components of a printing apparatus 1 equipped with the droplet ejection device 100 of Figure 1. Figure 4 is a block diagram showing the functional configuration of the control device 20 in Figure 3. In Figures 1 and 2, 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 described later, the second direction Df is the direction of transport of the printing medium W 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 Figures 1 and 3, the droplet ejection device 100 includes, for example, two ejection heads 10 (10A, 10B), two ultraviolet irradiation devices 40 (40A, 40B), a carriage 3 on which the ejection heads 10 and ultraviolet irradiation devices 40 are mounted, a storage tank 62, a pair of guide rails 63, and a controller unit 19 including a control device 20. In this embodiment, an inkjet head that ejects ultraviolet-curable ink droplets Id (Figure 5 below) is exemplified as the ejection head 10. However, the form of the ejection head 10 is not limited. If the ejection head 10 ejects ordinary ink droplets that are not ultraviolet-curable ink droplets, the ultraviolet irradiation devices 40 are not required. In this embodiment, ink droplets Id correspond to liquid droplets.

[0013] The carriage 3 is supported by a pair of guide rails 63 that extend in the direction of movement Ds, and reciprocates along the guide rails 63 in the direction of movement Ds. As a result, the two discharge heads 10 (10A, 10B) and the two ultraviolet irradiation devices 40 (40A, 40B) reciprocate in the direction of movement Ds. The discharge heads 10 are also connected to the storage tank 62 via tubes 62a.

[0014] In this embodiment, the ejection head 10A ejects ink droplets Id of each color of yellow (Y), magenta (M), cyan (C), and black (K), which are collectively referred to as color inks. By ejecting the ink droplets Id of the above four colors onto the printing medium W supported on a platen (not shown), a color image is printed on the printing medium W. On the other hand, the ejection head 10B ejects, for example, ink droplets Id of white (W) and clear (Cr). When printing a color image on, for example, a fabric as the printing medium W, in order to reduce the influence on the color and material of the fabric, ink droplets Id of white ink are ejected first as the base ink, and ink droplets Id of color ink are ejected onto the ink droplets Id of the white ink. Also, the ink droplets Id of the clear ink are ejected when imparting gloss or protecting the printed portion.

[0015] Ink is stored in the storage tank 62. The storage tank 62 is provided for each type of ink. Six storage tanks 62 are provided, for example, and store black, yellow, cyan, magenta, white, and clear inks, respectively.

[0016] The droplet ejection device 1a further includes a purge unit 50 and a receiving unit 54. The receiving unit 54 is disposed at one end side in the moving direction Ds of the pair of guide rails 63 so as to overlap the moving region of the carriage 3. The purge unit 50 is disposed at the other end side in the moving direction Ds of the pair of guide rails 63 so as to overlap the moving region of the carriage 3.

[0017] 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 nozzle surface NM (Figure 2), described later, is separated from the cap 51. On the other hand, in the suction position, the nozzle 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 2). The receiving unit 54 receives ink droplets Id discharged from the discharge head 10 by the flushing process. The ink discharged by the purging process and the ink discharged by the flushing process are treated as waste liquid.

[0018] As shown in Figure 2, 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 open on its lower surface, the nozzle 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.

[0019] The flow channel 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 is connected to the diaphragm 155.

[0020] 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.

[0021] 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.

[0022] The nozzle 121 is formed by penetrating the nozzle plate 146 in the stacking direction. On the nozzle 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.

[0023] 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.

[0024] 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. This creates a damper space 147b as a buffer space between the manifold 122 and the nozzle plate 146.

[0025] 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.

[0026] 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 in the direction of ink supply.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] The diaphragm 155 is laminated on the seventh flow path plate 154 and covers the upper end opening of the pressure chamber 128.

[0032] 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.

[0033] The individual electrodes 163 are electrically connected to the head driver IC 32 (Figure 3). The head driver IC 32 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 maintained 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.

[0034] 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.

[0035] The printing device 1 is, for example, an inkjet printer capable of printing on a three-dimensional object, the printing medium W. The printing device 1 may also be an inkjet printer capable of printing only on paper. As shown in Figure 3, the printing device 1 includes an operation key 4, a display unit 5, and a reading device 26. The droplet ejection device 100 includes motor driver ICs 30, 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, a light source 65, and a detection element 67. In this embodiment, the detection element 67 corresponds to a light receiving unit.

[0036] The controller unit 19 includes, for example, 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, 35-38 and the display unit 5.

[0037] 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 various information.

[0038] The ASIC25 is connected to motor driver ICs 30 and 31, head driver IC 32, irradiation device driver IC 35, purge driver IC 36, light source driver IC 37, and 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 controls each driver IC 30-32 and 35-38 based on the image recording command. The control device 20 moves the platen in the transport direction Df by driving the transport motor 33 with the motor driver IC 30. As a result, the printing medium W supported by the platen is transported in the transport direction Df. 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. As a result, the ejection head 10 moves in the movement direction Ds. The carriage motor 34 is equipped with an encoder to detect the rotation speed of the carriage motor 34.

[0039] The control device 20 converts image data acquired from an external device into ejection data for ejecting ink droplets Id onto the printing medium W. 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 the 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 controls the laser light emission operation of the light source 65 using the light source driver IC 37 and also receives signals from the detection element 67.

[0040] As shown in Figure 4, the control device 20 has a calculation unit 20a. The amount of light received from the laser light emitted from the light source 65 is detected by the detection element 67. The detection element 67 outputs a signal corresponding to the detected amount of light received to the calculation unit 20a of the control device 20. The calculation unit 20a calculates the correlation between the predicted waveform and the waveform detected by the detection element 67. Based on the signal after the calculation, the control device 20 determines whether or not there is a discharge defect.

[0041] Figure 5 shows the process of irradiating a flying ink droplet Id, ejected from the ejection head 10, with laser light Lz.

[0042] As shown in Figure 5, the light source 65 emits laser light Lz in a specific wavelength range. More specifically, the light source 65 irradiates the laser light Lz towards the flight space Sh in which the ink droplet Id ejected from the ejection head 10 flies. In this embodiment, the laser light Lz corresponds to light.

[0043] The light source 65 is positioned on one side of the position of the discharge head 10 with reference to the optical axis DL of the optical axis La of the laser light Lz emitted from the light source 65. Examples of the light source 65 include light-emitting diodes (LEDs) and semiconductor lasers (LDs). The 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 light Lz emitted from the 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. One or more lenses may be provided in addition to lens 65c. The light source 65 is supported by a frame 71 that extends in the optical axis DL of the laser light Lz.

[0044] On the other hand, the detection element 67 is positioned on the other side of the optical axis direction DL, with reference to the position of the discharge head 10. The detection element 67 generates a current based on the received laser light Lz and outputs the current signal to a current-voltage conversion circuit (not shown). The current-voltage conversion circuit converts the current signal from the detection element 67 into a voltage signal and outputs the voltage signal to an amplification circuit (not shown). The amplification circuit amplifies the voltage signal from the current-voltage conversion circuit and outputs it to the control device 20. The detection element 67 is supported by the frame 71, similar to the light source 65.

[0045] In the above configuration, the laser beam Lz emitted from the light source 65 passes through the lens 65c and is then ejected from the ejection head 10, irradiating the ink droplet Id in flight in the flight space Sh. The detection element 67 detects the amount of light received after the laser beam Lz emitted from the light source 65 has passed through the flight space Sh. The control device 20 uses the signal output from the detection element 67 to perform ejection failure detection processing. In this ejection failure detection processing, ejection failures such as abnormal velocity of ink droplet Id, abnormal volume of ink droplet Id, and distortion of ink droplet Id are detected. Distortion means that the ink droplet Id flies in a direction different from the normal flight direction.

[0046] Next, the discharge failure detection process in this embodiment will be described. In the discharge failure detection process, a discharge failure of the nozzle 121 is determined based on a correlation process that acquires the agreement between a predicted waveform (reference waveform) and the detection waveform by the detection element 67. Thus, a predicted waveform is required for the correlation process. Since the predicted waveform is different for each nozzle 121, a predicted waveform is required for each nozzle 121. However, the relative position of the nozzle 121 with respect to the optical axis La of the laser beam Lz varies due to control errors in braking against the inertial force when the carriage 3 stops from moving, etc. Therefore, the predicted waveform needs to be updated each time, which increases the calculation time. In addition, since the beam illuminance changes depending on the position in the direction of the optical axis La of the laser beam Lz, a predicted waveform is required every time the nozzle position in the optical axis direction changes. In this case, since there are many nozzles, if the predicted waveform for each position is stored in memory in advance, the memory capacity will be large, and the predicted waveform will need to be updated each time. Therefore, in this embodiment, multiple tasks are executed in parallel in the step of the discharge failure detection process. This will be explained in detail below.

[0047] Figure 6 is an explanatory diagram showing that multiple tasks are executed in parallel during the ejection failure detection process. Figure 7 is a diagram showing the beam waist BW of the laser beam Lz. Figure 8A is a diagram showing the illuminance distribution including the illuminance (center illuminance) I0 at the optical axis La of the laser beam Lz, and Figure 8B is a diagram showing the illuminance distribution including the illuminance I0' at a position a certain distance x in the radial direction related to the horizontal direction of the laser beam Lz from the optical axis La. Figure 9 is a diagram showing the dimension y of the laser beam Lz in a direction perpendicular to the radial direction of the laser beam Lz shown in Figure 8B. In Figure 6, channel 2 is the channel adjacent to channel 1 in the movement direction Ds, and other channels are assigned ordinal numbers in the same manner. The same applies to Figures 10 and 11 described later.

[0048] As shown in Figure 6, in step 1, the control device 20 performs process A1 to update the predicted waveform for the nozzle 121 of channel 1.

[0049] The following describes the predicted waveform. As shown in Figure 7, the laser light Lz emitted from the light source 65 has a beam waist BW, which is the part where the optical diameter is smallest in the optical axis direction DL. In Figure 7, z is the position in the optical axis direction DL. The radius of the cross-section in this beam waist BW is defined as the beam waist radius ω0, and z at this position is defined as 0.

[0050] The laser beam Lz exhibits an intensity distribution in a plane perpendicular to its optical axis DL that closely resembles a Gaussian distribution. Considering this, the illuminance I(r) [mW / cm²] at a distance r from the optical axis La in the radial direction of the laser beam Lz can be calculated as follows: 2 The illuminance can be calculated using the following formula 1, where the central illuminance is I(0)[mW / cm2], the optical power is P[mW], the laser beam radius (beam diameter) at a distance r is ω(z)[cm], and the optical wavelength is λ[cm]. However, I(0)[mW / cm2] in formula 1 is expressed by the following formula 2, and ω(z)[cm] in formula 1 is expressed by the following formula 3.

[0051]

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[0052]

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[0053]

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[0054] In reality, as shown in Figure 8A, it is difficult for the ejected ink droplet Id to fly to a position that coincides with the optical axis La of the laser beam Lz. This is because, as mentioned above, due to control errors in braking against the inertial force when the carriage 3 stops moving, the flight position of the ink droplet Id is shifted by a certain distance in the radial direction (radial direction relative to the horizontal direction) of the laser beam Lz with respect to the optical axis La, as shown in Figure 8B. Note that the z direction changes depending on the nozzle position, but if the ejection nozzle is known, the z direction in the figure with respect to the beam waist position z=0 is known and can be calculated according to equation 3 using equation 1 and equations 7 and 8 described later.

[0055] Consider equation 1 in the case of Figure 8B. As shown in Figure 9, when the ink droplet Id is flying at a position where it is offset by a distance x in the radial direction of the laser beam Lz from the optical axis La, and at a height y, then, according to the Pythagorean theorem, r 2 =x 2 +y 2 Since the above holds true, the illuminance I(r)=I(x,y) is expressed by the following equation 4 based on the above equation 1. In this case, the control device 20 acquires the position of the nozzle 121 of channel 1. Specifically, the control device 20 calculates the positional deviation amount based on the positional target value of the nozzle 121 of channel 1 and the value detected by the encoder of the carriage motor 34, and acquires the calculated positional deviation amount as the above distance x, which is the deviation amount from the optical axis La.

[0056]

number

[0057] Here we consider the relationship between the ink droplet position and the detected voltage V. The fluctuation amount ΔV of the detected waveform decreases in proportion to the illuminance I(r) at the ink droplet as it passes along the optical axis La. Therefore, when the velocity of the ink droplet is v, ΔV = K × I(r). Also, the ink droplet moves in the y direction according to the relationship y = v × t. Thus, when the velocity of the ink droplet Id is v, the following equation holds true for the fluctuation amount of the detected waveform: ΔV = K × I(y) = K × I(v × t). Let this equation be Equation 5. Note that K is a constant in Equation 5 and in Equations 6 and 7 described later.

[0058] Taking into account equations 1, 3, 4, and 5 above, the following equation 6 is obtained.

[0059]

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[0060] For the predicted waveform A(t), using the waveform ΔV(t) during normal discharge, i.e., when there are no abnormalities such as distortion or velocity abnormalities, the equation A(t) = ΔV(t) holds true. Therefore, the predicted waveform A(t) is expressed by the following equation 7.

[0061]

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[0062] As described above, the control device 20 obtains a predicted waveform A(t) in process A1 of step 1 based on the above formula 7. In this embodiment, the predicted waveform for the nozzle 121 of channel 1 is an example of a first reference waveform, and the process of acquiring the first reference waveform is an example of a first reference waveform acquisition process.

[0063] The control device 20 then performs detection waveform processing to acquire the detection waveform g(t) of the signal from the detection element 67 regarding the ink droplet Id ejected by the nozzle 121 of channel 1. In this case, the control device 20 emits laser light Lz from the light source 65 toward the flight space Sh, and ejects the ink droplet Id from the nozzle 121 of channel 1 of the ejection head 10 toward the laser light Lz.

[0064] Next, similar to process A1 described above, the control device 20 executes process A2 in step 2 to update the predicted waveform for the nozzle 121 of channel 2. In this embodiment, the predicted waveform for the nozzle 121 of channel 2 is an example of a second reference waveform, and the process of acquiring this second reference waveform is an example of a second reference waveform acquisition process.

[0065] Here, in step 2, the control device 20 executes process B1, which calculates the correlation between the predicted waveform A(t) for channel 1 and the detected waveform g(t) for channel 1, in parallel with the above process A2. That is, the control device 20 executes multiple tasks in step 2. In process B1, the control device 20 calculates the correlation using the following formula 8-1 or formula 9-1. The control device 20 may use the following formula 8-2 instead of formula 8-1, and the following formula 9-2 instead of formula 9-1. In formulas 8-1, 8-2 and formulas 9-1, 9-2, τ is the delay time, and in formulas 8-2 and 9-2, m is the number of data to be calculated, and tk represents the time of the k-th data.

[0066]

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[0067]

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[0068]

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[0069]

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[0070] The calculation unit 20a performs calculations based on the above formula 8-1 or formula 9-1, etc. The control device 20 determines whether or not there is a discharge defect based on the signal after the calculation.

[0071] Next, in step 3, similar to step 2, the control device 20 executes process A3 to update the predicted waveform for the nozzle 121 of channel 3, and in parallel with process A3, executes process B2 to calculate the correlation between the predicted waveform A(t) for channel 2 and the detected waveform g(t) for channel 2. In other words, the control device 20 performs multiple tasks in step 3. The control device 20 also performs similar processes in steps 4 and beyond.

[0072] As described above, the control device 20 acquires a predicted waveform A(t), which is a reference waveform, according to the position of each nozzle 121. The control device 20 also executes process An, which updates the predicted waveform for a predetermined channel, and process Bn, which calculates the correlation based on the predicted waveform, in the order of process An and process Bn, and executes process Bn and process An+1 in parallel at the same step. The above n is a natural number, and the same applies hereafter.

[0073] The control device 20 may perform multiple tasks in each step as shown below. Figure 10 is an explanatory diagram illustrating another example of multiple tasks being executed in parallel during the discharge failure detection process step. Figure 11 is an explanatory diagram illustrating yet another example of multiple tasks being executed in parallel during the discharge failure detection process step.

[0074] As shown in Figure 10, similar to Figure 6 described above, in step 1A, the control device 20 executes process A1, which calculates the correlation between the predicted waveform A(t) for channel 1 and the detected waveform g(t) for channel 1. In step 2A, the control device 20 executes process A2, which calculates the correlation between the predicted waveform A(t) for channel 2 and the detected waveform g(t) for channel 2. In this embodiment, process A2 is an example of a second calculation process.

[0075] If the calculation result of process A1 is an abnormal value, the control device 20 executes the detailed calculation processes B1 and B2 described below in parallel with process A2. In other words, the control device 20 executes multiple tasks in step 2A.

[0076] In detailed calculation process B1, the control device 20 changes the constant K in the above-mentioned equation 7, which is the formula for calculating the predicted waveform A(t), in order to change the amplitude of the waveform, and calculates the correlation between the predicted waveform based on this change (i.e., the predicted waveform with changed amplitude) and the detected waveform for channel 1. In detailed calculation process B2, the control device 20 sets the above-mentioned y to an arbitrary value in order to change the signal width of the waveform, and calculates the correlation between the predicted waveform based on this setting (i.e., the predicted waveform with changed signal width) and the detected waveform for channel 1.

[0077] The control device 20 performs a process (identification process) to determine whether or not there is a discharge defect with respect to one nozzle 121 based on the calculation results in processes B1 and B2. Specifically, if the calculation result in process B1 is an abnormal value, the control device 20 determines that there is an abnormal volume or distortion of the ink droplet Id as described above. Also, if the calculation result in process B2 is an abnormal value, the control device 20 determines that there is an abnormal velocity of the ink droplet Id as described above. The control device 20 performs the same process in steps 3A and later.

[0078] Furthermore, the control device 20 may execute a part of the above-described specific processing in parallel with the correlation calculation processing that is performed for the other nozzles 121 after the specific processing, as described below.

[0079] As shown in Figure 11, in step 1B, the control device 20 executes process A1, which calculates the correlation between the predicted waveform A(t) for channel 1 and the detected waveform g(t) for channel 1. In step 2B, the control device 20 executes process A2, which calculates the correlation between the predicted waveform A(t) for channel 2 and the detected waveform g(t) for channel 2. If the calculation result of process A1 is an abnormal value, the control device 20 executes process B1, which is a detailed calculation for process A1, in parallel with process A2, as shown in Figure 10 above.

[0080] Furthermore, in step 3B, the control device 20 executes process A3, which calculates the correlation between the predicted waveform A(t) for channel 3 and the detected waveform g(t) for channel 3. If the calculation result of process A2 is an abnormal value, the control device 20 executes process B2, which is a detailed calculation for process A2, in parallel with process A3. In addition, in step 4B, the control device 20 executes process A4, which calculates the correlation between the predicted waveform A(t) for channel 4 and the detected waveform g(t) for channel 4.

[0081] Here, typically, the time required for process B1 and process B2 is longer than the time required for process A2. Therefore, as shown in Figure 11, the control device 20 interrupts process B1 as soon as process A2 is completed. Similarly, the control device 20 interrupts process B2 as soon as process A3 is completed.

[0082] The control device 20 then resumes the interrupted processes B1 and B2 in the next process An+1, which is executed if the calculation result of process An is not an abnormal value. Specifically, in the example in Figure 11, the control device 20 resumes the interrupted processes B1 and B2 in parallel with process A4 in step 4B, the next step after step 3B in which process A3, whose calculation result was not an abnormal value, is performed. In this way, in step 4B, the control device 20 executes multiple tasks, process A4 and processes B1 and B2.

[0083] As described above, in the droplet dispensing device 100 of this embodiment, the control device 20 executes process An, which updates the predicted waveform for a predetermined channel, and process Bn, which calculates the correlation based on the predicted waveform, in the order of process An and process Bn, and executes process Bn and process An+1 in parallel in the same step. As a result, the total time of calculation processing for detecting dispensing defects can be shortened compared to the case where process Bn and process An+1 are not executed in parallel in the same step.

[0084] Furthermore, in this embodiment, the control device 20 acquires a predicted waveform A(t), which is a reference waveform, according to the position of each nozzle 121. This improves the accuracy of the discharge defect detection process.

[0085] Furthermore, in the embodiment shown in Figure 10 of this model, the control device 20 performs a computationally intensive identification process, which determines whether or not there is a discharge defect with respect to one nozzle 121, in parallel with a process that calculates the correlation between a predicted waveform A(t) for a predetermined channel and a detected waveform g(t) for the same predetermined channel. This reduces the total computation time for detecting discharge defects compared to the case where the identification process is not performed in parallel with the above computation process.

[0086] Furthermore, in the embodiment shown in Figure 11 of this model, a portion of a specific computationally intensive process is executed in parallel with subsequent computational processes (processes that calculate the correlation between a predicted waveform A(t) for a predetermined channel and a detected waveform g(t) for the same predetermined channel). This distributes the computation in the specific process. As a result, an increase in computation time caused by the concentration of computation in the specific process can be avoided.

[0087] In addition, if a discharge defect related to the nozzle 121 is detected during the specific processing of the above embodiment, the drive waveform for the nozzle 121 may be changed.

[0088] Furthermore, in the embodiment shown in Figure 11 of the above-described embodiment, it is assumed that the frequency of abnormal values ​​in the calculation result of the correlation between the predicted waveform A(t) for a predetermined channel and the detected waveform g(t) for the same predetermined channel is low (less than a certain number of times). [Explanation of symbols]

[0089] 10 Discharge heads 20 Control device 65 Light source 67 detection elements 100 Droplet discharge device 121 Nozzles Id Inkdrop Lz laser light Sh flight space W Printing medium

Claims

1. A dispensing head having multiple nozzles for dispensing droplets onto the printing medium, A light source that emits light toward the flight space in which the droplet ejected from the nozzle is flying, A light receiving unit that detects the amount of light received after the light emitted from the light source has passed through the flight space and outputs a signal, A control device is provided, The control device is A first reference waveform acquisition process that acquires the reference waveform of the signal for the droplet discharged by the nozzle as a first reference waveform, A detection waveform processing method is used to obtain the detection waveform of the signal for the droplet ejected by the first nozzle, A process performed after the first reference waveform acquisition process, the second reference waveform acquisition process which acquires a reference waveform of the signal for the droplet discharged by a nozzle other than the first nozzle as a second reference waveform, A droplet dispensing device that performs a process in parallel with the second reference waveform acquisition process, the first calculation process which calculates the correlation between the first reference waveform and the detected waveform.

2. The control device is A position acquisition process to acquire the position of each nozzle, The droplet dispensing device according to claim 1, which performs a reference waveform acquisition process to acquire the reference waveform corresponding to each nozzle according to the position of each nozzle.

3. The control device is A second calculation process for calculating the correlation for the other nozzles, The droplet dispensing apparatus according to claim 1, comprising: a process executed in parallel with the second calculation process, which determines whether or not there is a dispensing defect with respect to one nozzle based on the calculation result of the first calculation process.

4. The droplet dispensing device according to claim 3, wherein the control device performs a part of the specific processing for one nozzle in parallel with the second calculation processing performed for the other nozzle after the specific processing.

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