JP2023069168A - Droplet discharge device - Google Patents

Abstract

To provide a droplet discharge device that can detect discharge abnormality before discharge failure occurs.SOLUTION: A droplet discharge device includes: a discharge head for discharging droplets on a medium to be printed; a light source which irradiates a flying droplet after being discharged from the discharge head until it impacts on the medium to be printed, with light; a detection device which is movable in an optical axis direction of light in order to detect refracted light that is light emitted from the light source and having passed through a flying droplet; and a control device. The control device causes the light source to radiate light, and causes the detection device to scan in the optical axis direction, in a state that droplets are continuously discharged by the discharge head, in order to calculate a volume of a droplet on the basis of an amount of refracted light detected by the detection device when the detection device is caused to scan.SELECTED DRAWING: Figure 5

Description

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

Conventionally, there is a technology for detecting defective nozzles that do not eject ink. For example, Japanese Patent Application Laid-Open No. 2002-200000 discloses a technique for detecting an ejection failure nozzle using a laser. In the technique of Patent Document 1, first, an ejection pattern for ejecting droplets from desired nozzles is selected, and the ejected droplets are detected by a detection mechanism based on the ejection pattern. Then, the defective nozzle is specified based on the first output signal assumed to be output by the detection mechanism and the second output signal actually output by the detection mechanism.

JP-A-2004-275801

However, the piezoelectric element deteriorates with driving time in the stage prior to the ejection failure of the nozzle, and this may cause the volume of the ink droplet to change. As a result, the ejection accuracy of each nozzle is lowered, and there is a possibility that the desired image quality cannot be obtained.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a liquid droplet ejection apparatus capable of detecting an ejection abnormality before an ejection failure occurs.

A droplet ejection device according to the present invention includes an ejection head that ejects droplets onto a print medium, and a light source that irradiates the droplets in flight after they are ejected from the ejection head until they land on the print medium. an irradiating light source, and a detection device configured to be movable in the optical axis direction of the light and detecting refracted light, which is the light after the light emitted from the light source has passed through the flying droplet. and a control device, wherein the control device causes the light source to irradiate the light in a state in which the droplets are continuously ejected from the ejection head, and the detection device is moved in the optical axis direction. The volume of the droplet is calculated based on the light amount of the refracted light detected by the detection device when the detection device is scanned.

According to the present invention, by calculating the droplet volume, it is possible to determine whether or not the piezoelectric element has deteriorated in the stage prior to the ejection failure of the nozzle. As a result, it is possible to perform correction for adjusting the volume of the ink droplet based on the determination result. As a result, it is possible to prevent the ejection accuracy of each nozzle from deteriorating, and thus to obtain the desired image quality.

According to the present invention, it is possible to provide a droplet ejection device capable of detecting an ejection abnormality before an ejection failure occurs.

1 is a plan view showing a schematic configuration of a droplet ejection device; FIG. 2 is a cross-sectional view showing the configuration of an ejection head in the droplet ejection device of FIG. 1; FIG. 2 is a block diagram showing the configuration of the droplet discharge device of FIG. 1; FIG. FIG. 4 is a diagram showing how ink droplets ejected from an ejection head and in flight are irradiated with a laser beam. 5 is an enlarged view of a region indicated by a broken line in FIG. 4; FIG. It is a top view which shows arrangement|positioning of a light source and a detection apparatus. (a) to (c) are diagrams showing each ejection pulse in an ejection waveform before correction and each ejection pulse in an ejection waveform after correction. 4 is a flowchart showing processing after calculating the volume of an ink droplet;

DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid droplet ejection device according to an embodiment of the present invention will be described below with reference to the drawings. The droplet discharge device described below is merely one embodiment of the present invention. Therefore, the present invention is not limited to the following embodiments, and additions, deletions, and modifications can be made without departing from the scope of the present invention.

(First embodiment)
As shown in FIG. 1, the droplet ejection device 10 of the present embodiment ejects ink droplets as an example of droplets, and includes a storage tank 12, a carriage 16, an ejection head 20, a pair of transport rollers 15, A pair of guide rails 17 and a sub-tank 18 are provided. Note that the print medium W is placed on a platen (not shown) in the droplet ejection device 10 .

An ejection head 20 is mounted on the carriage 16 . The carriage 16 is supported by a pair of guide rails 17 extending in the main scanning direction perpendicular to the transport direction of the print medium W, and reciprocates along the guide rails 17 in the main scanning direction. As a result, the ejection head 20 reciprocates in the main scanning direction. Further, four sub-tanks 18 are mounted on the carriage 16, for example. Each sub-tank 18 is connected to the corresponding storage tank 12 via a tube.

A pair of transport rollers 15 are arranged parallel to each other along the main scanning direction. The transport roller 15 rotates when a transport motor (not shown) is driven, thereby transporting the print medium W on the platen in the transport direction.

Ink is stored in the storage tank 12 . The storage tank 12 is connected to the ejection head 20 via an ink flow path so as to supply ink to the ejection head 20 . A storage tank 12 is provided for each type of ink. For example, four storage tanks 12 are provided, and black, yellow, cyan, and magenta inks are stored respectively.

The ejection head 20 moves in the main scanning direction perpendicular to the transport direction. As shown in FIG. 2, the ejection head 20 has a plurality of nozzles 21 for ejecting ink. The ejection head 20 has a laminate of a flow path forming body and a volume changing portion. A liquid channel is formed in the inside of the channel forming body, and a plurality of nozzle holes 21a are provided in a nozzle surface 40a, which is the lower surface of the channel forming body. Further, the volume changing section is driven to change the volume of the liquid channel. At this time, the meniscus vibrates in the nozzle hole 21a and an ink droplet is ejected.

As shown in FIG. 2, the flow path forming body of the ejection head 20 is a laminate of a plurality of plates, and the volume changing section includes a vibrating plate 55 and an actuator (piezoelectric element) 60 . An insulating film 56 is connected on the diaphragm 55 , and a common electrode 61 to be described later is connected on the insulating film 56 .

The plurality of plates are nozzle plate 46, spacer plate 47, first channel plate 48, second channel plate 49, third channel plate 50, fourth channel plate 51, and fifth channel plate in order from the bottom. 52, a sixth channel plate 53, and a seventh channel plate 54 are stacked. The first channel plate 48 , the second channel plate 49 , the third channel plate 50 , the fourth channel plate 51 , and the fifth channel plate 52 constitute the manifold plate 44 .

Each plate is formed with holes and grooves of various sizes. A plurality of nozzles 21, a plurality of individual flow paths 64, and a manifold 22 are formed as liquid flow paths by combining holes and grooves inside the flow path forming body in which each plate is laminated.

The nozzles 21 are formed so as to penetrate the nozzle plate 46 in the stacking direction. On the nozzle surface 40a of the nozzle plate 46, a plurality of nozzle holes 21a, which are the tips of the nozzles 21, are arranged in the arrangement direction to form a nozzle row. The arrangement direction is a direction orthogonal to the stacking direction.

The manifold 22 supplies ink to a later-described pressure chamber 28 to which an ink ejection pressure is applied. The manifold 22 extends in the array direction and is connected to one end of each of the plurality of individual channels 64 . That is, the manifold 22 functions as a common flow path for ink. The manifold 22 is formed by a through hole penetrating through the first to fourth channel plates 48 to 51 in the stacking direction and a recess recessed from the lower surface of the fifth channel plate 52 overlapping in the stacking direction.

The nozzle plate 46 is arranged below the spacer plate 47 . The spacer plate 47 has a recess 45 in which a thin portion forming a damper portion 47a and a damper space 47b are formed by recessing in the thickness direction of the spacer plate 47 from the nozzle plate 46 side surface by, for example, half-etching. . With such a configuration, a damper space 47b is formed between the manifold 22 and the nozzle plate 46 as a buffer space.

A supply port 22a communicates with the manifold 22 . The supply port 22a is formed in a cylindrical shape, for example, and is provided at one end in the arrangement direction (longitudinal direction of the manifold 22). The manifold 22 and the supply port 22a are connected by flow channels (not shown) provided through the upper portion of the fifth flow channel plate 52, the sixth flow channel plate 53, and the seventh flow channel plate 54, respectively. ing.

A plurality of individual channels 64 are connected to the manifold 22 respectively. The individual channel 64 has an upstream end connected to the manifold 22 and a downstream end connected to the base end of the nozzle 21 . The individual channel 64 is composed of the first communication hole 25, the supply throttle channel 26 which is an individual throttle channel, the second communication hole 27, the pressure chamber 28, and the descender 29, and these components are arranged in this order. be done.

The first communication hole 25 has its lower end connected to the upper end of the manifold 22, extends upward in the stacking direction from the manifold 22, and penetrates the upper portion of the fifth channel plate 52 in the stacking direction.

The upstream end of the supply throttle passage 26 is connected to the upper end of the first communication hole 25 . The supply throttle channel 26 is formed by, for example, half-etching, and is configured by a groove recessed from the lower surface of the sixth channel plate 53 . The second communication hole 27 is connected at its upstream end to the downstream end of the supply throttle path 26, extends upward in the stacking direction from the supply throttle path 26, and is formed to penetrate the sixth flow path plate 53 in the stacking direction. It is

The pressure chamber 28 has its upstream end connected to the downstream end of the second communication hole 27 . The pressure chambers 28 are formed through the seventh flow path plate 54 in the stacking direction.

The descender 29 includes a spacer plate 47, a first channel plate 48, a second channel plate 49, a third channel plate 50, a fourth channel plate 51, a fifth channel plate 52, and a sixth channel plate 53. in the stacking direction, and is arranged on the left side of the manifold 22 in the width direction in FIG. The descender 29 has its upstream end connected to the downstream end of the pressure chamber 28 and its downstream end connected to the base end of the nozzle 21 . The nozzle 21 overlaps the descender 29 in the stacking direction, for example, and is arranged in the center of the descender 29 in the direction (width direction) perpendicular to the stacking direction.

The vibration plate 55 is laminated on the seventh channel plate 54 and covers the upper end openings of the pressure chambers 28 .

Actuator 60 includes common electrode 61, piezoelectric layer 62 and individual electrodes 63, which are arranged in that order. The common electrode 61 covers the entire surface of the diaphragm 55 via the insulating film 56 . The piezoelectric layer 62 covers the entire surface of the common electrode 61 . The individual electrode 63 is provided for each pressure chamber 28 and arranged on the piezoelectric layer 62 . One actuator 60 is composed of one individual electrode 63, a common electrode 61, and a portion of the piezoelectric layer 62 sandwiched between the two electrodes.

The individual electrodes 63 are electrically connected to the driver IC. This driver IC receives a control signal from a control device 71 to be described later, generates a drive signal, and applies it to the individual electrode 63 . On the other hand, the common electrode 61 is always held at the ground potential. In such a configuration, the active portion of the piezoelectric layer 62 expands and contracts along with the two electrodes 61 and 63 in the plane direction according to the drive signal. Accordingly, the vibration plate 55 is cooperatively deformed, and the volume of the pressure chamber 28 is increased or decreased. As a result, an ejection pressure for ejecting ink droplets from the nozzles 21 is applied to the pressure chambers 28 .

In the ejection head 20 as described above, the supply port 22a is connected to the sub-tank 18 via a pipe. When a pressure pump provided in the pipe is driven, ink flows from the sub-tank 18 through the pipe and into the manifold 22 via the supply port 22a. Ink flows from the manifold 22 through the first communication hole 25 into the supply throttle passage 26 , and from the supply throttle passage 26 through the second communication hole 27 into the pressure chamber 28 . The ink then flows through the descender 29 and into the nozzle 21 . Here, when ejection pressure is applied to the pressure chamber 28 by the actuator 60, an ink droplet is ejected from the nozzle hole 21a.

FIG. 3 is a block diagram showing the configuration of the droplet discharge device 10 of FIG. FIG. 4 is a diagram showing how the ink droplets Id in flight ejected from the ejection head 20 are irradiated with the laser light Li, and FIG. 5 is an enlarged view of the region Ep in FIG. 6 is a plan view showing the arrangement of the light source 80 and the detection device 81. As shown in FIG.

As shown in FIG. 3, the droplet ejection device 10 includes, in addition to the components described above, a control device 71 composed of a CPU and the like, a RAM 72, a ROM 73, a head driver IC 74, a waveform generation circuit 76, a light source 80, and a detection device 81. , motor driver ICs 30 and 32 , a conveying motor 31 and a carriage motor 33 .

The light source 80 irradiates the flying ink droplets Id with light after they are ejected from the ejection head 20 until they land on the print medium W. As shown in FIG. In this embodiment, the light source 80 is, for example, a semiconductor laser, and irradiates the flying ink droplets Id with laser light Li. When the ink droplets Id are irradiated with the laser light Li, a phenomenon occurs in which the ink droplets Id act like a ball lens and the laser light Li is refracted.

The detection device 81 is configured to be movable in the optical axis direction Dl of the laser beam Li. The detection device 81 detects the refracted light Lk after the laser light Li emitted from the light source 80 has passed through the flying ink droplet Id. In this embodiment, the detection device 81 is, for example, a photodiode.

The control device 71 receives detection results from the detection device 81 . The control device 71 causes the light source 80 to irradiate the laser beam Li while the ejection head 20 continuously ejects the ink droplets Id. At this time, the control device 71 causes the detection device 81 to scan in the optical axis direction Dl. Then, the control device 71 calculates the volume of the ink droplet Id based on the light amount of the refracted light Lk detected by the detection device 81 when the detection device 81 is caused to scan. A method of calculating the volume of the ink droplet Id by the control device 71 will be described in detail later. A waveform generation circuit 76 generates an ejection waveform of a signal for driving the actuator 60 .

The RAM 72 stores information such as ejection data and the refractive index of the ink droplet Id. Further, the ROM 73 stores a droplet discharge program, a control program for performing various data processing, and the like.

The head driver IC 74 receives instructions from the control device 71 and causes the ejection head 20 to continuously eject ink droplets Id. The motor driver IC 30 receives instructions from the control device 71 and controls the driving of the conveying motor 31 . The transport motor 31 transports the print medium W in the transport direction by operating the transport rollers 15 . Further, the motor driver IC 32 receives instructions from the control device 71 and controls the driving of the carriage motor 33 . The carriage motor 33 moves the ejection head 20 in the main scanning direction by operating the carriage 16 .

Next, a method for calculating the volume of the ink droplet Id by the control device 71 will be described with reference to the drawings.

As shown in FIG. 4 , the light source 80 is arranged on one side with respect to the position of the ejection head 20 in the optical axis direction Dl of the laser light Li emitted from the light source 80 . The light source 80 is arranged in a box-shaped light source housing portion 82 . The light source housing portion 82 has a slit 82a on the side in the emission direction of the laser light Li emitted from the light source 80 . A lens 83 is arranged in the light source housing portion 82 so as to cover the slit 82 a from the inside of the light source housing portion 82 . In such a configuration, the laser light Li emitted from the light source 80 passes through the lens 83 and is then ejected from the ejection head 20 to irradiate the flying ink droplets Id.

As shown in FIG. 5, the detection device 81 is arranged on the other side with respect to the position of the ejection head 20 in the optical axis direction Dl of the laser beam Li. The detection device 81 is arranged at a predetermined distance from the light source 80 in the optical axis direction Dl. The initial position of the detection device 81 in the optical axis direction Dl is stored in advance in the RAM 72 or the like. The detection device 81 is configured to be able to scan along the optical axis direction Dl of the laser beam Li. The detection device 81 also has a slit 85 into which the refracted light Lk enters. The detection device 81 detects the refracted light Lk entering through the slit 85 .

The arrangement of the light source 80 and the detection device 81 described above with respect to the ejection head 20 is as follows. As shown in FIG. 6, the ejection head 20 has a plurality of nozzle rows NL arranged side by side in the main scanning direction. The plurality of nozzle rows NL includes, for example, a nozzle row NL for ejecting yellow ink droplets Id, a nozzle row NL for ejecting magenta ink droplets Id, a nozzle row NL for ejecting cyan ink droplets Id, and a nozzle row NL for ejecting black ink droplets. includes a nozzle row NL for ejecting ink droplets Id. A light source 80 and a detection device 81 are provided for each nozzle row NL.

Here, as described above, when the control device 71 causes the light source 80 to irradiate the laser light Li in a state in which the ejection head 20 continuously ejects the ink droplets Id, the detection device 81 is scanned in the optical axis direction Dl. Let At this time, the control device 71 calculates the volume of the ink droplet Id based on the light amount of the refracted light Lk detected by the detection device 81 when the detection device 81 is scanned. A detailed description will be given below.

The control device 71 calculates the focal length f of the refracted light Lk based on each specification information of the light source 80 and the detection device 81 and the maximum light quantity position _ZPDmax . Specifically, in FIG. 5, the control device 71 causes the light source 80 to scan the detection device 81, and the position (hereinafter referred to as the maximum light amount position) Z Get _PDmax . In this case, the control device 71 obtains the maximum light amount position _ZPDmax based on the initial position of the detection device 81 and the distance over which the detection device 81 is moved.

Next, the controller 71 calculates the focal position _Zf of the refracted light Lk. In this case, considering that the laser beam Li is a beam whose intensity distribution in the plane perpendicular to the optical axis direction Dl is close to Gaussian distribution, the focal position Z _f Calculate In Equation 1 below, ω(z) is the radius of the laser beam at an arbitrary coordinate z in the optical axis direction Dl and is equal to the slit diameter d of the slit 85 . ω ₀ is the laser radius at the focal position Z _f and is stored in the RAM 72 in advance. λ is the wavelength of the laser light Li, which is stored in the RAM 72 in advance. z is the distance from the focal position _Zf to the maximum light amount position _ZPDmax , and is _Zg in FIG. Also, ^M2 is a factor representing the quality of the laser beam.

From _Equation 1 above, the control device 71 calculates the focal position Z _f by focal position Z f =maximum light amount position Z _PDmax -distance Z _g .

Here, the focal length f can be calculated by Equation 2 below. In Equation 2 below, n is the refractive index of the ink droplet Id and r is the radius of the ink droplet Id. The refractive index n is stored in the RAM 72 in advance. The control device 71 calculates the radius r of the ink droplet Id using Equation 2 below. In this case, the control device 71 first calculates the focal length f from the calculated focal position _Zf and the coordinate _Zx . That is, the control device 71 calculates the focal length f from focal position Z _f -coordinate Z _x . Note that _Zx is the coordinate in the optical axis direction Dl of the x-th nozzle 21 that ejects the ink droplets Id irradiated with the laser beam Li in the nozzle row NL (FIG. 6), and the control device 71 acquires _Zx in advance. do. Based on the calculated focal length f and refractive index n, the control device 71 calculates the radius r of the flying ink droplet Id from Equation 2 below.

Subsequently, the control device 71 uses the calculated radius r of the ink droplet Id to calculate the volume V of the ink droplet Id from the calculation formula of V=(4/3)×π× ^r3 . The controller 71 compares the calculated volume V of the ink droplet Id with the volume of the ink droplet Id based on the ejection waveform (that is, the volume of the ink droplet Id to be ejected), and determines whether there is an ejection abnormality. discriminate. The control device 71 executes a correction process or the like as described later when there is an ejection abnormality, and causes the ejection head 20 to perform normal printing without performing the correction process or the like when there is no ejection abnormality.

7A to 7C are diagrams showing each ejection pulse in the ejection waveform before correction and each ejection pulse in the ejection waveform after correction.

The control device 71 determines whether or not there is an ejection abnormality according to the calculated volume of the ink droplet Id, and if there is an ejection abnormality, executes correction processing to change the ejection waveform. A specific description will be given below.

As shown in FIG. 7A, the ejection pulses P1, P2, and P3 before the correction process have the same voltage and different pulse widths. When an ejection abnormality is recognized, an ejection waveform is generated in which the number of pulses and the pulse width are varied, as shown in FIG. 7(a). Specifically, ejection pulses P4, P5, and P6 are added to the ejection waveform while ejection pulses P1, P2, and P3 remain. The voltages of the ejection pulses P4, P5 and P6 are the same as those of the ejection pulses P1, P2 and P3. Further, the pulse width of the ejection pulses P4, P5, P6 may be the same as the pulse width of any of the ejection pulses P1, P2, P3, or may be different from the pulse width of any of the ejection pulses P1, P2, P3. It may be a pulse width.

Alternatively, the ejection pulses P1, P2, and P3 before correction processing may be changed to ejection pulses P1a, P2a, and P3a shown in FIG. 7B by the correction processing. The voltage of the ejection pulse P1a is higher than the voltage of the ejection pulse P1, the voltage of the ejection pulse P2a is higher than the voltage of the ejection pulse P2, and the voltage of the ejection pulse P3a is higher than the voltage of the ejection pulse P3. The voltages of the ejection pulses P1a, P2a, and P3a increase in the order of the ejection pulse P1a, the ejection pulse P3a, and the ejection pulse P2a.

Alternatively, the ejection pulses P1, P2, and P3 before correction processing may be changed to ejection pulses P1a, P2a, and P3a shown in FIG. 7C by the correction processing, and ejection pulses P4a, P5a, and P6a may be added. good. The ejection pulse P4a has the same pulse width as the ejection pulse P4 in FIG. 7A, but has a lower voltage. The ejection pulse P5a has the same pulse width as the ejection pulse P5 in FIG. 7A, but has a higher voltage. The ejection pulse P6a has the same pulse width as the ejection pulse P6 in FIG. 7A, but has a higher voltage.

FIG. 8 is a flow chart showing processing after the volume of the ink droplet Id is calculated by the control device 71 . As shown in FIG. 8, the control device 71 calculates the volume V of the ink droplet Id by the method described above (step S1).

Subsequently, the controller 71 compares the calculated volume V of the ink droplet Id with the volume of the ink droplet Id based on the ejection waveform, and determines whether or not there is an ejection abnormality (step S2). If there is an ejection abnormality (YES in step S2), the control device 71 determines whether correction processing is possible (step S3). In this case, the control device 71 determines whether or not the ejection abnormality can be improved by the correction process described above, based on the comparison between the calculated volume of the ink droplet Id and the threshold value or the number of nozzles in which the ejection abnormality is recognized and the threshold value. do. For example, if the calculated volume of the ink droplet Id is too small compared to the threshold value, or if the number of nozzles in which ejection failure is recognized is too large compared to the threshold value, the controller 71 cannot improve the ejection failure. I judge.

If the correction process is possible (YES in step S3), the control device 71 executes the above-described correction process (step S4). On the other hand, if the correction process is not possible (NO in step S3), the control device 71 displays a message prompting replacement of the ejection head 20 (step S6). In this case, the control device 71 may turn on or blink a lamp or the like provided in the droplet ejection device 10, or may display on a touch panel display or the like of the printer in which the droplet ejection device 10 is provided.

On the other hand, if there is no ejection abnormality (NO in step S2), the control device 71 causes the ejection head 20 to perform normal printing without performing correction processing or the like (step S5).

As described above, according to the droplet ejection device 10 of the present embodiment, by moving the detection device 81 to calculate the focal position _Zf and by calculating the volume of the ink droplet Id, it is possible to determine whether the nozzle 21 has an ejection failure. It is possible to determine whether or not the actuator 60, which is a piezoelectric element, has deteriorated in the previous stage leading to . Accordingly, correction processing for adjusting the volume of the ink droplet Id can be executed based on the determination result. As a result, it is possible to prevent the ejection accuracy of each nozzle 21 from deteriorating, thereby obtaining desired image quality.

Further, in the present embodiment, V=(4/3)×π× The volume of the ink droplet Id is calculated by the calculation formula of ^r3 . As a result, the volume of the ink droplet Id can be accurately calculated, and therefore the ejection abnormality of the nozzle 21 can be accurately determined.

Further, in this embodiment, the ejection waveform is changed according to the calculated volume of the ink droplet Id. As a result, the ink droplets Id having a desired volume can be ejected from the nozzles 21 in which the ejection abnormality has occurred after the correction processing.

Furthermore, in this embodiment, by providing the light source 80 and the detection device 81 for each nozzle row NL, it is possible to sequentially calculate the droplet volume for each of the plurality of nozzles 21 in each nozzle row NL. As a result, the processing speed when calculating the droplet volume can be increased.

(Second embodiment)
In the first embodiment, the radius r of the ink droplet Id is calculated from Equation 2 based on the calculated focal length f and the refractive index n stored in advance in the RAM 72 . In contrast, in the second embodiment, the control device 71 acquires the radius r of the ink droplet Id from the ejection waveform. Then, using the focal length f calculated in the same manner as in the first embodiment and the acquired radius r of the ink droplet Id, the control device 71 calculates the distance of the ink droplet Id related to the currently used ink from Equation 2 above. Calculate the refractive index. The control device 71 determines whether the calculated refractive index and the pre-stored refractive index n are the same. Thus, if there is no identity, it can be determined that the currently used ink is not authorized.

According to this embodiment, the refractive index of the ink droplet Id can be accurately calculated from Equation 2 above from the focal length f of the refracted light Lk and the radius r of the ink droplet Id. This improves the accuracy of authenticity determination of the currently used ink.

(Modification)
The present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present invention. For example:

In the above embodiment, in the ejection waveform correction process performed when an ejection abnormality is recognized, the number of ejection pulses before correction is increased or decreased, and one of the ejection pulses after the increase or decrease is selected. pulse width was changed. Alternatively, only the voltage of the ejection pulse before correction is changed. Alternatively, the pulse number of the ejection pulse before correction is increased or decreased, and the pulse width and voltage of any one of the plurality of ejection pulses after being increased or decreased are changed. However, it is not limited to this. The content of the correction process is merely an example, and the combination of the number of ejection pulses, the voltage, and the pulse width to be changed before and after the correction process can be set as appropriate.

In the above-described embodiment, the nozzle row NL for ejecting yellow ink droplets Id, the nozzle row NL for ejecting magenta ink droplets Id, the nozzle row NL for ejecting cyan ink droplets Id, and the nozzle row NL for ejecting black ink droplets A light source 80 and a detection device 81 are provided for each nozzle row NL that ejects ink droplets Id. However, it is not limited to this. A light source 80 and a detection device 81 are provided for each nozzle row NL for an ejection head provided with a nozzle row NL for ejecting white ink droplets Id and a nozzle row NL for ejecting clear ink droplets Id. may

REFERENCE SIGNS LIST 10 droplet ejection device 20 ejection head 21 nozzle 60 actuator 71 control device 72 RAM
73 ROMs
80 light source 81 detection device Dl optical axis direction Id ink droplet Li laser light Lk refracted light NL nozzle row W print medium

Claims (7)

an ejection head that ejects droplets onto a print medium;
a light source that irradiates the droplets in flight with light after they are ejected from the ejection head and after they land on the printing medium;
a detection device configured to be movable in the optical axis direction of the light and detecting refracted light, which is light after the light emitted from the light source has passed through the droplet in flight;
a controller;
The control device is
irradiating the light from the light source and scanning the detection device in the optical axis direction in a state in which the liquid droplets are continuously ejected from the ejection head;
A droplet discharge device for calculating the volume of the droplet based on the light amount of the refracted light detected by the detection device when the detection device is scanned. Further comprising a storage unit for pre-storing information on the refractive index of the droplet,
The control device is
Acquiring a maximum light amount position, which is a position of the detection device at which the light amount of the refracted light becomes maximum when the detection device is scanned in the optical axis direction;
calculating the focal length of the refracted light based on each specification information of the light source and the detection device and the position of the maximum amount of light;
2. The droplet discharge device according to claim 1, wherein the volume of the droplet is calculated based on the focal length and the refractive index stored in the storage unit. The control device is
When the focal length is f and the refractive index is n, the radius r of the droplet obtained from the relational expression f={n/[2×(n−1)]}×r, and the liquid 3. The droplet ejection device according to claim 1, wherein the volume of the droplet is calculated by a formula of V=(4/3)*[pi]* ^r3 where V is the volume of the droplet. Further comprising a storage unit for pre-storing information on the refractive index of the droplet,
The control device is
Acquiring a maximum light amount position, which is a position of the detection device at which the light amount of the refracted light becomes maximum when the detection device is scanned in the optical axis direction;
calculating the focal length of the refracted light based on each specification information of the light source and the detection device and the position of the maximum amount of light;
obtain the radius of the droplet;
calculating the refractive index of the droplet based on the droplet radius and the focal length;
2. The liquid droplet ejecting apparatus according to claim 1, wherein identity between said calculated refractive index and said refractive index stored in said storage unit is determined. The controller controls the relationship f={n/[2×(n−1)]}×r, where f is the focal length, n is the refractive index, and r is the radius of the droplet. 5. The droplet discharge device according to claim 4, wherein the refractive index is calculated based on a formula. 6. The droplet ejection device according to claim 1, wherein said control device changes an ejection waveform according to the calculated volume of said droplet. The ejection head has a plurality of nozzle rows arranged side by side in the main scanning direction,
7. The droplet ejection device according to claim 1, wherein said light source and said detection device are provided for each nozzle row.

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