Printing device and printing method

Abstract

To provide a printing apparatus that has reduced ink discharge operation for increased printing efficiency.SOLUTION: A printing apparatus 1 includes a head 71 including a plurality of nozzles 76 configured to discharge liquid to a medium S, an abnormal nozzle detection unit 150 configured to detect an abnormal nozzle having a discharging defect among the plurality of nozzles 76, a contact detection unit 90 configured to detect contact between the head 71 and the medium S, a suction unit 95 configured to perform an ejection operation to eject the liquid from the plurality of nozzles 76, and a control unit 10. The control unit 10 executes a suction operation as an example of the ejection operation when the abnormal nozzle is detected and the contact between the head 71 and the medium S is detected, and the control unit 10 executes printing for complementing the abnormal nozzle when the abnormal nozzle is detected and the contact between the head 71 and the medium S is not detected.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a printing apparatus and a printing method. [Background technology]

[0002] Conventionally, printing devices that detect contact between a head that ejects liquid and a medium have been known. For example, Patent Document 1 discloses a printing device that controls printing operations according to the amount of displacement caused by contact between a displacement unit provided on a carriage that carries the head and the medium. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-122517 A Summary of the Invention [Problem to be solved by the invention]

[0004] The printing device described in Patent Document 1 stops printing operation and cleans the head depending on the degree of contact between the head and the medium. However, the causal relationship between contact between the head and the medium and nozzle clogging that requires cleaning is unclear. In other words, contact between the head and the medium does not necessarily result in clogging of the nozzle, and clogging of the nozzle does not necessarily require immediate cleaning. Therefore, the printing device of Patent Document 1 has a problem in that unnecessary cleaning is performed, resulting in reduced printing efficiency. [Means for solving the problem]

[0005] The printing device comprises a head having a plurality of nozzles that eject liquid onto a medium, an abnormal nozzle detection unit that detects an abnormal nozzle among the plurality of nozzles that has experienced an ejection failure, a contact detection unit that detects contact between the head and the medium, a discharge unit that performs a discharge operation to discharge the liquid from the plurality of nozzles, and a control unit, wherein the control unit performs the discharge operation when the abnormal nozzle is detected and contact between the head and the medium is detected, and performs printing to compensate for the abnormal nozzle when the abnormal nozzle is detected and contact between the head and the medium is not detected.

[0006] The printing method is a printing method for a printing device having a head having a plurality of nozzles that eject liquid onto a medium, an abnormal nozzle detection unit that detects an abnormal nozzle among the plurality of nozzles that has experienced an ejection failure, a contact detection unit that detects contact between the head and the medium, and a discharge unit that performs a discharge operation to discharge the liquid from the plurality of nozzles, and includes a step of detecting the abnormal nozzle, a step of detecting contact between the head and the medium, a step of performing the discharge operation when the abnormal nozzle is detected and contact between the head and the medium is detected, and a step of performing complementary printing to compensate for the abnormal nozzle when the abnormal nozzle is detected and contact between the head and the medium is not detected. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view showing a configuration of a printing apparatus according to an embodiment. [Diagram 2] FIG. 1 is a cross-sectional view showing a schematic configuration of a printing apparatus. [Diagram 3] FIG. 4 is a plan view illustrating the arrangement of a head and a contact detection unit. [Figure 4] FIG. 3 is a cross-sectional view showing the internal configuration of the head. [Diagram 5] FIG. 2 is a block diagram showing electrical connections of the printing device. [Figure 6] FIG. 4 is a block diagram showing the configuration of an abnormal nozzle detection unit. [Figure 7] FIG. 4 is a flowchart illustrating a printing method. [Figure 8A]FIG. 11 is a diagram showing an example of normal printing. [Figure 8B] FIG. 11 is a diagram showing an example of complementary printing. [Figure 9A] FIG. 11 is a diagram showing an example of normal printing. [Figure 9B] FIG. 11 is a diagram showing an example of complementary printing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] 1. Embodiment A schematic configuration of a printing device 1 according to an embodiment will be described. In the coordinate system shown in the drawings, both directions along the Z axis are up-down directions and the arrow direction is "up", both directions along the X axis are left-right directions and the arrow direction is "left", and both directions along the Y axis are front-rear directions and the arrow direction is "front". In addition, both directions along the X axis correspond to the main scanning direction, and the Y axis corresponds to the transport direction in the printing unit 70. The positional relationship along the transport direction of the medium S is also referred to as "upstream" and "downstream".

[0009] 1 and 2, the printing device 1 includes a supply unit 40, a transport unit 50, a guide unit 55, a winding unit 60, a printing unit 70, a suction unit 95, and a control unit 10 that controls each unit of the printing device 1. The supply unit 40 and the winding unit 60 are provided on a pair of legs 20 spaced apart in the X direction. The transport unit 50 and the guide unit 55 are supported by a base frame 21 that is mounted on the pair of legs 20. The printing unit 70 and the control unit 10 are provided inside a roughly rectangular parallelepiped housing 30 that is long in the X axis and supported by the base frame 21, located above the transport unit 50 and the guide unit 55.

[0010] The supply unit 40 is provided at the rear lower part of the housing 30. The supply unit 40 holds a roll R1 in which unused medium S is wound around a core tube 42. The supply unit 40 has a pair of holders 41 that sandwich both ends of the core tube 42. One of the holders 41 is equipped with a motor that supplies rotational force to the core tube 42. When the motor is driven to rotate the core tube 42, the medium S unwound from the roll R1 is fed to the printing unit 70. The supply unit 40 is interchangeably loaded with rolls R1 of medium S of different widths and numbers of turns.

[0011] The winding unit 60 is provided at the front lower part of the housing 30. In the winding unit 60, the medium S printed by the printing unit 70 is wound around a core tube 62 to form a roll body R2. The winding unit 60 includes a pair of holders 61 that sandwich both ends of the core tube 62. One of the holders 61 is provided with a motor that supplies rotational force to the core tube 62. The motor is driven to rotate the core tube 62, thereby winding the medium S around the core tube 62. The winding unit 60 may also include a tension roller that presses the back side of the medium S that hangs down due to its own weight, and applies tension to the medium S being wound around the core tube 62.

[0012] The guide unit 55 includes an upstream guide unit 56, a platen 57, and a downstream guide unit 58. The platen 57 has a plate shape long in the X-axis direction, and is provided at a position facing the printing unit 70. The platen 57 supports the medium S printed by the printing unit 70 from below. The upstream guide unit 56 is provided on the upstream side of the platen 57. A supply port 31 for supplying the medium S into the inside of the housing 30 is formed at a position above the upstream guide unit 56 on the rear surface of the housing 30. The upstream guide unit 56 guides the medium S supplied from the supply unit 40 to the platen 57 via the supply port 31. The downstream guide unit 58 is provided on the downstream side of the platen 57. A discharge port 32 for discharging the medium S to the outside of the housing 30 is formed at a position above the downstream guide unit 58 on the front surface of the housing 30. The downstream guide section 58 guides the medium S printed by the printing section 70 to the winding section 60 via the discharge opening 32.

[0013] The printing device 1 includes a first heater 86, a second heater 87, and a third heater 88 for heating the medium S. The first, second, and third heaters 86, 87, and 88 are, for example, tube heaters, and are attached to the lower surfaces of the upstream guide section 56, the platen 57, and the downstream guide section 58, respectively, via aluminum tape or the like. The first heater 86 is a heater for heating the upstream guide section 56, and gradually raises the temperature of the medium S supported by the upstream guide section 56 from room temperature to a target temperature. The second heater 87 is a heater for heating the platen 57, and keeps the medium S on the platen 57 facing the printing section 70 at a target temperature of 40°C. The third heater 88 is a heater for heating the downstream guide section 58, and heats the medium S supported by the downstream guide section 58 to 50°C, which is higher than the target temperature. As a result, the ink as a liquid ejected onto the medium S is quickly dried and fixed, and a high-quality image with little bleeding or blurring is formed.

[0014] The transport unit 50 includes a drive roller 51 that is disposed below the medium S and driven to rotate, a driven roller 52 that is disposed above the drive roller 51 and rotates following the rotation of the drive roller 51, and a motor that supplies rotational force to the drive roller 51. The drive roller 51 extends in a direction intersecting the transport direction of the medium S, and is provided between a platen 57 and an upstream guide unit 56. The driven roller 52 is configured to be movable so as to be separated from or pressed against the drive roller 51. When the motor is driven to drive the drive roller 51 to rotate, the medium S sandwiched between the driven roller 52 and the drive roller 51 is transported in the transport direction.

[0015] The printing unit 70 is disposed above the position of the platen 57. The printing unit 70 includes a head 71 that ejects ink onto the medium S on the platen 57, a carriage 72 on which the head 71 is mounted, and a head moving unit 75 that moves the carriage 72 in the main scanning direction. In addition, contact detection units 90 are provided on the upstream and downstream sides of the head 71 along the transport direction.

[0016] The head moving unit 75 moves the carriage 72 in the main scanning direction. The carriage 72 is supported by guide rails 73, 74 arranged along the X-axis, and is configured to be movable back and forth in the main scanning direction by the head moving unit 75. For example, a mechanism combining a ball screw and a ball nut, or a linear guide mechanism can be used as the mechanism for the head moving unit 75. Furthermore, the head moving unit 75 includes a motor that is a power source for moving the carriage 72 along the X-axis direction. When the motor is driven, the head 71 moves back and forth in the main scanning direction together with the carriage 72. Printing is performed by ejecting ink onto the medium S while the head 71 moves in the main scanning direction.

[0017] An operation unit 35 for performing setting operations and input operations is provided at the upper right part of the housing 30. A container mounting part 33 into which an ink containing container 34 capable of containing ink can be mounted is provided at the lower right part of the housing 30. A plurality of ink containing containers 34 are mounted in the container mounting part 33 corresponding to the type and color of ink. The ink containing container 34 and the head 71 are connected by a flexible tube, and ink is supplied to the head 71.

[0018] 3, the head 71 has a nozzle plate 77 in which a plurality of nozzles 76 are formed to eject various inks onto the medium S. For example, the head 71 includes a nozzle row K for ejecting black ink, a nozzle row C for ejecting cyan ink, a nozzle row M for ejecting magenta ink, a nozzle row Y for ejecting yellow ink, a nozzle row LK for ejecting gray ink, and a nozzle row LC for ejecting light cyan ink. Each of the nozzle rows K, C, M, Y, LK, and LC is made up of 400 nozzles 76 numbered #1 to #400.

[0019] The contact detection unit 90 is composed of multiple ultrasonic distance sensors 91. The distance sensor 91 has a transmitter 92 that transmits ultrasonic waves toward the medium S, and a receiver 93 that receives the ultrasonic waves reflected by the medium S. The distance sensor 91 determines the distance between the medium S and the distance sensor 91 based on the time from when the transmitter 92 emits ultrasonic waves to when the receiver 93 receives the ultrasonic waves. From this distance, it is possible to detect whether the medium S has come into contact with the head 71.

[0020] The suction unit 95 is an example of a discharge unit that performs a discharge operation to discharge liquid from the nozzle. The suction unit 95 is a device that performs a suction operation as an example of a discharge operation, which covers the head 71 and sucks ink from the head 71 through the nozzles 76. The suction unit 95 is provided on either one of the outer sides of the platen 57 in the X direction. The suction unit 95 is disposed at a position overlapping with the head 71 that reciprocates in the X direction in a plan view from the +Z direction. The suction unit 95 includes a negative pressure pump (not shown), and sucks ink from the head 71 by driving the negative pressure pump with the head 71 covered. This removes air bubbles, foreign matter, etc. that have entered the head 71, and allows the ejection of the nozzles 76 that have become clogged to be restored. Note that, in this embodiment, the suction operation of sucking the head 71 to suck ink has been exemplified as the discharge operation, but a pressurizing operation of pressurizing the ink supplied to the head 71 to forcibly discharge liquid from the nozzles 76 may be used. The suction unit 95 is also one of the cleaning means for cleaning the head 71. The cleaning means may be configured to include, in addition to the suction portion 95, a wiper that wipes the nozzle plate 77, a flushing box that receives ink that is forcibly discharged from the nozzles 76, and the like.

[0021] Next, the internal structure of the head 71 will be described. 4, the head 71 includes a piezoelectric element unit 170 that unitizes a plurality of piezoelectric elements 172, a fixed plate 173, a flexible cable 174, etc., a case 171 capable of housing the piezoelectric element unit 170, and a flow path unit 180 joined to the tip surface of the case 171. The piezoelectric elements 172 function as actuators that eject ink from each nozzle 76.

[0022] The case 171 is a block-shaped member made of synthetic resin and has a storage cavity 175 with both the front and rear ends open, and the piezoelectric element unit 170 is stored and fixed inside the storage cavity 175 .

[0023] The piezoelectric element 172 is formed in a comb-like shape that is elongated in the vertical direction. The piezoelectric element 172 is a laminated type piezoelectric vibrator formed by alternately laminating piezoelectric bodies and internal electrodes, and is a piezoelectric vibrator of a vertical vibration mode that can expand and contract in the vertical direction perpendicular to the lamination direction. The tip surface of each piezoelectric element 172 is joined to an island portion 176 of the flow path unit 180. The piezoelectric element 172 behaves in the same manner as a capacitor. That is, when the supply of a signal is stopped, the potential of the piezoelectric element 172 is held at the potential immediately before the supply of the signal is stopped.

[0024] The flow path unit 180 is constructed by stacking a nozzle plate 77 on one side of a flow path forming substrate 183 with a flow path forming substrate 183 in between, and an elastic plate 184 on the other side opposite the nozzle plate 77.

[0025] The nozzle plate 77 is made of a thin metal plate material on which a plurality of nozzles 76 are formed along the Y direction. The flow path forming substrate 183 is a plate-like member on which a series of ink flow paths consisting of a common ink chamber 186, an ink supply port 187, a pressure chamber 188, and a nozzle communication port 189 are formed. In this embodiment, this flow path forming substrate 183 is produced by etching a silicon wafer. The elastic plate 184 is a composite plate material with a double structure in which a resin film 181 is laminated on a stainless steel support plate 182, and an island portion 176 is formed by removing a ring-shaped portion of the support plate 182 corresponding to the pressure chamber 188.

[0026] In this head 71, a series of ink flow paths are formed for each nozzle 76, from the common ink chamber 186 through the pressure chamber 188 to the nozzle 76. The piezoelectric element 172 is deformed by charging and discharging it. That is, the piezoelectric element 172 in the longitudinal vibration mode contracts in the vibrator longitudinal direction when charged, and expands in the vibrator longitudinal direction when discharged. Therefore, when the potential is increased by charging, the island portion 176 is pulled toward the piezoelectric element 172, and the resin film 181 around the island portion 176 is deformed, causing the pressure chamber 188 to expand. When the potential is decreased by discharging, the pressure chamber 188 contracts.

[0027] In this way, since the volume of the pressure chamber 188 can be controlled according to the electric potential, it is possible to generate pressure fluctuations in the ink inside the pressure chamber 188, and to eject the ink from the nozzle 76. For example, by temporarily expanding the pressure chamber 188, which has a constant volume, and then suddenly contracting it, it is possible to eject the ink as droplets.

[0028] In this embodiment, the configuration using the longitudinal vibration type piezoelectric element 172 is illustrated, but the present invention is not limited to this. For example, a bending deformation type piezoelectric vibrator formed by laminating a lower electrode, a piezoelectric layer, and an upper electrode may be used.

[0029] Next, the electrical configuration of the printing device 1 will be described with reference to FIG.

[0030] The printing device 1 records an image or the like on a medium S based on image data input from an input device 2. The input device 2 is a device capable of saving and transmitting image data, such as a personal computer, a smartphone, or a tablet terminal.

[0031] The printing device 1 has a control unit 10 that controls each unit provided in the printing device 1. The control unit 10 includes an I / F (Interface) unit 11, a CPU (Central Processing Unit) 12, a storage unit 13, a control circuit 14, an abnormal nozzle detection unit 150, and the like. The I / F unit 11 is for transmitting and receiving data between the input device 2 and the control unit 10, and receives image data and the like transmitted from the input device 2. The CPU 12 is a processing unit that processes various input signals and generates print data for executing printing from received image data. The CPU 12 controls the entire printing device 1 based on the programs and print data stored in the storage unit 13. The storage unit 13 is a storage medium for securing an area for storing programs of the CPU 12, a working area, etc., and has memory elements such as a RAM (Random Access Memory) and an EEPROM (Electrically Erasable Programmable Read Only Memory). The storage unit 13 stores general image processing application software that handles image data, and printer driver software that generates print data for causing the printing device 1 to execute printing.

[0032] The control circuit 14 is a circuit that generates control signals for controlling the transport unit 50, the head moving unit 75, the suction unit 95, the head 71, etc., based on the print data and the calculation results of the CPU 12. The control circuit 14 includes a drive signal generating unit 14a, an ejection signal generating unit 14b, and a movement signal generating unit 14c. The drive signal generating unit 14a is a circuit that generates a drive control signal for driving the piezoelectric element 172 corresponding to each nozzle 76. By applying the generated drive control signal to the piezoelectric element 172, ink is ejected from the nozzle 76. The ejection signal generating unit 14b is a circuit that generates an ejection control signal for controlling the selection of the nozzles 76 that eject ink, the ejection timing of the ink, and the like, based on the print data and the calculation results of the CPU 12. The movement signal generating unit 14 c is a circuit that generates a movement control signal for driving the transport unit 50 and the head moving unit 75 based on the print data and the calculation results of the CPU 12 .

[0033] The control unit 10 performs a main scan in which the carriage 72 moves along the main scanning direction while ejecting ink from the nozzles 76 in response to a control signal output from the control circuit 14, thereby forming a raster line on the medium S in which dots are arranged along the X-axis. The control unit 10 also performs a sub-scan in which the medium S moves in the transport direction in response to a control signal output from the control circuit 14. By alternately performing these main and sub-scans, a desired image based on image data is printed on the medium S. In the following description, the main scan is also referred to as a "pass."

[0034] The control unit 10 controls the suction unit 95 to perform a suction operation in response to a control signal output from the control circuit 14. The control unit 10 also receives a signal output from the contact detection unit 90 and detects contact between the medium S and the head 71.

[0035] The abnormal nozzle detection unit 150 detects an abnormal nozzle among the multiple nozzles 76 that has become clogged and has an ejection defect. When a drive signal is input to the piezoelectric element 172 by the control unit 10, the piezoelectric element 172 vibrates and ink is ejected from the nozzle 76. After ejecting the ink, the piezoelectric element 172 generates residual vibration until the next drive signal is input. The frequency of the residual vibration of the piezoelectric element 172 corresponding to the nozzle 76 that has an ejection defect due to air bubbles entering the pressure chamber 188 changes. The abnormal nozzle detection unit 150 detects an abnormal nozzle that has an ejection defect based on the residual vibration of the piezoelectric element 172 corresponding to each nozzle 76.

[0036] 6, the abnormal nozzle detection unit 150 includes residual vibration detection means 151, measurement means 155, and judgment means 156. The residual vibration detection means 151 is composed of an oscillation circuit 152, an F / V conversion circuit 153, and a waveform shaping circuit 154. The measurement means 155 measures the frequency, amplitude, etc. from the residual vibration waveform data detected by the residual vibration detection means 151. The judgment means 156 judges whether the nozzle 76 is defective in ejection based on the frequency, etc. measured by the measurement means 155.

[0037] Residual vibration detection means 151 detects an oscillation frequency by forming a vibration waveform in F / V conversion circuit 153 and waveform shaping circuit 154 from the oscillation circuit 152 oscillating based on the residual vibration of piezoelectric element 172. Then, measurement means 155 measures the frequency of the residual vibration based on the detected vibration waveform, and determination means 156 detects ejection defects of nozzle 76 based on the measured frequency of the residual vibration, etc. In this embodiment, a printing device 1 is exemplified that is configured with an abnormal nozzle detection unit 150 that detects abnormal nozzles based on residual vibrations, but a method of detecting an abnormal nozzle that has experienced an ejection defect may also be a method of detecting ink ejected from the nozzle 76 with an optical sensor, or a method of reading and detecting dots of ink ejected onto the medium S with a scanner.

[0038] Next, the printing method of the printer 1 will be described with reference to FIG.

[0039] Step S101 is an abnormal nozzle detection step for detecting an abnormal nozzle. The abnormal nozzle detection unit 150 of the control unit 10 receives residual vibrations of the piezoelectric elements 172 corresponding to each nozzle 76, which are generated by a pass executed before the pass in which ink is ejected from the nozzle 76 that is currently executed.

[0040] Step S102 is a process for determining whether or not there is an abnormal nozzle. The abnormal nozzle detection unit 150 determines whether or not there is an abnormal nozzle that has caused an ejection defect based on the received residual vibration of the piezoelectric element 172. If there is an abnormal nozzle (Step S102: Yes), the process proceeds to Step S103. If there is no abnormal nozzle (Step S102: No), the process proceeds to the main scanning process of Step S108.

[0041] Step S103 is a medium contact detection step for detecting contact between the head 71 and the medium S. The control unit 10 receives an output signal output from the contact detection unit 90 in a pass executed before the currently executed pass in which ink is ejected from the nozzles 76.

[0042] Step S104 is a process for judging whether or not there has been contact between the head 71 and the medium S. The control unit 10 calculates the distance between the contact detection unit 90 and the medium S from the received output signal, and judges whether or not there has been contact between the head 71 and the medium S. For example, the control unit 10 judges that there has been contact between the head 71 and the medium S when a state in which the height of the medium S is 0.2 mm or more higher than the height of the head 71 continues for 10 msec or more. If there has been contact between the head 71 and the medium S (Step S104: Yes), the process proceeds to Step S105. If there has not been contact between the head 71 and the medium S (Step S104: No), the process proceeds to Step S106.

[0043] Step S105 is a suction step in which a suction operation is performed. If an abnormal nozzle is detected and contact between the head 71 and the medium S is detected, there is a high possibility that an air bubble larger than the diameter of the nozzle 76 has entered the nozzle communication port 189 from the nozzle 76. If this air bubble is left, the interface between the air bubble and the ink will dry and solidify. After solidification, the large air bubble cannot be discharged even if a suction operation is performed to suck ink from the nozzle 76, making it difficult to recover the ejection of the nozzle 76 that has become clogged. Therefore, the control unit 10 stops the printing operation and performs the suction operation, and then proceeds to the main scanning execution step of step S108 to resume the printing operation.

[0044] Step S106 is a judgment step for judging whether or not complementary printing to compensate for abnormal nozzles is possible. The control unit 10 judges that complementary printing is impossible if the number of abnormal nozzles detected is equal to or greater than a threshold. For example, the threshold for the number of abnormal nozzles is set to 20. If complementary printing is impossible (Step S106: No), proceed to Step S105. If complementary printing is possible (Step S106: Yes), proceed to Step S107.

[0045] An example of complementary printing will now be described with reference to Figures 8A to 9B. In the following description, it is assumed that the head 71 has a nozzle row K formed of eight nozzles 76 aligned along the Y direction. Note that in Figures 8B and 9B, abnormal nozzles that cannot eject ink are indicated with an x. Each figure also shows the relative position between the medium S and the head 71, an arrow indicating the movement direction of the head 71, and the positions of the dots DT formed on the medium S.

[0046] As shown in FIG. 8A, for example, the print data prints a ruled line formed by dots DT arranged in a line on the medium S by discharging ink from nozzles 76 #1 to #8 in a pass that moves the head 71 in the direction of the arrow. As shown in FIG. 8B, when nozzle 76 #4 is determined to be an abnormal nozzle, the control unit 10 executes complementary printing to increase the amount of ink discharged from nozzles 76 #3 and #5. In this case, nozzles 76 #3 and #5 are complementary nozzles that complement nozzle 76 #4, which is an abnormal nozzle. As a result, the gap between dots DT formed by nozzle 76 #3 and dots DT formed by nozzle 76 #5 becomes narrow, so that they can be visually recognized as one ruled line. In the case of print data for printing the ruled line shown in FIG. 8A, in addition to the above threshold, the control unit 10 also determines that complementary printing is impossible when abnormal nozzles are detected consecutively.

[0047] Also, as shown in FIG. 9A, for example, the print data ejects ink from the odd-numbered nozzles 76 in a first pass in which the head 71 is moved in the direction of the arrow indicated by "1", and after the medium S is transported in the transport direction by four dots, ejects ink from the even-numbered nozzles 76 in a second pass in which the head 71 is moved in the direction of the arrow indicated by "2", thereby printing a ruled line formed by dots DT arranged in a row on the medium S. Note that in FIG. 9A, the dots DT formed in the first pass are represented by circles indicated by "1", and the dots DT formed in the second pass are represented by circles indicated by "2". Also, black circles indicate dots DT formed in passes other than the first pass and the second pass. As shown in FIG. 9B, when the nozzle 76 #7 is determined to be an abnormal nozzle, the control unit 10 executes complementary printing in which the dots DT that should be formed by the nozzle 76 #7 in the first pass are formed by the nozzle 76 #3 in the second pass. In this case, the nozzle 76 #3 is a complementary nozzle that complements the nozzle 76 #7, which is an abnormal nozzle. 9A and 9B, for convenience of explanation, the head 71 is shown moving in the transport direction relative to the medium S, but in reality, the medium S moves in the transport direction relative to the head 71. In the case of print data for printing the ruled lines shown in Fig. 9A, in addition to the above thresholds, the control unit 10 also determines that complementary printing is impossible when nozzles 76 that are complementary to each other are simultaneously detected as abnormal nozzles.

[0048] Step S107 is a nozzle complementation step in which a nozzle complementation process is performed on the print data. If an abnormal nozzle is detected and no contact between the head 71 and the medium S is detected, it is highly likely that the nozzle is clogged due to air bubbles smaller than the diameter of the nozzle 76 that have been mixed into the ink. Even after solidification, small air bubbles can be discharged by a suction operation that is performed according to a predetermined schedule, and the ejection of the nozzle 76 that has caused the nozzle clog can be restored. Therefore, in order to continue the printing operation, the control unit 10 regenerates print data for performing printing to complement the abnormal nozzle. The control unit 10 generates a drive control signal and an ejection control signal for driving the complementary nozzle that complements the abnormal nozzle.

[0049] Step S108 is a main scanning execution step for executing a main scan. The control unit 10 executes the pass based on the print data and ends this flow. This flow chart is repeatedly executed for each pass among the multiple passes for forming an image. Also, steps S101 to S104 have been explained separately for convenience of explanation, but in reality, they are executed substantially simultaneously.

[0050] In this embodiment, a configuration is illustrated in which the contact detection unit 90 is provided upstream and downstream of the head 71 along the transport direction, but the contact detection unit may also be provided upstream and downstream of the head 71 moving along the main scanning direction. In addition, in this embodiment, a serial head type printing device 1 has been exemplified as the head 71, which is mounted on a reciprocating carriage 72 and ejects ink while moving in the width direction of the medium S, but the head may also be a line head type printing device in which the heads are arranged in a fixed manner and extend in the width direction of the medium S.

[0051] As described above, the printing device 1 and printing method according to this embodiment can provide the following advantages.

[0052] The printing device 1 is equipped with an abnormal nozzle detection unit 150 that detects abnormal nozzles that have experienced ejection problems, a contact detection unit 90 that detects contact between the head 71 and the medium S, and a suction unit 95 as a discharge unit that discharges ink from the multiple nozzles 76. An abnormal nozzle detected when contact between the head 71 and the medium S is detected is likely to have caused an ejection defect due to air bubbles larger than the diameter of the nozzle 76 being mixed into the nozzle 76 as a result of the nozzle 76 rubbing against the medium S. If a large air bubble solidifies, it becomes difficult to recover from the ejection defect, so it is necessary to immediately perform a suction operation, which is an example of an ejection operation, to eject the air bubbles before they solidify. On the other hand, an abnormal nozzle detected without detecting contact between the head 71 and the medium S is likely to have caused an ejection defect due to air bubbles smaller than the diameter of the nozzle 76 mixed in the ink. Even after solidification, small air bubbles can be recovered from the ejection defect by performing a suction operation. Therefore, when an abnormal nozzle is detected and contact between the head 71 and the medium S is not detected, the control unit 10 executes printing to compensate for the abnormal nozzle. This reduces the number of times that the suction operation is performed by interrupting the printing operation. Therefore, it is possible to provide a printing device 1 that improves printing efficiency.

[0053] The control unit 10 executes a suction operation when the number of abnormal nozzles detected is equal to or greater than a threshold. When the number of abnormal nozzles increases, the deterioration of image quality due to complementary printing becomes visible. Since the control unit 10 executes a suction operation when the number of abnormal nozzles is equal to or greater than a threshold, it is possible to improve printing efficiency while suppressing deterioration of image quality.

[0054] The head 71 has a piezoelectric element 172 as an actuator for ejecting ink. The abnormal nozzle detection unit 150 detects an abnormal nozzle based on the residual vibration of the piezoelectric element 172, and therefore can suitably detect an abnormal nozzle in an inkjet head 71 that uses the piezoelectric element 172.

[0055] Distance sensors 91 are provided on the upstream and downstream sides of the head 71 along the transport direction. This makes it possible to suitably detect contact of the head 71 with the floating of the medium S occurring on the upstream side and contact of the head 71 with the floating of the medium S occurring on the downstream side.

[0056] The printing method includes a step of detecting an abnormal nozzle that has caused an ejection failure, a step of detecting contact between the head 71 and the medium S, and a step of performing a suction operation as an example of an ejection operation to eject ink from the head 71. An abnormal nozzle detected when contact between the head 71 and the medium S is detected is likely to have caused an ejection defect due to air bubbles larger than the diameter of the nozzle 76 being mixed into the nozzle 76 as a result of the nozzle 76 rubbing against the medium S. If a large air bubble solidifies, it becomes difficult to recover from the ejection defect, so it is necessary to immediately perform a suction operation to remove the air bubbles before they solidify. On the other hand, an abnormal nozzle detected without detecting contact between the head 71 and the medium S is likely to have caused an ejection defect due to air bubbles smaller than the diameter of the nozzle 76 mixed into the ink. Even after solidification, small air bubbles can be recovered from the ejection defect by performing a suction operation. Therefore, the printing method of the printing device 1 has a step of performing printing to complement the abnormal nozzle when an abnormal nozzle is detected and contact between the head 71 and the medium S is not detected. This reduces the number of times that the suction operation is performed by interrupting the printing operation. Therefore, a printing method that improves the printing efficiency of the printing device 1 can be provided. [Explanation of symbols]

[0057] Reference Signs List 1: printing device, 10: control unit, 50: transport unit, 70: printing unit, 71: head, 90: contact detection unit, 91: distance sensor, 95: suction unit, 150: abnormal nozzle detection unit, 172: piezoelectric element, S: medium.

Claims

1. A head having a plurality of nozzles for ejecting liquid onto a medium; an abnormal nozzle detection unit that detects an abnormal nozzle that has caused a discharge defect among the plurality of nozzles; a contact detection unit that detects contact between the head and the medium; a discharge unit that performs a discharge operation of discharging the liquid from the plurality of nozzles; A control unit, The control unit is When the abnormal nozzle is detected and contact between the head and the medium is detected, the discharge operation is performed. When the abnormal nozzle is detected and contact between the head and the medium is not detected, printing is performed to compensate for the abnormal nozzle. A printing device comprising:

2. the control unit executes the discharge operation when the number of abnormal nozzles detected is equal to or greater than a threshold value; 2. The printing device according to claim 1, wherein:

3. the head has a piezoelectric element as an actuator for ejecting the liquid, the abnormal nozzle detection unit detects the abnormal nozzle based on residual vibration of the piezoelectric element that occurs after the liquid is ejected; 3. The printing device according to claim 1 or 2, wherein:

4. The contact detection unit is an ultrasonic distance sensor, the head is provided on the upstream side and downstream side of the head along the transport direction in which the medium is transported; The printing device according to any one of claims 1 to 3, characterized in that

5. A printing method for a printing device including a head having a plurality of nozzles that eject liquid onto a medium, an abnormal nozzle detection unit that detects an abnormal nozzle that has an ejection failure among the plurality of nozzles, a contact detection unit that detects contact between the head and the medium, and a discharge unit that performs a discharge operation to discharge the liquid from the plurality of nozzles, comprising: detecting the abnormal nozzle; detecting contact between the head and the medium; executing the discharge operation when the abnormal nozzle is detected and contact between the head and the medium is detected; and performing complementary printing to compensate for the abnormal nozzle when the abnormal nozzle is detected and contact between the head and the medium is not detected. A printing method comprising:

Images