Printing device

Abstract

To provide a printing device capable of suppressing consumption of ink.SOLUTION: A printing device comprises: a switching mechanism for performing switching between a liquid contact state in which a predetermined liquid surface is brought into contact with a nozzle surface in the case of ink non-discharge from the nozzle, and a non-liquid contact state in which the nozzle surface is separated from the liquid surface; a first cleaning part that performs first cleaning that is cleaning for improving a discharge function of the nozzle; and a control unit. The control unit executes processing of switching from the liquid contact state to the non-liquid contact state by the switching mechanism, processing of detecting a discharge failure of at least one nozzle on the nozzle surface after the state has been switched to the non-liquid contact, and processing of determining whether the first cleaning is necessary based on the result of the detection. The control unit, if it is determined that the first cleaning is necessary, causes the first cleaning part to perform the first cleaning, and if it is determined that the first cleaning is unnecessary, does not cause the first cleaning part to perform the first cleaning.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present disclosure relates to a printing apparatus.

Background Art

[0002] Conventionally, there is known a printing apparatus that performs a tube cleaning process by moving a cap to a nozzle formation surface sealing position and driving a suction pump (Patent Document 1). In this printing apparatus, as a tube cleaning process, an ink dissolving solution in a dissolving solution tank is caused to flow into the cap through an air communication tube and then discharged to a waste ink tank. Further, the same document discloses that a maintenance process is performed in which a negative pressure is generated in the cap by driving a suction pump, and ink in the nozzle is forcibly discharged into the cap.

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 order to avoid occurrence of ejection failure in the nozzles on the nozzle surface, a process may be performed in which the nozzle surface is brought into contact with a cleaning liquid to reduce thickening of the ink in the nozzles during non-ejection when ink ejection is not performed. After the nozzle surface is brought into contact with the cleaning liquid, a purge may be performed to forcibly discharge the cleaning liquid that has entered the nozzles as a maintenance process. However, in the method of forcibly discharging ink by a suction pump as in the above-described conventional printing apparatus, the amount of ink discharged from the nozzles increases, and ink consumption increases.

[0005] An object of the present disclosure is to provide a printing apparatus capable of suppressing ink consumption.

Means for Solving the Problems

[0006] The printing apparatus of the present disclosure includes a discharge head having a nozzle surface provided with a plurality of nozzles, a switching mechanism that switches between a liquid contact state in which a predetermined liquid surface is brought into contact with the nozzle surface and a non-liquid contact state in which the nozzle surface is separated from the liquid surface when ink is not discharged from the nozzles, a first cleaning unit that executes a first cleaning which is a cleaning for improving the discharge function of the nozzles, and a control device. The control device executes a process of switching from the liquid contact state to the non-liquid contact state by the switching mechanism, a process of detecting a discharge failure of at least one of the nozzles on the nozzle surface after switching to the non-liquid contact state, and a process of determining whether the first cleaning is necessary based on the result of the detection. When it is determined that the first cleaning is necessary, the first cleaning unit is made to execute the first cleaning, and when it is determined that the first cleaning is unnecessary, the first cleaning unit is not made to execute the first cleaning.

Advantages of the Invention

[0007] According to the present disclosure, when it is determined that the first cleaning is necessary based on the detection result of the discharge failure of the nozzles, the first cleaning is executed, and when it is determined that the first cleaning is unnecessary, the first cleaning is not executed. Thereby, the amount of ink discharged from the nozzles is reduced as compared with the case where the first cleaning is performed regardless of the presence or absence of a discharge failure of the nozzles after switching from the liquid contact state for suppressing thickening of the ink in the nozzles to the non-liquid contact state.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0009] Hereinafter, a printing apparatus according to an embodiment of the present disclosure will be described with reference to the drawings. The printing apparatus described below is merely one embodiment of the present disclosure. Therefore, the present disclosure is not limited to the following embodiments, and additions, deletions, and changes are possible without departing from the spirit of the present disclosure.

[0010] FIG. 1 is a plan view of a printing apparatus 100 according to an embodiment. FIG. 2 is a block diagram showing the configuration of the printing apparatus 100 of FIG. 1. In FIG. 1 and each of the following figures, directions orthogonal to each other are defined as a first direction Dx, a second direction Dy, and a third direction Dz. The first direction Dx is, for example, the left-right direction (main scanning direction), the second direction Dy is, for example, the front-rear direction, and the third direction Dz is, for example, the up-down direction. One direction of the first direction Dx is defined as Dx1, and the direction opposite to Dx1 is defined as Dx2. One direction of the second direction Dy is defined as a conveyance direction Dy1, and the direction opposite to Dy1 is defined as Dy2. One direction of the third direction Dz is defined as Dz1, and the direction opposite to Dz1 is defined as Dz2. However, the above directions are all examples and are not limiting.

[0011] The printing apparatus 100 in FIG. 1 performs printing by ejecting ink droplets of ink onto a printing medium W such as printing paper and fabric. The printing apparatus 100 prints a color image by ejecting ink droplets of each color of yellow (Y), magenta (M), cyan (C), and black (K), which are collectively referred to as color ink, onto the printing medium W. Further, when a color image is printed on, for example, fabric as the printing medium W, in order to reduce the influence on the color and material of the fabric, ink droplets of white ink (W) are ejected first as undercoat ink, and the ink droplets of the color ink are ejected onto the ink droplets.

[0012] As shown in FIG. 1, the printing apparatus 1 includes a storage tank 57, a discharge head 55, a carriage 54, and a pair of guide rails 69. The carriage 54 supports the discharge head 55. The carriage 54 is supported by a pair of guide rails 69 extending in the first direction Dx, and reciprocates in the first direction Dx along the guide rails 69. As a result, the discharge head 55 reciprocates in the first direction Dx. Further, the discharge head 55 is connected to the storage tank 57 via a tube 57a. In the printing process, the control device 20 forms dots along the first direction Dx by ejecting ink droplets from the discharge head 55 onto the printing medium W while moving the discharge head 55 in the direction Dx1 or the direction Dx2 by the carriage 54. Then, the control device 20 conveys the printing medium W by a predetermined distance in the conveyance direction Dy1 by a platen (not shown) after the dots are formed. By repeating the dot formation and the conveyance operation, a predetermined image is formed on the printing medium W.

[0013] The ejection head 55 has, for example, a plurality of nozzles 55a that eject ink droplets of respective colors of color ink onto a printing medium W. The plurality of nozzles 55a are provided on a nozzle surface 55b of the ejection head 55 described later. The plurality of nozzles 55a form nozzle rows NR for each color along the second direction Dy. By ejecting ink droplets of four colors onto the printing medium W, a color image is printed on the printing medium W. Although not shown in FIG. 1, an ejection head (hereinafter referred to as a white ejection head) that ejects white (W) ink droplets may be provided on the carriage 54. In this case, the ejection head 55 and the white ejection head may be arranged spaced apart from each other in the second direction Dy in one carriage 54. Alternatively, the ejection head 55 and the white ejection head may be arranged spaced apart from each other in the first direction Dx in one carriage 54. Further, a carriage that supports the white ejection head may be provided separately from the carriage 54 that supports the ejection head 55. Due to such positional relationships of the plurality of ejection heads, the number and positions of the cap 51 and the cap portion 91 described later may change.

[0014] Ink is stored in the storage tank 57. The storage tank 57 is provided for each type of ink. For example, five storage tanks 62 are provided, and each storage tank 62 stores any one of cyan, magenta, yellow, black, and white ink.

[0015] The printing apparatus 1 further includes a wiping unit 41, a pump 52, a switching mechanism 59 described later, a receiving unit 58, and a cap unit 91.

[0016] The wiping unit 41 is disposed between a pair of guide rails 69 on one side in the first direction Dx so as to overlap the movement region of the carriage 54. The wiping unit 41 has wipers 43, 44 and a movement mechanism 42. The movement mechanism 42 is composed of, for example, a motor, a ball screw, or a rack and pinion, etc., and supports the wipers 43, 44. With the nozzle surface 55b disposed at a position facing these wipers 43, 44, for example, the movement mechanism 42 moves in the second direction Dy or the first direction Dx, or the carriage 54 moves in the first direction Dx. Thereby, the wipers 43, 44 wipe the nozzle surface 55b, and the nozzle surface 55b is cleaned. The position of the discharge head 55 when the nozzle surface 55b is disposed to face the wipers 43, 44 is defined as the wipe position WP. Note that the wiping by the wiping unit 41 is included in the first cleaning and the second cleaning described later.

[0017] The switching mechanism 59 has a cap 51 and a lifting mechanism 53 described later. The cap 51 is disposed between a pair of guide rails 69 so as to overlap the movement region of the carriage 54. The lifting mechanism 53 is composed of, for example, a motor, a ball screw, or a rack and pinion, etc., and is connected to the cap 51. When the lifting mechanism 53 is driven, the cap 51 reciprocates in the third direction Dz. The details of the switching mechanism 59 will be described later.

[0018] The pump 52 supplies a liquid (for example, a cleaning liquid) into the cap 51 when the liquid contact treatment described later is performed. Further, the pump 52 generates a negative pressure in the cap 51 when performing the purge described later, thereby sucking the air in the cap 51, the ink in the nozzle 55a, and the cleaning liquid.

[0019] The cap portion 91 is disposed between a pair of guide rails 69 so as to overlap the moving region of the carriage 54. The cap portion 91 receives the ink droplets ejected from the nozzles 55a in a state where the nozzle surface 55b of the ejection head 55 faces the cap portion 91. The position of the ejection head 55 when the nozzle surface 55b faces the cap portion 91 is defined as the detection position DP. When the ejection head 55 is disposed at the detection position DP, ejection failure of the nozzles 55a is detected based on the presence or absence of ejection of ink droplets. Note that the detection process for ejection failure will be described in detail later. In the present embodiment, although the cap portion 91 is provided separately from the cap 51, the present invention is not limited to this. If the detection process for ejection failure, which will be described in detail later, is executed using the cap 51 at the standby position HP described later, the cap portion 91 may not be provided. In this case, a detection electrode 92 described later is disposed in the cap 51.

[0020] The receiving portion 58 is disposed between a pair of guide rails 69 on the other side in the first direction Dx so as to overlap the moving region of the carriage 54. The receiving portion 58 receives the ink droplets ejected from the nozzles 55a during non-printing in a state where the nozzle surface 55b of the ejection head 55 faces the receiving portion 58. The position of the ejection head 55 when the nozzle surface 55b faces the receiving portion 58 is defined as the flushing position FP. The process of ejecting ink droplets from the nozzles 55a at the flushing position FP is referred to as flushing. Note that flushing is included in the first cleaning and the second cleaning described later.

[0021] Subsequently, as shown in FIG. 2, the printing apparatus 100 includes an operation key 28, a display unit 29, a controller unit 6, motor driver ICs 30 and 31, a head driver IC 32, a pump driver IC 33, a wipe driver IC 34, a solenoid valve driver IC 35, a switching driver IC 36, a determination circuit 37, and a high voltage power supply circuit 40. The printing apparatus 100 further includes a conveyance motor 38, a carriage motor 39, and solenoid valves 78, 79, and 80.

[0022] The operation key 28 receives operation inputs from the user. The display unit 29 is constituted by, for example, a touch panel and displays predetermined information. A part of the display unit 29 may function as an operation key.

[0023] The controller unit 6 realizes a printing function based on an input from the operation key 28 or an external input and controls the display on the display unit 29. The controller unit 6 includes a control device 20 composed of a CPU, a ROM 21, a RAM 22, an EEPROM 23, an HDD 24, and an ASIC 25. The control device 20 is electrically connected to the ROM 21, the RAM 22, the EEPROM 23, the HDD 24, and the ASIC 25, and controls each driver ICs 30 to 36, the determination circuit 37, and the high-voltage power supply circuit 40.

[0024] The control device 20 executes various functions by executing a printing program stored in the ROM 21. The control device 20 may be implemented as one processor in the controller unit 6, or may be implemented as a plurality of processors cooperating with each other. The printing program may be read from a recording medium such as a computer-readable magneto-optical disk or a USB flash memory by a reading device and stored in the ROM 21.

[0025] The RAM 22 stores image data received from the outside and calculation results of the control device 20 and the like. The EEPROM 23 stores various initial setting information input by the user, the cumulative value of the number of printed sheets, and the like. The HDD 24 stores various data and the like.

[0026] The ASIC 25 has the driver ICs 30 to 36, the determination circuit 37, and the high-voltage power supply circuit 40 connected thereto. The control device 20 outputs various commands including a printing command based on the printing program to the ASIC 25. The ASIC 25 drives the driver ICs 30 to 36, the determination circuit 37, and the high-voltage power supply circuit 40 based on the various commands. Note that a mode in which the operation key 28, the display unit 29, and the driver ICs 30, 31, 33 to 36 are directly connected to the control device 20 may be adopted. Note that the determination circuit 37 and the high-voltage power supply circuit 40 will be described in detail later.

[0027] The conveyance motor 38 is connected to a platen (not shown) that supports the printing medium W. By driving the conveyance motor 38 with the motor driver IC 30, the platen reciprocates in the second direction Dy. As the platen reciprocates in the second direction Dy, the printing medium W placed on the platen is conveyed in the second direction Dy (i.e., the conveyance directions Dy1 and Dy2). Further, the carriage motor 39 is connected to the carriage 54. By driving the carriage motor 39 with the motor driver IC 31, the carriage 54 reciprocates in the first direction Dx. As a result, the ejection head 55 reciprocates in the first direction Dx. Further, the head driver IC 32 applies ejection pressure to a pressure chamber (not shown) by an actuator 56 provided in the ejection head 55. Thereby, ink droplets are ejected from the nozzles 55a. Note that the actuator 56 is included in a first cleaning unit CL1 that executes a first cleaning described later and a second cleaning unit CL2 that executes a second cleaning described later.

[0028] The suction operation of the pump 52 is controlled by the pump driver IC 33. The movement operation of the movement mechanism 42 of the wiper unit 41 is controlled by the wiper driver IC 34. Further, the opening and closing operations of the electromagnetic valves 78, 79, and 80 are controlled by the solenoid valve driver IC 35. Furthermore, the raising and lowering operation of the raising and lowering mechanism 53 of the switching mechanism 59 is controlled by the switching driver IC 36. Note that the pump 52 and the switching mechanism 59 are included in a first cleaning unit CL1 that executes a first cleaning described later, and the wiper unit 41 is included in a first cleaning unit CL1 that executes a first cleaning described later and a second cleaning unit CL2 that executes a second cleaning described later.

[0029] FIG. 3 is a diagram showing a configuration for forming a liquid contact state and a cap state. As shown in FIG. 3, the printing apparatus 100 includes a supply / discharge unit 70. The supply / discharge unit 70 includes a cleaning liquid tank 71, a supply channel 72, a discharge channel 73, a drain tank 74, an air release port 77, the pump 52 described above, and the electromagnetic valves 78, 79, and 80 described above.

[0030] The cleaning liquid tank 71 stores a cleaning liquid for cleaning the nozzle surface 55b. The supply flow path 72 connects the cleaning liquid tank 71 and the supply hole 75 provided in the cap 51, and supplies the cleaning liquid into the cap 51. The atmosphere release port 77, the solenoid valve 78, and the solenoid valve 79 are provided in the supply flow path 72. The solenoid valve 78 opens and closes the atmosphere release port 77. The solenoid valve 79 opens and closes the supply flow path 72.

[0031] The discharge flow path 73 connects the discharge hole 76 provided in the cap 51 and the drain tank 74, and discharges the ink and the cleaning liquid in the cap 51 to the drain tank 74. The solenoid valve 80 and the pump 52 are provided in the discharge flow path 73. The solenoid valve 80 opens and closes the discharge flow path 73. The pump 52 sucks air in the cap 51 and the like, the ink and the cleaning liquid forcibly discharged from the nozzle 55a during the execution of purging, and discharges them to the drain tank 74.

[0032] Here, in the printing apparatus 100, for the purpose of suppressing the thickening of the ink in the nozzle 55a, etc., for example, a process of bringing the liquid level of the cleaning liquid into contact with the nozzle surface 55b at regular intervals (hereinafter referred to as the liquid contact process) is performed. Hereinafter, the liquid contact process will be described. FIG. 4A is a diagram showing the liquid contact state and the coating state, and FIG. 4B is a diagram showing the non-liquid contact state and the non-coating state.

[0033] The switching mechanism 59 is moved to the position of the discharge head 55 (hereinafter referred to as the standby position HP) when the ink droplets are not discharged from the nozzle 55a (during non-printing) and the nozzle surface 55b faces the cap 51, and then switches between the liquid contact state and the non-liquid contact state. In this case, the lifting mechanism 53 of the switching mechanism 59 is driven to move the cap 51 in the third direction Dz, thereby forming a liquid contact state or a non-liquid contact state. The liquid contact state is a state in which a predetermined liquid level is in contact with the nozzle surface 55b, and the non-liquid contact state is a state in which the nozzle surface 55b is not in contact with the liquid level.

[0034] When liquid contact treatment is performed, the discharge head 55 is moved to the standby position HP. When the discharge head 55 moves to the standby position HP, as shown in FIG. 4B, the nozzle surface 55b of the discharge head 55 faces a cap 51 disposed at a position spaced apart in the third direction Dz (hereinafter referred to as the uncapping position) Pa. Thereafter, as shown in FIG. 4A, the cap 51 is moved from the uncapping position Pa to the cap position Pc by the elevating mechanism 53. Thereby, the nozzle surface 55b is covered by the cap 51.

[0035] Then, the solenoid valve 78 is closed, the solenoid valves 79 and 80 are opened, and the pump 52 is driven. As a result, the cleaning liquid in the cleaning liquid tank 71 is filled into the cap 51 located at the cap position Pc through the supply flow path 72. Thereby, a liquid contact state in which the nozzle surface 55b contacts the liquid level of the cleaning liquid is formed. The liquid contact treatment is thus executed. In order to maintain the state in which the nozzle surface 55b is in contact with the liquid level of the cleaning liquid, after a predetermined time has elapsed since the solenoid valve 78 was closed, the solenoid valves 79 and 80 were opened, and the pump 52 was driven, the solenoid valve 80 is closed and the operation of the pump 52 is stopped.

[0036] After the liquid contact treatment is executed for a certain period of time, the drainage treatment of the cleaning liquid is performed. In the drainage treatment, the solenoid valves 78 and 79 are opened and the atmosphere release port 77 is opened, so that the inside of the cap 51 is in a state of being in communication with the atmosphere. Then, the solenoid valve 80 is opened and the pump 52 is driven. As a result, the cleaning liquid in the cap 51 is discharged to the drainage tank 74 through the discharge hole 76 and the discharge flow path 73. After the drainage treatment is completed, the cap 51 is moved from the cap position Pc to the uncapping position Pa by the elevating mechanism 53. Thereby, a non-liquid contact state in which the nozzle surface 55b is not in contact with the liquid level of the cleaning liquid is formed.

[0037] Further, when the switching mechanism 59 performs a process (purging) of forcibly discharging ink from the nozzle 55a by the suction operation of the pump 52 during a non-discharge time (non-printing time) when ink droplets are not discharged from the nozzle 55a, the cap 51 is moved in the third direction Dz. Note that purging is included in the first cleaning described later.

[0038] When purging is executed, the switching mechanism 59 switches between a covering state and a non-covering state after the discharge head 55 is moved to the standby position HP. In this case, the lifting mechanism 53 of the switching mechanism 59 is driven to move the cap 51 in the third direction Dz, thereby forming a covering state or a non-covering state. The covering state is a state in which the nozzle surface 55b is covered by the cap 51 when purging is executed, and the non-covering state is a state in which the nozzle surface 55b and the cap 51 are separated. As an example, in FIG. 4A, the position of the cap 51 when the covering state is formed is the same as the position of the cap 51 when the liquid contact state is formed, and in FIG. 4B, the position of the cap 51 when the non-covering state is formed is the same as the position of the cap 51 when the non-liquid contact state is formed.

[0039] When the discharge head 55 moves to the standby position HP when purging is executed, as shown in FIG. 4B, the nozzle surface 55b of the discharge head 55 faces the cap 51 disposed at the uncapping position Pa. Thereafter, as shown in FIG. 4A, the cap 51 is moved from the uncapping position Pa to the cap position Pc by the lifting mechanism 53. Thereby, a covering state in which the nozzle surface 55b is covered by the cap 51 is formed.

[0040] Then, with the electromagnetic valves 78 and 79 opened and the atmosphere release port 77 opened, the inside of the cap 51 is brought into an atmosphere communication state. Then, the electromagnetic valve 80 is opened and the pump 52 is driven. As a result, the ink from the nozzle 55a is discharged into the cap 51. In this way, the purge is executed. The ink discharged into the cap 51 is discharged into the drain tank 74 through the discharge hole 76 and the discharge flow path 73. After the purge is completed, the cap 51 is moved from the cap position Pc to the uncapping position Pa by the elevating mechanism 53. As a result, a non-covered state in which the nozzle surface 55b and the cap 51 are separated is formed.

[0041] Next, the first cleaning executed by the first cleaning unit CL1 and the second cleaning executed by the second cleaning unit CL2 will be described.

[0042] The first cleaning unit CL1 is composed of an actuator 56 that executes flushing, a pump 52 and a switching mechanism 59 that execute purge, and a wiping unit 41 that executes wiping. The second cleaning unit CL2 is composed of the actuator 56 and the wiping unit 41.

[0043] The first cleaning executed by the first cleaning unit CL1 is a cleaning that improves the discharge function of the nozzle 55a. The second cleaning executed by the second cleaning unit CL2 is a cleaning that improves the discharge function of the nozzle 55a. The first cleaning includes a plurality of types of first cleaning. For example, the first cleaning includes the above-described purge, flushing, and wiping. The purge as the first cleaning is executed in a non-contact liquid state and a covered state after being switched from the non-covered state to the covered state by the switching mechanism 59.

[0044] The second cleaning includes a plurality of types of second cleaning. For example, the second cleaning includes the flushing and wiping described above. That is, the first cleaning includes a cleaning with a stronger improving power of the ejection function of the nozzle 55a than the second cleaning, and also includes a cleaning of the same type as the second cleaning. The second cleaning is executed by the second cleaning unit CL2 after being switched from the liquid contact state to the non-liquid contact state by the switching mechanism 59 and before performing the ejection failure detection process to be described in detail later.

[0045] The first cleaning includes a cleaning with a stronger improving power of the ejection function of the nozzle 55a than the second cleaning. Specifically, the first cleaning includes purging as a cleaning with a stronger improving power of the ejection function of the nozzle 55a than the second cleaning.

[0046] The strength or weakness of the above improving power can be defined by the ink consumption. For example, a cleaning with a strong improving power is a cleaning with a large ink consumption, and a cleaning with a weak improving power is a cleaning with a small ink consumption. Specifically, since wiping only wipes the nozzle surface 55b, the ink consumption is basically zero, but the reliability of discharging the ink in the nozzle 55a is relatively low. Therefore, it can be said that wiping is a cleaning with a weak improving power. Also, flushing vibrates the nozzle 55a for each nozzle 55a to discharge the ink in the nozzle 55a. For this reason, the amount of ink that can be discharged is less than that of purging, and thus the ink consumption is reduced, but the discharging accuracy of the ink in the nozzle 55a is not higher than that of purging. Therefore, it can be said that flushing is a cleaning with an intermediate level of improving power. Furthermore, purging performs a suction process on all the nozzles 55a by negative pressure. For this reason, the ink in the nozzle 55a is easily discharged, the amount of ink that can be discharged is more than that of flushing, and thus the ink consumption is increased, but the discharging accuracy of the ink is higher than that of flushing. Therefore, it can be said that purging is a cleaning with a strong improving power.

[0047] Next, the criteria for determining the necessity of performing the first cleaning will be described. FIG. 5 is a diagram showing a configuration for performing a discharge defect detection process. FIG. 6A is a diagram showing a change in the voltage value of the detection electrode 92 when ink is discharged from the nozzle 55a, and FIG. 6B is a diagram showing a change in the voltage value of the detection electrode 92 when ink is not discharged from the nozzle 55a.

[0048] As shown in FIG. 5, for example, a plate-shaped detection electrode 92 is disposed in the above-described cap portion 91. The detection electrode 92 is connected to a high-voltage power supply circuit 40 via a resistor 93. When the discharge defect detection process is executed, a predetermined positive potential (for example, about 600 V) is applied to the detection electrode 92 by the high-voltage power supply circuit 40. On the other hand, the discharge head 55 is held at the ground potential. Thereby, a predetermined potential difference is generated between the discharge head 55 and the detection electrode 92. A determination circuit 37 is connected to the detection electrode 92. The determination circuit 37 compares the potential of the signal output from the detection electrode 92 with the threshold value Vt and outputs a signal according to the result.

[0049] Specifically, after being switched from the liquid contact state to the non-liquid contact state by the switching mechanism 59, the discharge head 55 is disposed at the detection position DP by the carriage 54. In this state, ink is discharged from each nozzle 55a toward the detection electrode 92 from the nozzle 55a. Since there is a potential difference between the discharge head 55 and the detection electrode 92 as described above, the ink discharged from the nozzle 55a is charged. In this case, as shown in FIG. 6A, until the charged ink approaches the detection electrode 92 and lands on the detection electrode 92, the potential of the detection electrode 92 decreases from the potential Va when the discharge head 55 is not driven and reaches a potential Vb lower than the potential Va. Then, after the charged ink lands on the detection electrode 92, the potential of the detection electrode 92 gradually rises and returns to the potential Va. That is, the potential of the detection electrode 92 changes during the driving period Td of the discharge head 55. The threshold value Vt is set so that Va < Vt < Vb.

[0050] On the other hand, when no ink is ejected from the nozzle 55a, as shown in FIG. 6B, during the driving period Td of the ejection head 55, the potential of the detection electrode 92 hardly changes from the potential Va. In the above description, a positive potential is applied to the detection electrode 92 by the high-voltage power supply circuit 40. However, a negative potential (for example, about -600 V) may be applied to the detection electrode 92. In this case, conversely to the above, when ink is ejected from the nozzle 55a toward the detection electrode 92, until the charged ink approaches the detection electrode 92 and lands on the detection electrode 92, the potential of the detection electrode 92 rises from the potential Va. After the ink lands on the detection electrode 92, the potential of the detection electrode 92 gradually decreases and returns to the potential Va.

[0051] The determination circuit 37 compares the potential of the voltage signal output from the detection electrode 92 with the threshold value Vt during the driving period Td of the ejection head 55, and outputs a determination signal corresponding to the comparison result to the control device 20. The control device 20 detects ejection failure of at least one nozzle 55a on the nozzle surface 55b for each nozzle 55a based on the determination signal. The control device 20 counts the number of nozzles 55a with ejection failure as a result of the detection process. Note that in a configuration in which laser light is irradiated onto ink droplets before they are ejected from the nozzle 55a and reach the cap 51 (or the cap portion 91), and the light reception intensity (transmittance) of the laser light after the irradiation is detected, a detection process for ejection failure may be executed based on the detection result.

[0052] The control device 20 determines whether or not to execute the first cleaning based on the detection result. In this case, for example, the control device 20 determines whether or not to execute the first cleaning according to the number of nozzles 55a in which ejection defects have occurred, which was counted as described above. At this time, the control device 20 compares the number of nozzles 55a related to the ejection defect with a predetermined first threshold value. When the number of nozzles 55a related to the ejection defect is equal to or greater than the first threshold value, the control device 20 determines that the first cleaning is necessary. Further, when the number of nozzles 55a related to the ejection defect is less than the first threshold value, the control device 20 determines that the first cleaning is unnecessary. When the control device 20 determines that the first cleaning is necessary, it causes the first cleaning unit CL1 to execute the first cleaning. On the other hand, when the control device 20 determines that the first cleaning is unnecessary, it does not cause the first cleaning unit CL1 to execute the first cleaning.

[0053] The first cleaning includes purging, flushing, and wiping as a plurality of types of first cleaning as described above. The control device 20 determines the first cleaning to be executed among the plurality of types of first cleaning according to the result of the detection of the ejection defect, and causes the first cleaning unit CL1 to execute it.

[0054] The control device 20 determines the first cleaning to be executed among a plurality of types of first cleanings according to, for example, the positional distribution of the nozzles 55a where the ejection failure has occurred as a result of the ejection failure detection process. For example, in the ejection failure detection process, the positions of the respective nozzles 55a at the position of the nozzle surface 55b are stored in advance, and the control device 20 recognizes the positions of the nozzles 55a where the ejection failure has occurred. At this time, for example, a mode in which a predetermined number or more of nozzles 55a with ejection failures gather adjacent to each other is acquired by the control device 20 as the above positional distribution. In this case, for example, the control device 20 compares the size of the range related to the positional distribution (for example, the area of the region surrounded by a line connecting the outermost nozzles 55a when the nozzles 55a with ejection failures gather adjacent to each other) with a predetermined second threshold value. When the size is equal to or greater than the second threshold value, the control device 20 can determine a purge with strong improvement power as the first cleaning to be executed. Alternatively, the control device 20 may compare the length of the line segment connecting the nozzles 55a with the second threshold value when the nozzles 55a with ejection failures gather adjacent to each other instead of the above area. At this time, the line segment may be defined by the outermost nozzles 55a among the nozzles 55a with ejection failures. When the size is less than the second threshold value, the control device 20 can determine a flushing or wiping with a weaker improvement power than the purge as the first cleaning to be executed. When a purge is determined as the first cleaning, after the control device 20 is switched from the non-coated state to the coated state by the switching mechanism 59, the control device 20 causes the pump 52 as the first cleaning unit CL1 to execute a purge in the non-contact liquid state and the coated state. The control device 20 may change the suction force of the pump 52 in the purge according to the result of the above detection. In this case, the control device 20 can increase the suction force by increasing the driving time of the motor of the pump 52 and decrease the suction force by shortening the driving time. Also, the control device 20 can increase the suction force by increasing the rotation speed of the motor of the pump 52 and decrease the suction force by decreasing the rotation speed. Thereby, the ejection function is improved with an appropriate suction force according to the result of the above detection.

[0055] Alternatively, instead of the position distribution of the nozzles 55a where ejection defects occur, the control device 20 may determine the first cleaning to be executed among multiple types of first cleanings according to the number of times the first cleaning has been performed. In this case, when the number of times the first cleaning has been performed is less than the third threshold value, for example, the first cleaning with strong improving power is executed by the first cleaning unit CL1. On the other hand, when the number of times the first cleaning has been performed is equal to or greater than the third threshold value, for example, an error display is performed by the display unit 29. Thereby, an appropriate improvement of the ejection function according to the number of times the first cleaning has been performed is carried out, and an error display is performed in cases where the ejection function does not improve even if the first cleaning is repeated, thus avoiding unnecessary repetition of the first cleaning.

[0056] Also, in the present embodiment, after being switched from the liquid contact state to the non-liquid contact state by the switching mechanism 59 as described above and before the detection process for ejection defects is executed, the control device 20 causes the second cleaning unit CL2 to execute the second cleaning. Thereby, the cleaning liquid that has entered the nozzle 55a due to liquid contact is discharged by the second cleaning. Thereby, before the detection process for ejection defects is performed, the possibility that the ejection defects of the nozzle 55a are improved and the first cleaning becomes unnecessary is increased. Also, when the ejection function is not improved by the second cleaning, the ejection function may be improved by the first cleaning.

[0057] FIG. 7 is a flowchart showing the flow of the first cleaning and the second cleaning in the printing apparatus 100. As shown in FIG. 7, when the control device 20 receives a switching instruction based on a program, for example, it switches from the liquid contact state to the non-liquid contact state by the switching mechanism 59 (step S1).

[0058] Next, the control device 20 causes the second cleaning unit CL2 to perform the second cleaning (step S2). In this case, for example, when the non-discharge time (non-printing time) during which ink droplets are not discharged from the nozzle 55a is equal to or longer than a predetermined time, the control device 20 can perform a relatively strong flushing with an improved force as the second cleaning. Also, when the non-discharge time (non-printing time) is less than the predetermined time, the control device 20 can perform a relatively weak wiping with an improved force as the second cleaning. Note that both wiping and flushing may be performed as the second cleaning after switching from the liquid contact state to the non-liquid contact state.

[0059] Next, the control device 20 executes the detection process for discharge failure as described above (step S3). Then, the control device 20 determines whether or not to execute the first cleaning based on the result of the detection process (step S4). In this case, the control device 20 determines whether or not to execute the first cleaning according to, for example, the number of nozzles 55a in which discharge failure has occurred.

[0060] When it is determined that the first cleaning is necessary (Yes in step S4), the control device 20 determines whether or not the number of executions of the first cleaning is equal to or more than a third threshold value (step S5). In this case, the number of executions of the first cleaning is counted each time the first cleaning is completed. On the other hand, when it is determined that the first cleaning is unnecessary (No in step S4), the process ends.

[0061] When the number of executions of the first cleaning is less than the third threshold value in the process of step S5 (No in step S5), next, the control device 20 determines the first cleaning to be executed (step S6). In this case, the control device 20 determines the first cleaning to be executed according to, for example, the size of the range related to the position distribution of the nozzles 55a in which discharge failure has occurred or the number of times the first cleaning has been executed. On the other hand, when the number of executions of the first cleaning is equal to or more than the third threshold value in the process of step S5 (Yes in step S5), the control device 20 causes, for example, an error display to be made on the display unit 29 (step S8), and then ends the process.

[0062] After the process of step S6, the control device 20 causes the first cleaning unit CL1 to execute the determined first cleaning (step S7). After the process of step S7 ends, the control device 20 returns to the process of step S3 described above and repeats the subsequent processes. Note that the number of executions of the first cleaning is reset when it is determined that the first cleaning is unnecessary or when an error display is performed.

[0063] As described above, according to the printing apparatus 100 of the present embodiment, the control device 20 determines whether the first cleaning is necessary based on the detection result of the ejection failure of the nozzle 55a. When it is determined that the first cleaning is necessary, the first cleaning is executed by the first cleaning unit CL1, and when it is determined that the first cleaning is unnecessary, the first cleaning is not executed. Thereby, compared with the case where cleaning such as purge processing is uniformly performed regardless of the presence or absence of ejection failure of the nozzle, the amount of ink discharged from the inside of the nozzle 55a is reduced. As a result, the consumption of ink can be suppressed. In addition, since the liquid contact process is periodically performed in the printing apparatus 100, it is possible to suppress the thickening of the ink in the nozzle 55a. Thereby, in the first cleaning (such as purge) performed after the liquid contact state is formed, the ink in the nozzle 55a is easily discharged. Therefore, the amount of ink discharged can be reduced compared to the case where the ink in the nozzle 55a is forcibly discharged without the nozzle surface 55b contacting the liquid surface. Therefore, further suppression of ink consumption is achieved. In particular, when white ink containing pigment particles and having high thickening property is used, when, for example, purge is executed as the first cleaning, the amount of ink discharged in the purge increases, so that ink consumption becomes remarkable. However, as described above, the first cleaning is not uniformly executed but is executed only when necessary, so that the consumption of white ink can be suppressed.

[0064] Also, in the present embodiment, after being switched from the liquid contact state to the non-liquid contact state by the switching mechanism 59 and before the detection process for the discharge failure of the nozzle 55a is executed, the second cleaning unit CL2 executes the second cleaning. In this case, the liquid that has entered the nozzle 55a due to liquid contact can be discharged by the second cleaning. As a result, the possibility that the discharge failure is improved before the detection process for the discharge failure is performed and the first cleaning becomes unnecessary increases. Further, if the discharge function is not improved by the second cleaning, the discharge function can be improved by the first cleaning.

[0065] Also, in the present embodiment, the first cleaning includes a cleaning that has a stronger ability to improve the discharge function of the nozzle 55a than the second cleaning. In this case, for the nozzle 55a whose discharge function is not improved by the second cleaning, the discharge function can be improved by the first cleaning.

[0066] Also, in the present embodiment, according to the result of the detection of the discharge failure, the control device 20 determines the first cleaning to be executed among a plurality of types of first cleanings, and the first cleaning unit CL1 executes the first cleaning. As a result, among a plurality of types of first cleanings, for example, the first cleaning with a strong or weak ability to improve the discharge function is determined by the control device 20 according to the detection result of the discharge failure, and the determined first cleaning is executed by the first cleaning unit CL1.

[0067] Also, in the present embodiment, as a result of the detection of the discharge failure, specifically, according to the position distribution of the nozzles 55a where the discharge failure has occurred, the control device 20 determines the first cleaning to be executed. In this case, if the position distribution of the nozzles 55a where the discharge failure has occurred is wide, the first cleaning with a strong improvement ability can be executed by the first cleaning unit CL1. On the other hand, if the position distribution of the nozzles 55a is narrow, the first cleaning with a weak improvement ability can be executed by the first cleaning unit CL1. Thereby, an appropriate improvement of the discharge function is performed according to the position distribution of the nozzles 55a where the discharge failure has occurred.

[0068] Furthermore, in this embodiment, after being switched from the non-coated state to the coated state by the switching mechanism 59, as the first cleaning, purging is performed by the first cleaning unit CL1 in the non-liquid contact state and the coated state. In this case, a negative pressure is generated in the cap 51 by purging, and the ink in the nozzle 55a is discharged. Thereby, the first cleaning with strong improving power is performed.

[0069] The present disclosure is not limited to the above-described embodiments, and it is possible to adopt modifications without departing from the gist of the present disclosure. For example, it is as follows.

[0070] In the above embodiment, a path for forming dots along the first direction Dx1 and an operation of transporting the printing medium W in the transport direction Dy1 are repeated to form a predetermined image on the printing medium W. However, the printing method is not limited to this. As another printing method, a process of moving a carriage supporting the ejection head to a predetermined position in the first direction Dx, and in this state, a process of ejecting ink droplets from the ejection head while reciprocating a platen supporting the printing medium in the second direction Dy may be alternately repeated.

[0071] Also, in the above embodiment, after being switched from the liquid contact state to the non-liquid contact state by the switching mechanism 59 as described above and before the detection process of ejection failure is executed, the second cleaning is configured to be executed by the second cleaning unit CL2. However, the second cleaning is not an essential step.

[0072] In the above-described embodiment, the control device 20 determines the first cleaning to be executed among multiple types of first cleanings according to the position distribution of the nozzles 55a where ejection failure occurs or the number of times the first cleaning has been performed. However, the present invention is not limited to this. When determining the first cleaning to be executed among multiple types of first cleanings, the control device 20 may use the number of nozzles 55a where ejection failure occurs as a reference. In this case, a fourth threshold value larger than the first threshold value used when determining the necessity of executing the first cleaning as described above is used. That is, regarding the determination of the necessity of the first cleaning, the reference threshold value is set small, while regarding the determination of the type of the first cleaning to be executed, the reference threshold value can be set large. In this case, the control device 20 compares the number of nozzles 55a related to ejection failure with the predetermined fourth threshold value. When the number of nozzles 55a related to ejection failure is equal to or greater than the fourth threshold value, for example, a purge with strong improvement power can be determined as the first cleaning to be executed. Also, when the number is less than the fourth threshold value, the control device 20 can determine a flushing or a wipe with weaker improvement power than the purge as the first cleaning to be executed. Thereby, an appropriate improvement of the ejection function according to the number of nozzles 55a where ejection failure occurs is performed.

[0073] Furthermore, in the above-described embodiment, the position of the cap 51 when the covering state is formed is made the same as the position of the cap 51 when the liquid contact state is formed. However, the present invention is not limited to this. When the liquid contact state is formed, if the condition that the nozzle surface 55b comes into contact with the liquid is satisfied, the nozzle surface 55b does not have to be covered by the cap 51.

Explanation of Reference Numerals

[0074] 20 Control device 41 Wiping unit 42 Moving mechanism 52 Pump 53 Lifting mechanism 55 Ejection head 55a Nozzle 55b Nozzle surface 56 Actuator 59 Switching mechanism 100 Printing device CL1 First cleaning section CL2 Second cleaning section Pa Uncap position Pc Cap position W Printed medium

Claims

1. A discharge head having a nozzle surface provided with a plurality of nozzles; A switching mechanism that switches between a liquid contact state in which a predetermined liquid level is brought into contact with the nozzle surface and a non-liquid contact state in which the nozzle surface is separated from the liquid level when ink is not discharged from the nozzles; A first cleaning unit that performs a first cleaning which is a cleaning for improving the discharge function of the nozzles; A control device, and comprising: The control device: A process of switching from the liquid contact state to the non-liquid contact state by the switching mechanism; After being switched to the non-liquid contact state, a process of detecting a discharge failure of at least one of the nozzles on the nozzle surface; A process of determining the necessity of the first cleaning based on the result of the detection; and executes When it is determined that the first cleaning is necessary, the first cleaning unit is made to execute the first cleaning; A printing apparatus that does not cause the first cleaning unit to execute the first cleaning when it is determined that the first cleaning is unnecessary.

2. A second cleaning unit that performs a second cleaning which is a cleaning for improving the discharge function of the nozzles is provided, After being switched from the liquid contact state to the non-liquid contact state by the switching mechanism and before executing the process of detecting a discharge failure of the nozzles, the control device causes the second cleaning unit to execute the second cleaning. The printing apparatus according to claim 1.

3. The printing apparatus according to claim 2, wherein the first cleaning includes a cleaning having a stronger discharge function improving power than the second cleaning.

4. The first cleaning includes a plurality of types of first cleaning, The control device determines the first cleaning to be executed among the plurality of types of first cleaning according to the result of the detection and causes the first cleaning unit to execute it. The printing apparatus according to claim 1.

5. The control device determines the first cleaning to be executed according to the number of the nozzles in which a discharge failure has occurred as a result of the detection. The printing apparatus according to claim 4.

6. The control device determines the first cleaning to be executed according to the position distribution of the nozzles in which a discharge failure has occurred as a result of the detection. The printing apparatus according to claim 4.

7. The first cleaning includes a plurality of types of first cleaning, The printing apparatus according to claim 1, wherein the control device determines a first cleaning to be executed among the plurality of types of first cleanings according to the number of times the first cleaning has been executed, and causes the first cleaning unit to execute the determined first cleaning.

8. The switching mechanism switches between a covered state in which the nozzle surface is covered by the switching mechanism and a non-covered state in which the nozzle surface and the switching mechanism are separated from each other. The printing apparatus according to claim 1, wherein after the switching mechanism switches from the non-covered state to the covered state, as the first cleaning, the control device causes the first cleaning unit to execute a purge for forcibly discharging ink from the nozzles in the non-contact liquid state and in the covered state.

9. The first cleaning unit has a pump that generates a negative pressure in the switching mechanism when the purge is executed. The printing apparatus according to claim 8, wherein the control device changes the suction force of the pump in the purge according to the result of the detection.

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