JP5487715B2 - Printing apparatus and ink channel cleaning control method. - Google Patents

Description

  The present invention relates to a printing apparatus including a head for ejecting a plurality of colors of ink onto a medium. The present invention also relates to an ink flow path cleaning method in the printing apparatus.

  2. Related Art Inkjet printers that perform printing by intermittently ejecting ink are known as printing apparatuses that print images on various printing media (hereinafter referred to as media) such as paper, cloth, and film. In a general printing operation in an ink jet printer, a medium is moved in a specific transport direction, and a head including a nozzle from which ink is ejected is reciprocated in a scanning direction intersecting the transport direction. In this way, ink is ejected from the nozzles while moving the medium and the head, and the ink is landed at a target position on the surface of the medium to form an image.

  The ink is filled in an ink tank. After being guided from this tank to a space called a reservoir in the head by a pump, the ink is guided from the reservoir to a pressure chamber communicating with the nozzle. Ink is ejected from the nozzles by expanding and contracting the pressure chamber.

  By the way, there is what is called white “white ink” among inks used in ink jet printers. For example, when printing on a transparent medium, this ink is used to prevent a background part that is not originally printed or a color of a color image from being influenced by a color behind the medium. The white ink has such a property that after landing on the medium, it is quickly dried and fixed on the medium. On the other hand, when the power of the inkjet printer is turned off, if such white ink remains in any of the channels from the tank to the nozzle, the white ink is dried and fixed in the channel. Has the problem of causing clogging.

  Therefore, in an ink jet printer using white ink, when the printer is turned off, the flow path is filled with transparent ink for preventing clogging called clear ink which is difficult to dry instead of white ink, Some have a mechanism for preventing clogging by white ink remaining in the flow path. The following Patent Document 1 describes a printer having such a mechanism. Patent document 2 describes the characteristics of white ink.

JP 2008-162023 A JP 2003-313481 A

  As in the printer described in Patent Document 1, when the power is turned off, the white ink channel is filled with clear ink, and when printing is performed, the white ink is filled into the channel again and discharged toward the medium. In this case, the original lightness (L value) of the ink on the medium can be obtained at the beginning of the ejection, but after printing using the white ink, for example, images without using the white ink are continuously printed. If the white ink is discharged again after a while without turning off the power, the clear ink is mixed in the discharged white ink, and the L value of the white decreases when printing with the white ink is resumed. The problem was discovered.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a printing apparatus capable of selectively filling a flow path with easily dried color ink such as white ink and clogging prevention ink. An object of the present invention is to provide a printing apparatus capable of reducing deterioration in print image quality due to mixing of ink for preventing clogging even when printing is performed using color inks intermittently. Other purposes will be clarified below.

The main present invention for achieving the above object includes a head for ejecting a plurality of colors of ink onto a medium ,
A filling chamber provided in the head for individually filling the ink of each of the plurality of colors;
A flow path switching mechanism for selectively filling the filling chamber corresponding to the specific ink of a predetermined color with the specific ink and the clogging prevention ink;
A control unit for controlling the flow path switching mechanism and the head;
A printing apparatus comprising:
Wherein the control unit executes a first switching process, a second switching process, a printing operation of ejecting the specific ink on the medium, and the ink use amount obtaining process, and the flow path cleaning process, and
In the first switching process, switching from the first filling state in which the head is filled with the specific ink to the second filling state in which the head is filled with the clogging prevention ink,
In the second switching process, switching from the second filling state to the first filling state,
In the ink usage amount acquisition process, the cumulative usage amount of the specific ink used until the printing operation executed after the execution of the second switching process is interrupted is acquired,
In the flow path cleaning process, after the printing operation executed after the execution of the second switching process is interrupted , when the printing operation is resumed without passing through the second filling state , the ink usage amount When the accumulated usage amount of the specific ink acquired in the acquisition process is less than a predetermined amount, the specific ink is ejected to be discarded in a predetermined procedure.
It is characterized by that. The other features of the present invention will be clarified by the description of the present specification and the accompanying drawings.

1 is a block diagram of a printer 1 according to an embodiment. 1 is a perspective view showing an outline of a printer. It is a figure which shows the arrangement | sequence of the nozzle formed in the head which comprises a printer. It is a structural diagram of the filling chamber built in the head. 2A and 2B are cross-sectional views of the head, wherein FIG. 1A is a cross-sectional view when cut in a direction crossing the nozzle row, and FIG. 2B is a vertical cross-sectional view of a nozzle row for white ink. It is a figure which shows the outline of the ink suction unit which comprises the said printer. 2A and 2B are perspective views of the printer, in which FIG. 1A illustrates a state where a carriage constituting the printer is positioned on the opposite side of the home position, and FIG. 2B illustrates a state where the carriage is positioned at the home position. FIG. It is a figure which shows the flow of the flow-path washing | cleaning operation | movement in 1st Example of this invention. It is a figure which shows the content of the flow-path washing | cleaning operation | movement in 1st Example of this invention. It is a figure which shows the content of the flow-path washing | cleaning operation | movement in the 2nd Example of this invention. It is a figure which shows the flow of the flow-path washing | cleaning operation | movement in the example of a change of this invention.

=== Features of the Invention ===
As described above, in a printing apparatus that uses quick-drying ink such as white ink, clogging may occur if the ink is left in the flow path. In the conventional printing apparatus, when the power is turned off, the ink for preventing clogging is filled in the flow path of the quick-drying ink (specific ink). When the power is turned on again and it becomes necessary to print by ejecting the specific ink onto the medium, the flow path is switched to the specific ink side, the specific ink is sucked, and the clogging prevention ink in the flow path flows. After discarding outside the road, the printer shifts to a printing operation using specific ink. Accordingly, the clogging prevention ink is prevented from being mixed into the specific ink, thereby preventing the L value of the specific ink from being lowered.

  However, at the beginning of discharging the white ink as the specific ink, a good print image can be obtained with a high L value, but after printing with the white ink, after a while, the white ink is discharged again, The inventor has found that the L value decreases. Therefore, we tried to clarify the mechanism of such phenomena. And the following conclusion was obtained.

  First, when the flow path is switched to the path from the tank on the white ink side in order to print white ink with the clogging prevention ink filled in the flow path, the white ink is sucked at that time. At this time, the flow rate of the ink in the flow path is high, and the white ink is discharged before the clear ink remaining in the flow path is completely replaced with the white ink. For this reason, for example, the clear ink remains in a portion where the flow velocity is low, such as a wall surface side of the flow path or a corner of a space (for example, a reservoir) filled with ink.

  After discharging white ink, if the white ink channel is not filled with clear ink and a pause occurs, the clogging prevention ink remaining in the channel during the pause is gradually The amount of ink for preventing clogging is relatively increased by mixing with the white ink. If white ink is ejected in this state, the L value will deteriorate.

  Based on this conclusion, when printing using white ink again after a pause, if the inside of the white ink flow path is washed by well-known flushing or the like, and the clear ink is discarded together with the white ink, It is considered that the decrease of the L value can be prevented. However, if the flow path is washed each time printing with white ink is resumed, the ink is wasted.

  Therefore, further investigations were made on measures to keep the white ink discarded by cleaning the flow path to the minimum necessary. Then, he noticed that there was little deterioration in the L value while printing using white ink. This is because when printing with white ink, the white ink moves to the nozzles at a high speed in almost the shortest path, so the clear ink remaining in the corner of the flow path has a sufficient time to mix with the white ink. No. As a result, the amount of clear ink is relatively small with respect to the amount of white ink to be ejected, and the model that the L value does not deteriorate significantly can be explained.

  The present invention has been created based on the above-described findings. In addition to the main invention, the present invention extends to a printing apparatus having the following features.

  A storage unit is provided for storing a correspondence between a cumulative usage amount of the specific ink and a procedure for discharging the specific ink, and the flow path cleaning process corresponds to the acquired cumulative usage amount of the specific ink. Discharging in order to discard the specific ink.

The present invention also extends to an ink flow path cleaning control method in a printing apparatus. The invention according to the method includes a head for ejecting a plurality of colors of ink onto a medium, the head is provided with the head, A filling chamber for individually filling a plurality of colors of ink, and a filling chamber corresponding to a specific ink of a predetermined color for selectively filling the specific ink and the clogging prevention ink. An ink flow path cleaning control method in a printing apparatus comprising a flow path switching mechanism and a control unit for controlling the flow path switching mechanism,
A first switching step of switching from a first filling state in which the head is filled with the specific ink to a second filling state in which the head is filled with the clogging prevention ink;
A second switching step for switching from the second filling state to the first filling state;
An ink usage amount acquisition step of acquiring a cumulative usage amount of the specific ink used for printing after the execution of the second switching step;
After executing the second switching process, after printing with the specific ink, when resuming printing with the specific ink without passing through the second filling state, the accumulated usage amount of the acquired specific ink is greater than a predetermined amount. If less, a flow path cleaning step for discharging the specific ink in a predetermined procedure;
It is characterized by including.

=== Embodiment of the Invention ===
As an embodiment of a printing apparatus according to the present invention, an ink jet printer (hereinafter referred to as a printer) capable of printing using white ink is given. FIG. 1 is a block diagram of the overall configuration of the printer 1. The controller 60 is a main control unit, and includes a transport unit 20, an ink suction unit 30, a head unit 40, and a detector group 50 as main components.

  The controller 60 is a control unit for controlling the printer 1 and includes a CPU 62, which is an arithmetic processing unit, a RAM, an EEPROM, and the like, and secures a storage area for a program executed by the CPU 62 and a work area for the program. A memory 63, a unit control circuit 64 for driving each unit (20, 30, 40), an interface unit (IF) 61 for mediating data communication between the computer 100 and the CPU 62 as an external device, and the like. It consists of

  FIG. 2 is a cutaway perspective view of the printer 1. In this figure, the overall configuration of the printer 1 is shown in a simplified manner. The head unit 40 includes a carriage 42 for moving the head 41 in the scanning direction, an ink cartridge 43 filled with ink, and the like. The carriage 42 is guided by the carriage guide shaft 44 and is reciprocated in the scanning direction by being pulled by the index belt 46 driven by the carriage motor 45. In order to perform multicolor printing, ink of a plurality of colors including white ink is individually filled in the ink cartridge 44, and each ink cartridge 43 corresponding to each color is detachably mounted on the carriage 42. .

  The transport unit 20 is a mechanism for transporting the medium S, and includes a transport motor 21 and a transport roller 22 driven by the transport motor 21. The medium S moves in the transport direction perpendicular to the scanning direction of the carriage 48 by the transport unit 20. As a result, the lower surface of the head 42 can face the arbitrary position on the surface of the medium S.

  The head 41 is configured to eject ink droplets toward the medium S, and a plurality of nozzles 71 are opened on the lower surface thereof. FIG. 3 illustrates the arrangement of the nozzles 70. On the lower surface 47 of the head 41, a plurality of nozzles 71 are opened at regular intervals along the transport direction, and nozzle rows (48W, 48K, 48C, 48C, 48C, 48C, 48C) corresponding to the respective colors of white, black, cyan, magenta, and yellow. 48M, 48Y). In the printer 1 shown here, 360 nozzles 71 are provided for each color, and a total of 360 × 5 = 1800 nozzles are provided. Further, as shown in FIG. 4, the inks of the respective colors are led from the respective ink cartridges 42 to the individual reservoirs 72 for the respective colors via the pipes 81 and stored therein. In the printer 1, the ink circulation section from the reservoir 72 to the nozzle 71 is a filling chamber 70.

  Each color ink stored in the reservoir 72 is further guided to a pressure chamber 73 communicating with the nozzle 71 via a supply path 74. The pressure chamber 73 corresponds to one nozzle 71 on a one-to-one basis. That is, there are as many nozzles 71 as there are. A piezo element 75 is individually attached to each pressure chamber 73, and when the piezo 75 element is driven, the pressure chamber 73 expands and contracts and an ink droplet is ejected from the nozzle 71.

  In the printer 1 having the above-described configuration, the CPU 62 in the controller 60 executes the program stored in the memory 63, thereby printing data received from the computer 100 via the IF 61 and the detector group 50. The detection data and the like are processed, and each unit (20, 30, 40) is controlled by the unit control circuit 64 based on the processing result. With this control, the head 41 discharges ink droplets intermittently from the nozzle 71 while moving in the scanning direction integrally with the carriage 42. Thereby, a dot line (raster line) along the scanning direction is formed on the medium S, and a print image is formed on the medium S.

=== Print mode ===
The printer 1 according to the present embodiment performs printing using a monochrome printing mode in which printing is performed using only black ink, a color printing mode in which printing is performed using color ink other than white, and white ink. A white printing mode is provided. That is, white ink is not used in operation modes other than the white printing mode. When the printer 1 is turned off after printing in the white printing mode, the clogging prevention ink (hereinafter, clear ink) is filled in the white ink flow path, and the printer 1 is turned off and left as it is. In this case, the white ink has a function of preventing clogging due to white ink adhering to the flow path.

=== Characteristics of white ink ===
As the white ink used in the present embodiment, for example, the one described in Patent Document 2 can be adopted. The white ink described in this document is an aqueous pigment ink, and uses a hollow resin for the pigment. When this hollow resin exists in the form of liquid ink, the hollow portion (cavity) is filled with moisture, and when the ink is ejected and adheres to the medium, the moisture in the hollow portion (cavity) evaporates and dries quickly. Fix on the medium. And a hollow part (cavity) is filled with air. The size of the hollow portion (cavity) is designed to scatter visible light so that the ink fixed on the medium looks effectively white.

=== Ink replacement function ===
As described above, the printer 1 according to the present embodiment includes the white printing mode, and the white ink used in the white printing mode has a quick drying property due to the structure described above. That is, if the white ink remains in the flow path, the flow path may be clogged. For this purpose, the printer 1 has an ink replacement function for discarding white ink remaining in the flow path and filling the white ink flow path with clear ink when the power is turned off. Hereinafter, the ink replacement function will be described.

<Flow path switching operation>
FIG. 5 is a cross-sectional view of the head shown in FIG. 3A is a cross-sectional view taken along the line aa in FIG. 3, and shows a state in which the head 41 is cut in a scanning direction at a specific row portion of each color nozzle row (48W, 48K, 48M, 48C, 48Y). It corresponds to a cross section. FIG. 3B is a cross-sectional view taken along the line bb in FIG. 3, and shows a vertical cross section of the white ink row 48W. In FIG. 5B, for ease of explanation, the structure of the head 41 is represented by seven nozzles 71 which are smaller than the actual number of nozzles 71. 5 also includes an ink cartridge 43 and ink flow paths (81W, 81CL, 81C, 81Y, 81M, 81K) from the ink cartridge 43.

  As previously shown in FIG. 4, the reservoir 72 is a chamber communicating with the pressure chamber 73 via the supply path 74. The reservoir 72 is for storing ink, and is provided for each of the five colors of ink (for each color), and the pressure chamber is provided for each nozzle 71. An ink cartridge 43 is detachably connected to the reservoir 72 of the head 41. The ink in the ink cartridge 43 is supplied to the reservoir 72 and finally filled into the flow path that forms the filling chamber 70 up to the nozzle 71. Further, in this example, the reservoir 72 is curved downward toward a portion corresponding to both ends 72a of the nozzle row 48W, and has a generally arch-shaped vertical cross-sectional shape. When the vicinity 72a of both ends of the nozzle row 48W is outside the path through which the ink flows into the pressure chamber 73 via the supply path 74, and the vertical cross-sectional shape of the reservoir 72 is a simple rectangle, the ink is applied to both ends of the reservoir 72. Tends to stay. If the clear ink stays here, it will be mixed with the white ink and cause the L value to deteriorate. Therefore, the portion 72a is curved toward the supply path 74 to prevent the retention of clear ink as much as possible.

  By the way, as described above, the white ink channel needs to be filled with clear ink when the power is turned off. In the printer 1, therefore, two ink cartridges (43 W, 43 CL) of white ink and clear ink are connected to the reservoir 72 for white ink, and each of the two ink cartridges (43 W, 43 CL) is connected. The inflow conduits (81W, 81CL) are configured to join one outflow conduit 81 communicating with the reservoir 72 via the flow path switching mechanism 80 in the middle. The flow path switching mechanism 80 can be configured by, for example, a 2-input 1-output switching valve. Alternatively, a port to which one of the two inflow pipes (81W, 81CL) is connected to the entrance of the outflow pipe 81 is connected, and one of the two inflow pipes (81W, 81CL) is connected to the port. It can also be configured by a mechanism for In any case, the printer 1 includes a mechanism 80 that selectively connects one of the two inflow conduits (81W, 81CL) to the outflow conduit 81 under the control of the controller 60. Thereby, one of white ink and clear ink is selectively supplied to the filling chamber 70.

<Ink suction operation>
In order to fill the filling chamber 70 with ink, it is necessary to suck the ink from the cartridge 43 toward the nozzle 71. And the structure for that is an ink suction unit. Further, in order to replace the white ink in the filling chamber 71 with the clear ink, it is necessary to discard the white ink remaining in the white ink flow path including the filling chamber 70 outside the flow path. FIG. 6 shows the structure of a suction unit for sucking ink. FIG. 7 shows the printer 1 in a state where the carriage 42 is at a different position from the printer 1 shown in FIG. 7A and 7B, when the carriage 48 reciprocates left and right with the left-right direction as the scanning direction, the carriage 48 is positioned at either the left or right end of the moving range. The position of the carriage 48 shown in FIG. 7A is a standby position when the power is turned off, that is, the home position of the carriage 48. As shown in (B), the ink suction unit 32 is provided to face the head 42 when the carriage 48 is at the home position.

  The ink suction unit 30 shown in FIG. 6 is configured to perform a flow path cleaning operation that actively distributes ink that is not involved in printing to the ink flow path and eliminates the ejection failure of the head 41. A head cap 31, a hose 33, and a suction pump 34 are provided. The head cap 31 has a structure in which a box-shaped internal space is partitioned into five suction chambers 32 corresponding to the nozzle rows of the respective colors (five colors), the side facing the head 41 is opened, and each partition is formed on the lower surface. A hose 33 communicating with each other is connected. The head cap 31 is configured to be able to move up and down, and ascends to contact the lower surface 47 of the head 41 and closes the opening of the nozzle 71.

  The suction pump 34 is provided for each hose 33, and is a disk-shaped large roller 35a that is rotated by a motor, and two small rollers 35b that protrude from the surface of the large roller 34a in the vicinity of both ends of the diameter of the large roller 35a. It has a structure with. A hose 33 is wound around the two small rollers 35b.

  The hose 33 has one end connected to the bottom surface of the head cap 31 and the other end opened. When the large roller 35a rotates in the direction of the arrow in the figure with the head cap 31 closing the nozzle 71 opening, the air in the hose 33 is pushed by the small roller 35b, and each suction chamber in the head cap 31 is pressed. The air in 32 is exhausted from the other end of the hose 33. With this exhaust, each suction chamber 32 becomes negative pressure, and the ink in the filling chamber 70 of the head 41 is sucked and guided to the individual suction chamber 32 for each color ink through the nozzle 71. Finally, it is discarded in a waste ink discharge section (not shown) continuous to the other end of the hose. The head cap 31 is in a raised state when printing is not performed and the carriage 42 is located at the home position, and functions as a lid that is in close contact with the lower surface 47 of the head 31 and closes the opening of the nozzle 71. Thus, the ink is prevented from drying in the filling chamber 70 due to the opening of the nozzle 71 coming into contact with the outside air during the printing pause.

=== About Flushing Operation ===
In the ink jet printer 1, in order to keep the ink in the head 41 in a fresh state, an operation called flushing for ejecting ink that is not involved in printing is performed. The flushing is executed until the carriage 42 performs an operation of ejecting ink for the purpose of image printing from the home position to the medium S during execution of the printing process.

  The flushing operation will be described with reference to FIG. 7. The printer 1 is provided with a flushing box 36 adjacent to the ink suction unit 30. The flushing box 36 is at a position where the carriage 42 has moved slightly from the home position. That is, in the flushing, the carriage 42 is moved so that the lower surface 47 of the head 41 faces the flushing box 36, the piezo element 75 is driven by a flushing drive signal at this position, and ink from the nozzle 71 is flushed. It is executed by the procedure of discharging toward the water. The ink discharged toward the flushing box 36 is discharged to the waste ink discharge unit.

=== Embodiment of the Invention ===
The printer 1 selects either the white ink or the clear ink in the filling chamber 70 by executing an operation (channel cleaning operation) appropriately combining the above-described channel switching operation with the suction operation and the flushing operation. In order to prevent clogging caused by white ink when the power is turned off and when the white print mode is executed intermittently, clear ink in the flow path is surely discharged to prevent a decrease in L value. It has a function to do. However, the printer 1 according to the present embodiment considers the amount of clear ink remaining in the filling chamber 70 in accordance with the amount of white ink used, and performs the above-described clogging and L value with the minimum required flow path cleaning operation. Is prevented. Hereinafter, in the printer 1 according to the present embodiment, a method (flow path cleaning control method) for suppressing a decrease in the L value while reducing the amount of white ink to be discarded is an example of the present invention.

=== First Embodiment ===
In the first embodiment of the present invention, when shifting from the white printing mode to the other printing mode and then returning to the white printing mode again, the cumulative amount of white ink used in the white printing mode is less than a predetermined amount. In some cases, the white ink flow path is cleaned.

  FIG. 8 shows the procedure of the flow path cleaning operation in the first embodiment. It is assumed that the power is once turned off and the white ink flow paths (81, 70) are filled with clear ink. When the CPU 62 is turned on and further receives a print instruction in the white print mode from the external computer 100, the CPU 62 controls the flow path switching mechanism 80 so that the conduit 81W from the white ink cartridge 43W is supplied to the reservoir. To the pipe 81. At this time, first, a flow path cleaning operation at the time of switching is performed. When the flow path cleaning operation at the time of switching is completed, printing is started using white ink (s1 to s4). Then, measurement of the amount of white ink used is started from the point of time when printing with this white ink is started, and the accumulated value of the amount of use is stored in the memory 63 (s5, s6).

  Next, after printing with white ink is interrupted, such as printing another color or waiting until the next print command is received with the power turned on, switch to the white print mode again. When activated, the accumulated amount of white ink stored so far in the memory is acquired (s7 → s8 → s9). If the accumulated usage amount is less than the predetermined amount stored in the memory 63 in advance, the white ink flow path is washed by a predetermined procedure (s10 → s11). If the amount is equal to or greater than the predetermined amount, printing in the white print mode is started without performing the channel cleaning operation. Also in the second white printing mode, the accumulated amount of white ink is updated as needed (s12 → s6). Then, when the white printing mode is ended and the third white printing mode is started, similarly, if the accumulated amount of white ink used is less than the predetermined amount, the flow path cleaning operation is executed (s7 → s8 → s9, s10 → s11). When a power-off command is received from the external computer 100, the flow path switching mechanism is controlled to connect the white ink filling chamber 70 and the clear ink flow path 81CL and operate the ink suction unit 30. The filling chamber 70 is filled with clear ink, and the power is turned off (s8 → s12 → s13, s14).

  FIG. 9 shows the contents of the channel cleaning operation in the first embodiment. The flow path cleaning operation at the time of switching and the flow path cleaning operation to be executed when the white printing mode is resumed when the accumulated amount of white ink used is less than a predetermined amount are shown. The contents of these flow path cleaning operations may be stored in the memory 63 in advance. In FIG. 9, (A) shows the contents of individual operations (ad) in the flow path cleaning operation. As individual operations (a to d), there are suction (a, b) and flushing (c, d). The flushing (c, d) further includes “all nozzle flushing” ( c) and “both-end flushing” (d) performed only for the nozzles at both ends of the nozzle row are defined. As shown in FIG. 5B, even if the shape of the reservoir 72 is a shape in which ink does not easily stay, compared to the middle portion of the same row 48W, the ink is not present in the portions 72a at both ends. Tends to stay. Therefore, the ink in the portion 72a that tends to stay is discharged as much as possible by ejecting ink intensively from the nozzles 71a at both ends of the nozzle row 48W.

  FIG. 9B shows the content of the flow path cleaning operation when the white printing mode is activated (when switching) and the content of the flow path cleaning operation when the white printing mode is resumed. The flow path cleaning operation at the time of resuming the white printing mode is executed only when the amount of white ink used in the immediately preceding white printing mode is less than a predetermined amount. Further, in FIG. 9B, the amount of ink discarded along with a series of operations is added for reference.

  As shown in FIG. 9, the ink suction amount and discharge amount indicated by g (grams) can be calculated based on, for example, the operation time of the suction pump as long as it is a suction amount. With respect to the ink ejection amount in the flushing, the number of times that the piezo element 75 is driven by a predetermined driving waveform and ink droplets are ejected from the nozzle 71, the amount of ejection performed once, the number of nozzles 71 that performed the ejection operation, It can be calculated based on the specific gravity of the ink. Of course, similarly, the cumulative amount of white ink used in the white printing mode can be calculated.

  In order to actually suck or discharge a predetermined amount of ink, the relationship between the operation time of the suction pump 34 and the suction amount, the driving condition of the piezo element 75, the ink discharge amount, and the like are stored in the memory 63. And the CPU 62 may cause the unit control circuit 64 to control the suction pump 34 and the piezo element 75 based on this relationship to suck or discharge a predetermined amount of ink.

  As described above, in the first embodiment, when the white printing mode is restarted after a pause, if the previous accumulated amount of white ink is less than a predetermined amount, the flow path cleaning operation is executed. Therefore, it is judged that the accumulated amount of white ink is large and the clear ink in the flow path is discharged as the white ink is discharged while reliably preventing the L value from being lowered due to the clear ink mixed into the white ink. If possible, it is possible to minimize the amount of white ink to be discarded by washing the flow channel without washing the flow channel.

=== Second Embodiment ===
In the first embodiment, when the amount of white ink used in the white printing mode is less than the threshold value, the flow path cleaning operation is executed when the white printing mode is activated again. In other words, if the amount of white ink used exceeds the threshold even slightly, the flow path cleaning operation is not executed. However, depending on the environment (temperature, humidity, etc.) in which the printing apparatus is placed, If different values are assumed, and a unique threshold value is set, the L value may decrease when the white printing mode is resumed.

  Therefore, in the second embodiment, different flow path cleaning operations are performed according to the amount of white ink used. FIG. 10 shows the contents of the flow path cleaning operation in the second embodiment. (A) sets the details of each cleaning operation in more detail, and, as shown in (B), defines the combination of cleaning operations according to the cumulative usage. In (C), the content of each cleaning operation differs depending on the cumulative usage. For example, as shown in FIG. 9B, the combination of the cleaning operations is substantially different in the content of the channel cleaning operation according to the accumulated usage amount as shown in FIG. The procedure of the flow path cleaning operation in the second embodiment is only that the flow path cleaning operation of s11 is executed with the content corresponding to the accumulated amount of white ink in the flowchart shown in FIG. Will be different.

  As described above, in the second embodiment, it is possible to reliably prevent the L value from being deteriorated without being influenced by the installation environment of the printing apparatus and the like, while minimizing the exhaust amount of the white ink.

=== Example of change ===
In the first embodiment, the accumulated amount of white ink required for printing is actually measured. Not limited to this example, the amount of white ink used can be calculated based on the data of the image to be printed. FIG. 11 shows the procedure of the flow path cleaning operation in the modified example with respect to each of the above embodiments. First, when the power is turned on and a printing instruction in the white printing mode is received, a flow path cleaning operation at the time of switching is executed (s21 to s23). Next, when printing using white ink is started, the amount of ink used is acquired based on the print data, and printing is performed in the white printing mode (s24, s25).

  When the printing in the white printing mode is resumed after the white printing mode is finished, an accumulated value of the ink usage until then is calculated. In this case, since the power is turned on and the second white printing mode is activated, the amount of white ink used in the previous (first) white printing mode is acquired as an accumulated value (s26 → s27 → s28). If the accumulated value is less than the predetermined amount, the flow path cleaning operation is executed (s29 → s30), and the amount of white ink used is acquired from the print data in the second white printing mode (s30 → s24). ).

  When the second white printing mode is completed and printing in the third white printing mode is resumed, is the flow path cleaning operation executed based on the accumulated values of the first and second white ink usage amounts? It is determined whether or not (s25 to s29). If the power-off command is received without restarting the white print mode, the clear ink is filled in the white ink flow path and the power is turned off (s27 → s31 → s32, s33).

  As described above, in this modified example, it is not necessary to perform a process of actually measuring the amount of ink used in parallel with the printing process of the white ink, and the processing added by the CPU 62 can be reduced. In other words, the CPU 62 is not required to have a higher processing capacity. Therefore, it is expected that the printer 1 can be provided at a low cost by adopting a cheaper CPU 62.

=== About ink ===
In the above embodiment, the example of cleaning the flow path of the white ink has been described. However, if the purpose is to prevent clogging even with other color ink, the ink of that color is placed in the flow path of that color. And clear ink may be selectively filled, and the flow path may be washed by the same method as in the above embodiment. For example, the black filling chamber may be selectively filled with either black ink or clear ink, and the black filling chamber may be filled with the clear ink when the printer is stopped. Of course, it is also possible to configure not only one color ink but also two or more or all color inks so that the respective channels can be filled with clear ink.

  It is also possible to use a low-viscosity color ink as a clogging prevention ink for a specific color ink. For example, there are cyan and light (light) cyan as the same color ink, but the cyan filling chamber is filled with light cyan ink as color ink, and cyan ink is filled as clogging prevention ink. May be.

=== About Form of Printing Apparatus ===
In the above embodiment, a piezoelectric inkjet printer that ejects fluid by applying a voltage to a drive element (piezo element) to expand and contract an ink chamber has been exemplified. Not limited to this, a thermal method may be used in which bubbles are generated in a nozzle using a heating element and liquid is ejected by the bubbles.

  The medium to be printed by the printing apparatus is not limited to paper, but may be in any form as long as it is printed with color ink, such as a cloth, a label surface of an optical disk (CD-R, etc.), or a substrate. Good. Of course, the medium may be continuously conveyed like roll paper, or individually conveyed like cut paper.

  The head of the printing apparatus may not be configured to move in the scanning direction, but may be configured to be fixed in a line shape over the width of the medium in the scanning direction, that is, the direction intersecting the transport direction. A so-called line printer may be used.

1 printer, 20 transport unit, 30 ink suction unit,
31 Head cap, 32 Suction chamber, 33 Hose, 34 Suction pump,
35a large roller, 35b small roller, 36 flushing box,
40 head units, 41 heads, 42 carriages,
43 ink cartridge, 44 guide rail, 45 carriage motor,
46 traction belts, 50 detector groups, 60 controllers,
61 interface unit, 62 CPU, 63 memory,
64 unit control circuit, 70 filling chamber, 71 nozzle, 72 reservoir,
73 pressure chamber, 74 supply path, 75 piezo element, 80 flow path switching mechanism,
100 computer, medium S

Claims (3)

A head for ejecting a plurality of colors of ink on a medium ;
A filling chamber provided in the head for individually filling the ink of each of the plurality of colors;
A flow path switching mechanism for selectively filling the filling chamber corresponding to the specific ink of a predetermined color with the specific ink and the clogging prevention ink;
A control unit for controlling the flow path switching mechanism and the head;
A printing apparatus comprising:
Wherein the control unit executes a first switching process, a second switching process, a printing operation of ejecting the specific ink on the medium, and the ink use amount obtaining process, and the flow path cleaning process, and
In the first switching process, switching from the first filling state in which the head is filled with the specific ink to the second filling state in which the head is filled with the clogging prevention ink,
In the second switching process, switching from the second filling state to the first filling state,
In the ink usage amount acquisition process, the cumulative usage amount of the specific ink used until the printing operation executed after the execution of the second switching process is interrupted is acquired,
In the flow path cleaning process, after the printing operation executed after the execution of the second switching process is interrupted , when the printing operation is resumed without passing through the second filling state , the ink usage amount When the accumulated usage amount of the specific ink acquired in the acquisition process is less than a predetermined amount, the specific ink is ejected to be discarded in a predetermined procedure.
A printing apparatus characterized by that. In claim 1,
Wherein with the accumulated amount of the specific ink, a storage unit for storing a correspondence of the procedure for discharge to discard the particular ink,
In the flow path cleaning process, the specific ink is discharged for disposal in a procedure corresponding to the cumulative usage of the specific ink acquired in the ink usage acquisition process .
A printing apparatus characterized by that. A head for ejecting a plurality of colors of ink on a medium;
A filling chamber provided in the head for individually filling the ink of each of the plurality of colors;
A flow path switching mechanism for selectively filling the filling chamber corresponding to the specific ink of a predetermined color with the specific ink and the clogging prevention ink;
A control unit for controlling the flow path switching mechanism and the head ;
An ink flow path cleaning control method in a printing apparatus comprising:
A first switching step of switching from a first filling state in which the head is filled with the specific ink to a second filling state in which the head is filled with the clogging prevention ink;
A second switching step for switching from the second filling state to the first filling state;
In printing by discharging the specific ink onto the medium, which is executed after the second switching step, the ink usage amount for acquiring the cumulative usage amount of the specific ink used until the printing is interrupted An acquisition step;
After the printing executed after the execution of the second switching step is interrupted , the use of the ink is resumed when resuming printing by discharging the specific ink onto the medium without passing through the second filling state. When the accumulated usage of the specific ink acquired in the amount acquisition step is less than a predetermined amount, a flow path cleaning step for discharging to discard the specific ink in a predetermined procedure;
An ink flow path cleaning control method in a printing apparatus.

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