Liquid dispensing device

Abstract

To provide means that can start discharging liquid quickly, when the liquid is newly supplied thereto.SOLUTION: In a printer 10, a plurality of nozzles 33 included in a head 32 form first-fourth nozzle rows K1-K4. A first sensor 41 and a second sensor 42 output high-level signals in accordance with the fact that a liquid level of ink stored in a sub tank 35 is upper than positions of the sensors and output low-level signals in accordance with the fact that the liquid level is less than the positions of the sensors. A control part 60 executes exhaust-purge of the first nozzle row K1 (S28), in accordance with the fact that the high-level signals are received after the low-level signals are received from the first sensor 41 (S25:Yes), and then executes exhaust-purge of the second-fourth nozzle rows K2-K4 (S43-S46), in accordance with the fact that the high-level signals are received from the second sensor 42 (S29:Yes), and then executes processing for ejecting ink (S13).SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection apparatus including a head including a plurality of nozzle rows. [Background Art]

[0002] There is known a printer that is capable of mounting a cartridge storing ink, and includes a tank that stores ink supplied from the mounted cartridge, and a head including a plurality of nozzles that eject the ink supplied from the tank. In such a printer, when a new cartridge is mounted in the tank, ink is supplied from the cartridge to the tank. When the amount of ink stored in the tank reaches or exceeds a predetermined level, the printer introduces ink into the head.

[0003] Patent Literature 1 discloses an image recording apparatus including a first sensor that detects whether an ink liquid level is higher than a first position, and a second sensor that detects whether the ink liquid level is higher than a second position located above the first position. This image recording apparatus notifies that the remaining amount of ink is low when the ink liquid level becomes lower than the first position after becoming lower than the second position, and cancels the notification when the ink liquid level becomes higher than the first position after a cartridge is mounted. [Prior Art Documents] [Patent Literature]

[0004] [Patent Literature 1] Japanese Unexamined Patent Publication No. 2020-163684 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] When a print head contains multiple nozzle rows, conventional printers might introduce ink to the head only after a sufficient amount of ink for all nozzle rows has been stored in the tanks. However, in this configuration, it takes time for the amount of ink stored in the tanks to reach the required level, resulting in a longer time between the cartridge being installed and the start of ink ejection.

[0006] This invention has been made in view of the above circumstances, and its object is to provide a means for initiating the discharge of liquid early when a new liquid is supplied. [Means for solving the problem]

[0007] (1) The liquid dispensing device of the present invention comprises a tank for storing liquid, a head including a plurality of nozzles for dispensing liquid supplied from the tank, a first sensor that outputs a first signal when the liquid level of a cartridge supplying liquid to the tank or the liquid stored in the tank is at or above a first position, and outputs a second signal when the liquid level is below the first position, and a control unit. The plurality of nozzles are arranged in a first direction to form a plurality of nozzle rows. The control unit, after receiving the second signal from the first sensor and in response to receiving the first signal, performs a first maintenance process to perform maintenance on some of the nozzle rows included in the head, and after performing the first maintenance process, performs a second maintenance process to perform maintenance on the remaining nozzle rows included in the head when predetermined conditions are met, and after performing the first maintenance process and the second maintenance process, performs a dispensing process to discharge liquid from the plurality of nozzles onto a sheet.

[0008] By performing maintenance processing on some nozzle rows in advance when the liquid level reaches a first position, and then performing maintenance processing on the remaining nozzle rows when predetermined conditions are met, maintenance processing can be started early when new liquid is supplied, and liquid discharge can be started early.

[0009] (2) Preferably, each of the plurality of nozzle rows has an exhaust port, and the control unit performs a suction purge to suck the nozzles in the nozzle row and an exhaust purge to suck the exhaust ports of the nozzle row as maintenance processing for the head, and the control unit may perform at least one of the suction purge and the exhaust purge on some of the nozzle rows in the first maintenance processing.

[0010] (3) Preferably, the liquid dispensing device further comprises a second sensor that outputs a third signal when the liquid level is at or above a second position higher than the first position, and outputs a fourth signal when the liquid level is below the second position, and the control unit may perform the second maintenance process after performing the first maintenance process, in response to receiving the third signal from the second sensor.

[0011] (4) Preferably, the liquid dispensing device further comprises an alarm, and the control unit may activate the alarm after performing the first maintenance process if it does not receive the third signal from the second sensor.

[0012] (5) Preferably, after activating the alarm device, the control unit may not perform the first maintenance process in response to receiving the first signal from the first sensor, but may perform the second maintenance process in response to receiving the third signal from the second sensor.

[0013] (6) Preferably, the control unit performs a third maintenance process for all of the plurality of nozzle rows, and when the control unit performs the third maintenance process, it may perform the maintenance process with a first amount of liquid in response to receiving the third signal from the second sensor, and perform the maintenance process with a second amount of liquid which is less than the first amount, in response to receiving the fourth signal from the second sensor and the first signal from the first sensor, so that the third maintenance process can be performed with liquid supplied from the tank.

[0014] (7) Preferably, the control unit may perform the following processes: calculate a first consumption amount, which is the amount of liquid consumed after the signal received from the first sensor changes from the first signal to the second signal; calculate a second consumption amount, which is the amount of liquid consumed after the signal received from the second sensor changes from the third signal to the fourth signal; and calculate the cumulative liquid consumption amount based on the second consumption amount from the second sensor until the second signal is received from the first sensor, and based on the first consumption amount and a fixed value after the second signal is received from the first sensor.

[0015] (8) Preferably, the control unit may perform the second maintenance process after performing the first maintenance process, in response to a predetermined time having elapsed since receiving the first signal from the first sensor. [Effects of the Invention]

[0016] According to the present invention, when a new liquid is supplied, the dispensing of the liquid can be started early. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1 is an external perspective view of a printer 10 according to an embodiment of the present invention. [Figure 2] Figure 2 is a longitudinal cross-sectional view showing the internal structure of the printer 10. [Figure 3]Figure 3 is a diagram showing the movement range of the carriage 31. [Figure 4] Figure 4 is a block diagram of the printer 10. [Figure 5] Figure 5(A) is a diagram showing the arrangement of nozzles 33 in the head 32, Figure 5(B) is an enlarged view of an image printed in the high image quality mode, and Figure 5(C) is an enlarged view of an image printed in the high speed mode. [Figure 6] Figure 6 is a diagram showing the configuration of the maintenance unit 51. [Figure 7] Figure 7 is a flowchart of the main process. [Figure 8] Figure 8 is a flowchart of the initial introduction purge process. [Figure 9] Figure 9 is a flowchart of the purge process. [Figure 10] Figure 10 is a flowchart of the dot count process. DETAILED DESCRIPTION OF EMBODIMENTS

[0018] Hereinafter, embodiments of the present invention will be described. It goes without saying that the embodiments described below are merely examples of the present invention, and the embodiments of the present invention can be appropriately modified without changing the gist of the present invention. In the following description, a progression from the starting point to the end point of an arrow is expressed as an orientation, and a passage along the line connecting the starting point and the end point of the arrow is expressed as a direction. In addition, a vertical direction 7 is defined with reference to a state where the printer 10 is installed so as to be usable (the state shown in Fig. 1), a front-rear direction 8 is defined with the surface where the opening 13 of the printer 10 is formed as the front surface, and a left-right direction 9 is defined when the printer 10 is viewed from the front surface. The vertical direction 7, the front-rear direction 8, and the left-right direction 9 are orthogonal to each other.

[0019] [Overview of Printer 10] The printer 10 according to the present embodiment is an example of a liquid ejection device that ejects ink (an example of a liquid) onto a sheet by an inkjet printing method. The printer 10 is a monochrome printer that ejects black ink onto a sheet.

[0020] The printer 10 has a housing 11 that is roughly rectangular in shape. As shown in Figures 1 and 2, the inside of the housing 11 is located a feed tray 14, a feed roller 21, a transport roller 22, a carriage 31, a head 32 mounted on the carriage 31 and having multiple nozzles 33, a platen 23 facing the head 32, an ejection roller 24, an ejection tray 15, a sub-tank 35, a mounting case 36 into which a cartridge 37 can be installed, and a tube 34 that connects the cartridge 37 installed in the mounting case 36 and the head 32. The multiple nozzles 33 are arranged in the front-to-back direction 8 on the underside of the head 32.

[0021] The printer 10 drives the feed roller 21 and the transport roller 22 to transport the sheet supported on the feed tray 14 along the transport path (shown as a dashed line in Figure 2) to the position of the platen 23. Next, the printer 10 ejects ink supplied from the cartridge 37 mounted in the mounting case 36 via the sub-tank 35 and tube 34 from the nozzle 33 of the head 32. As a result, the ink lands on the sheet supported on the platen 23, and the image to be formed is printed on the sheet. The printer 10 drives the discharge roller 24 to discharge the sheet with the printed image into the discharge tray 15.

[0022] The carriage 31 is supported by two guide rails 48 and 49 that extend in the left-right direction 9, and moves back and forth in the left-right direction 9. While the carriage 31 moves in the left-right direction 9, the printer 10 ejects ink from the nozzles 33 of the head 32. This records an image on a portion of the sheet facing the head 32. Next, the printer 10 transports the sheet on the transport rollers 22 so that the next area to be recorded faces the head 32. By repeatedly performing these processes alternately, an image is recorded on the sheet.

[0023] As shown in Figure 1, the housing 11 has a cover 18 on its front surface 12 and at the rightmost end in the left-right direction 9. An opening (not shown) is formed at the location of the cover 18. The cover 18 is rotatable between a position that closes the opening (the position shown in Figure 1) and a position that opens the opening. A single mounting case 36 is located in the storage space inside the housing 11 that extends beyond the opening. A cartridge 37 containing black ink is mounted in the mounting case 36.

[0024] The cartridge 37 has an ink chamber 38 (see Figure 2) capable of storing ink. When the cartridge 37 is installed in the mounting case 36, the ink stored in the ink chamber 38 flows into the sub-tank 35 via an ink channel 39 that connects the ink chamber 38 and the sub-tank 35. The sub-tank 35 temporarily stores the incoming ink. The ink stored in the sub-tank 35 is supplied to the head 32 via a tube 34.

[0025] [Liquid level sensor and mounted sensor 43] As shown in Figure 2, a first sensor 41 and a second sensor 42 are located on the rear surface of the sub-tank 35. The second sensor 42 is located above the first sensor 41. The first sensor 41 includes a light-emitting element (not shown) and a light-receiving element (not shown) facing each other across the sub-tank 35. For example, the light-emitting element is located on the left side of the sub-tank 35, and the light-receiving element is located on the right side of the sub-tank 35. At least at the locations of the first sensor 41 and the second sensor 42, the sub-tank 35 is made of a light-transmitting material.

[0026] When the liquid level of the ink stored in the sub-tank 35 is below the position of the first sensor 41, the light emitted from the light-emitting element is incident on the photodetector. At this time, the first sensor 41 outputs, for example, a low-level signal. On the other hand, when the liquid level of the ink stored in the sub-tank 35 is above the position of the first sensor 41, the light emitted from the light-emitting element is scattered by the ink stored in the sub-tank 35, and the amount of light incident on the photodetector decreases. At this time, the first sensor 41 outputs, for example, a high-level signal. The second sensor 42 has the same configuration as the first sensor 41 and operates in the same manner as the first sensor 41.

[0027] The vertical position 7 of the first sensor 41 is an example of the first position. The high-level signal output from the first sensor 41 is an example of the first signal. The low-level signal output from the first sensor 41 is an example of the second signal. The vertical position 7 of the second sensor 42 is an example of the second position. The high-level signal output from the second sensor 42 is an example of the third signal. The low-level signal output from the second sensor 42 is an example of the fourth signal.

[0028] The first sensor 41 outputs a first signal when the liquid level of the ink stored in the sub-tank 35 is at or above a first position, and outputs a second signal when the liquid level is below the first position. The second sensor 42 outputs a third signal when the liquid level of the ink stored in the sub-tank 35 is at or above a second position, and outputs a fourth signal when the liquid level is below the second position. In the following description, the first sensor 41 and the second sensor 42 are referred to as ON when they are outputting a high-level signal and OFF when they are outputting a low-level signal.

[0029] The mounting sensor 43 is located above the cartridge 37 mounted in the mounting case 36. The mounting sensor 43 includes a light-emitting element (not shown) and a light-receiving element (not shown). A projection (not shown) for mounting detection is located on the upper surface of the cartridge 37. The projection is made of a material that does not transmit light. When the cartridge 37 is mounted in the mounting case 36, the projection is located between the light-emitting element and the light-receiving element of the mounting sensor 43.

[0030] When the cartridge 37 is not installed in the mounting case 36, the light emitted from the light-emitting element enters the photodetector. In this case, the mounting sensor 43 outputs a low-level signal. On the other hand, when the cartridge 37 is installed in the mounting case 36, the light emitted from the light-emitting element is blocked by the protrusion and does not enter the photodetector. In this case, the mounting sensor 43 outputs a high-level signal.

[0031] In the above explanation, the first sensor 41, the second sensor 42, and the mounted sensor 43 are assumed to be optical sensors, but the configuration of these sensors can be arbitrary. For example, the first sensor 41 and the second sensor 42 may be float-type sensors or electrode-type sensors.

[0032] [Carriage 31's movement range] As shown in Figure 3, the platen 23 has a long shape in the left-right direction 9 and is located below the carriage 31 in the up-down direction 7 (see Figure 2). The left end of the platen 23 is located near the left end of the guide rails 48 and 49 in the left-right direction 9. The right end of the platen 23 is located to the right of the center of the guide rails 48 and 49 in the left-right direction 9. The maintenance section 51 is located to the right of the platen 23 in the left-right direction 9.

[0033] The maintenance unit 51 includes four nozzle caps 52 and an exhaust port cap 53. While the printer 10 is printing, the carriage 31 moves left and right within the range of the platen 23. When the printer 10 is not printing, the carriage 31 is positioned so that the head 32 faces the nozzle caps 52 and the exhaust port cap 53 (hereinafter referred to as the standby position).

[0034] [Control Unit 60] Inside the enclosure 11 is the control unit 60 shown in Figure 4. The control unit 60 includes a CPU 61, ROM 62, RAM 63, EEPROM 64, and ASIC 65. ROM 62 stores programs and other information for the CPU 61 to execute various processes. RAM 63 is used as a temporary storage area for data and signals used by the CPU 61 when executing programs, or as a working area for data processing. EEPROM 64 stores information that should be retained even after the power is turned off.

[0035] The control unit 60 controls the feed roller 21, transport roller 22, discharge roller 24, carriage 31, and head 32. The control unit 60 rotates the feed roller 21, transport roller 22, and discharge roller 24 by driving a motor (not shown) via the ASIC 65. The control unit 60 moves the carriage 31 in the left-right direction 9 by driving a motor (not shown) via the ASIC 65. The control unit 60 ejects ink from the nozzle 33 of the head 32 by outputting a drive signal to the drive element (not shown) of the head 32 via the ASIC 65. The ASIC 65 outputs a drive signal corresponding to the amount of ink to be ejected from the nozzle 33.

[0036] The control unit 60 receives signals output from the first sensor 41, the second sensor 42, and the mounting sensor 43 via the ASIC 65. Based on the signal received from the first sensor 41, the control unit 60 detects whether the liquid level of the ink stored in the sub-tank 35 is above the position of the first sensor 41. Based on the signal received from the second sensor 42, the control unit 60 detects whether the liquid level of the ink stored in the sub-tank 35 is above the position of the second sensor 42. Based on the signal received from the mounting sensor 43, the control unit 60 detects whether the cartridge 37 is mounted in the mounting case 36.

[0037] The control unit 60 controls each part of the maintenance unit 51. The control unit 60 moves the nozzle cap 52 and exhaust port cap 53 together in the vertical direction 7 by driving a motor (not shown) through the ASIC 65. The control unit 60 moves the lifting member 54 in the vertical direction 7 by driving a motor (not shown) through the ASIC 65. The control unit 60 switches the state of the flow path switching unit 56 by outputting a control signal through the ASIC 65. The control unit 60 operates the pump 57 by outputting a control signal through the ASIC 65. The configuration of the maintenance unit 51 will be described later.

[0038] The ASIC65 is connected to a display unit 16 and an operation panel 17. The display unit 16 is, for example, a liquid crystal display or an organic EL display. The display unit 16 displays, for example, the status of the printer 10 on its screen. The operation panel 17 outputs operation signals to the control unit 60 in response to user operations. The operation panel 17 may have, for example, push buttons or a touch sensor superimposed on the display unit 16. The display unit 16 is an example of an alarm device.

[0039] [Arrangement of nozzle 33] Figure 5(A) shows the arrangement of the nozzles 33 on the head 32. In Figure 5(A), the horizontal direction is the direction of movement of the carriage 31, and the vertical direction is the direction of sheet transport. In the following description, the former will be referred to as the main scanning direction, and the latter as the sub-scanning direction. In this embodiment, the main scanning direction and the sub-scanning direction are orthogonal. The white circles shown in Figure 5(A) indicate the position of the nozzles 33 when the head 32 is viewed from above.

[0040] The head 32 includes a first nozzle row K1, a second nozzle row K2, a third nozzle row K3, and a fourth nozzle row K4. The first nozzle row K1 consists of multiple nozzles 33 arranged at a pitch P in the sub-scanning direction (an example of the first direction). The second to fourth nozzle rows K2 to K4 each consist of the same number of nozzles 33 as the first nozzle row K1, arranged at the same pitch P in the sub-scanning direction. In this embodiment, the pitch P is 1 / 300 inch. The second nozzle row K2 is located to the right of the first nozzle row K1. The third nozzle row K3 is located to the right of the second nozzle row K2. The fourth nozzle row K4 is located to the right of the third nozzle row K3. The distance between two nozzle rows in the main scanning direction is arbitrary.

[0041] The sub-scanning position of nozzle 33 in the second nozzle row K2 is shifted by 1 / 4 of the pitch P (i.e., 1 / 1200 of an inch) from the sub-scanning position of nozzle 33 in the first nozzle row K1. The sub-scanning position of nozzle 33 in the third nozzle row K3 is shifted by 1 / 2 of the pitch P from the sub-scanning position of nozzle 33 in the first nozzle row K1. The sub-scanning position of nozzle 33 in the fourth nozzle row K4 is shifted by 3 / 4 of the pitch P from the sub-scanning position of nozzle 33 in the first nozzle row K1.

[0042] The nozzles 33 in the first to fourth nozzle rows K1 to K4 are divided into groups of four in the order of their arrangement in the sub-scanning direction, and the four nozzles 33 within each group correspond to one another. For example, the nozzles 33 located in the first to fourth rows correspond to one another, and the nozzles 33 located in the fifth to eighth rows correspond to one another.

[0043] Although Figure 5(A) shows four nozzles 33 for each nozzle row, the actual number of nozzles 33 within each nozzle row is more than four. Also, while the head 32 is shown to contain four nozzle rows, the head 32 may contain two, three, or five or more nozzle rows.

[0044] In addition to forming multiple nozzles 33 on the head 32 such that their positions in the sub-scanning direction differ for each nozzle row, there is another method for arranging multiple nozzles 33 in the configuration shown in Figure 5(A): forming multiple nozzles 33 on the head 32 such that their positions in the sub-scanning direction are the same across the nozzle rows, and then tilting the head 32 by a small angle (rotating it by a small angle in the horizontal plane) and attaching it to the carriage 31.

[0045] [Printer 10 operating modes] The printer 10 operates in either high-quality mode or high-speed mode. Figure 5(B) shows a magnified image printed in high-quality mode. Figure 5(C) shows a magnified image printed in high-speed mode. The black circles shown in Figures 5(B) and 5(C) represent dots made by ink ejected from the nozzles 33.

[0046] In high-quality mode (Figure 5(B)), the carriage 31 moves at a predetermined speed in the main scanning direction, and ink is ejected from nozzles 33 in the first to fourth nozzle rows K1 to K4 each time the carriage 31 moves 1 / 600 of an inch in the main scanning direction. In this case, one line of the image is formed by a group of dots made by the ink ejected from one nozzle 33. Therefore, in high-quality mode, an image with a resolution of 600 dpi in the main scanning direction and a resolution of 1200 dpi in the sub-scanning direction is formed on the sheet.

[0047] In high-speed mode (Figure 5(C)), the carriage 31 moves at a faster speed in the main scanning direction than in high-quality mode, and ink is ejected from the nozzles 33 in the first to fourth nozzle rows K1 to K4 each time the carriage 31 moves 1 / 300 of an inch in the main scanning direction. However, the ink ejection timing from the nozzles 33 in the second nozzle row K2 and the fourth nozzle row K4 is delayed so that the landing position of the ink ejected from these nozzles 33 is shifted by 1 / 600 of an inch in the main scanning direction of the carriage 31 relative to the landing position of the ink ejected from the nozzles 33 in the first nozzle row K1 and the third nozzle row K3.

[0048] In this case, one line of the image is formed by a group of dots made from ink ejected from one nozzle 33 and a group of dots made from ink ejected from an adjacent nozzle 33. Specifically, odd-numbered lines of the image are formed by a group of dots made from ink ejected from a nozzle 33 in the first nozzle row K1 and a group of dots made from ink ejected from a nozzle 33 in the second nozzle row K2. Even-numbered lines of the image are formed by a group of dots made from ink ejected from a nozzle 33 in the third nozzle row K3 and a group of dots made from ink ejected from a nozzle 33 in the fourth nozzle row K4. The spacing between dots in the main scanning direction is 1 / 600 of an inch. Therefore, in high-speed mode, an image with a resolution of 600 dpi in the main scanning direction and a resolution of 600 dpi in the sub-scanning direction is printed.

[0049] [Maintenance Department 51] Figure 6 shows the configuration of the head 32, specifically the part corresponding to one nozzle row, and the maintenance section 51. On the underside of the head 32 are the first to fourth nozzle rows K1 to K4, each containing multiple nozzles 33 arranged in the sub-scanning direction, and four exhaust ports 71, each corresponding to a nozzle row. Figure 6 shows one of these nozzle rows and the exhaust port 71 corresponding to that nozzle row.

[0050] When the carriage 31 is in the standby position, the nozzle cap 52 faces the nozzle row, and the exhaust port cap 53 faces the exhaust port 71. Inside the head 32, an ink flow path 72 is formed, connecting the ink inlet 73 and the nozzles 33. The exhaust port 71 is connected to the upper part of the ink flow path 72 via a flow path 74.

[0051] The flow path 74 has an enlarged diameter section 75. A spring 76 and a valve body 77 are located in the internal space of the enlarged diameter section 75. The valve body 77 has a main body section 78 and a projection section 79. The main body section 78 has an outer diameter approximately equal to the inner diameter of the enlarged diameter section 75 and is located within the enlarged diameter section 75. The projection section 79 has an outer diameter smaller than the inner diameter of the enlarged diameter section 75 and protrudes downward from the enlarged diameter section 75 toward the exhaust port 71. The spring 76 is located above the valve body 77 and biases the valve body 77 downward. In the normal state, the main body section 78 is pressed against the bottom surface of the enlarged diameter section 75 by the action of the spring 76, and the exhaust port 71 is closed. Below the exhaust port cap 53 is a lifting member 54 having an upwardly protruding contact section 55.

[0052] The nozzle cap 52 and exhaust port cap 53 move up and down between a position in contact with the lower surface of the head 32 (hereinafter referred to as the covering position) and a position spaced apart from the lower surface of the head 32 (hereinafter referred to as the spaced position), according to control from the control unit 60. When the carriage 31 is in the standby position, the nozzle cap 52 and exhaust port cap 53 are in the covering position. At this time, the nozzle cap 52 contacts the periphery of the nozzle row to cover the nozzle row, and the exhaust port cap 53 contacts the periphery of the exhaust port 71 to cover the exhaust port 71. When the carriage 31 is in a position other than the standby position, the nozzle cap 52 and exhaust port cap 53 are in the spaced position. At this time, the nozzle cap 52 is located spaced downward from the periphery of the nozzle row, and the exhaust port cap 53 is located spaced downward from the periphery of the exhaust port 71.

[0053] The bottom surface of the nozzle cap 52 has an outlet 81. The internal space of the nozzle cap 52 is connected to a terminal of the flow path switching unit 56 via the outlet 81. The bottom surface of the exhaust port cap 53 has an outlet 82. The internal space of the exhaust port cap 53 is connected to another terminal of the flow path switching unit 56 via the outlet 82. Although not shown in Figure 6, another terminal of the flow path switching unit 56 is connected to the internal space of a nozzle cap 52 corresponding to another nozzle row. Another terminal of the flow path switching unit 56 is connected to one end of the pump 57. The flow path switching unit 56 connects one of the internal spaces of the four nozzle caps 52 and the internal space of the exhaust port cap 53 to one end of the pump 57. The other end of the pump 57 is connected to the waste liquid tank 58. The waste liquid tank 58 stores the ink discharged from the head 32 by the purging process.

[0054] The maintenance unit 51 has four lifting members 54 corresponding to the four exhaust ports 71. The lifting members 54 move vertically 7 between a relatively high contact position and a relatively low non-contact position, independently of the nozzle cap 52, exhaust port cap 53 and the other lifting members 54, according to control from the control unit 60. When the exhaust port cap 53 is in the covering position and the lifting member 54 is in the contact position, the upper surface of the contact portion 55 contacts the bottom surface of the protruding portion 79. At this time, the valve body 77 moves upward against the restoring force of the spring 76 and separates from the bottom surface of the enlarged diameter portion 75. As a result, the exhaust port 71 is in an open state.

[0055] When the nozzle cap 52 and exhaust port cap 53 are in the covered position and the lifting member 54 is in the non-contact position, the exhaust port 71 is closed. In this state, the internal space of the nozzle cap 52 and the pump 57 are connected by the flow path switching unit 56 and the pump 57 is driven, thereby applying suction pressure from the nozzle 33 to the ink flow path 72. As a result, the ink and gas in the ink flow path 72 are discharged from the nozzle 33. The ink discharged from the nozzle 33 is stored in the waste liquid tank 58. In this way, a suction purge is performed to draw in the nozzles 33 in the nozzle row.

[0056] When the nozzle cap 52 and exhaust port cap 53 are in the covering position and the lifting member 54 is in the contact position, the exhaust port 71 is open. In this state, the internal space of the exhaust port cap 53 and the pump 57 are connected by the flow path switching unit 56 and the pump 57 is driven, thereby applying suction pressure from the exhaust port 71 to the ink flow path 72. As a result, the ink and gas in the ink flow path 72 are discharged from the exhaust port 71. Mainly gas is discharged from the exhaust port 71. In this way, an exhaust purge is performed by suctioning the exhaust port 71 of the nozzle row.

[0057] The control unit 60 controls the maintenance unit 51 to perform suction purging and exhaust purging as maintenance processing for the head 32 at different timings. The control unit 60 controls the lifting member 54 and the flow path switching unit 56 to perform either suction purging or exhaust purging for one or more nozzle rows selected from the first to fourth nozzle rows K1 to K4.

[0058] [Main process] The control unit 60 executes the main process shown in Figure 7 by having the CPU 61 execute a program stored in the RAM 63. If conditions are met during the execution of the main process, the control unit 60 executes the initial introduction purge process (Figure 8), the purge process (Figure 9), and the dot count process (Figure 10).

[0059] Referring to Figure 7, the main processing performed by the control unit 60 is explained. As shown in Figure 7, at the beginning of the main processing, the control unit 60 determines whether or not to perform printing (S11). In S11, the control unit 60 determines to perform printing, for example, if it receives a print command from the user. In response to its determination to perform printing (S11: Yes), the control unit 60 proceeds to S12. In this case, the control unit 60 determines whether or not printing is complete (S12). In response to its determination that printing is not complete (S12: No), the control unit 60 proceeds to S13. In this case, the control unit 60 performs the printing process (S13) and the dot counting process (S14), and then proceeds to S12. In S13, the control unit 60 ejects ink supplied from the sub-tank 35 onto the sheet from multiple nozzles 33. In response to its determination in S12 that printing is complete (S12: Yes), the control unit 60 proceeds to S11.

[0060] If the control unit 60 decides in S11 not to perform printing (S11: No), it proceeds to S15. In this case, the control unit 60 decides whether or not to perform an initial setup purge (S15). In S15, the control unit 60 decides to perform an initial setup purge, for example, if it receives an initial setup purge instruction from the user. If the control unit 60 decides to perform an initial setup purge (S15: Yes), it proceeds to S16. In this case, the control unit 60 performs the initial setup purge process (S16) and proceeds to S11.

[0061] If the control unit 60 determines in S15 that it will not perform the initial introduction purge (S15: No), it proceeds to S17. In this case, the control unit 60 determines whether or not to perform the purge process (S17). In the purge process, at least one of suction purging and exhaust purging is performed for all nozzle rows (first to fourth nozzle rows K1 to K4) included in the head 32. In S17, the control unit 60 determines to perform the purge process, for example, when it receives a purge instruction from the user or when a predetermined time has elapsed since the last execution of a purge instruction. If the control unit 60 determines to perform the purge process (S17: Yes), it proceeds to S18. In this case, the control unit 60 performs the purge process (S18) and proceeds to S11. If the control unit 60 determines in S17 that it will not perform the purge process (S17: No), it proceeds to S19. In this case, the control unit 60 performs other processes (printing, initial introduction purging, and processes other than purging) (S19) and proceeds to S11.

[0062] [Initial setup purging process] Referring to Figure 8, the initial introduction purge process performed by the control unit 60 is explained. In the initial introduction purge process, the time elapsed since the cartridge 37 was installed in the mounting case 36 is measured, and an error flag is used. The initial value of the error flag is OFF. The error flag is set to ON when, during a predetermined time elapsed since the cartridge 37 was installed, the first sensor 41 turns ON, but the second sensor 42 does not turn ON. When the error flag is ON, the exhaust purge of the first nozzle row K1 has been performed.

[0063] As shown in Figure 8, at the beginning of the initial introduction purge process, the control unit 60 determines whether or not the cartridge 37 is installed in the mounting case 36 based on the signal received from the mounting sensor 43 (S21). If the control unit 60 determines that the cartridge 37 is not installed (S21: No), it proceeds to S22. In this case, the control unit 60 displays on the display unit 16 that the cartridge should be installed (S22), and proceeds to S21.

[0064] In response to determining in S21 that the cartridge 37 is installed (S21: Yes), the control unit 60 proceeds to S23. In this case, the control unit 60 starts timing (S23). Next, the control unit 60 determines whether the error flag is ON or OFF (S24). The error flag is set to ON if the exhaust purge of the first nozzle row K1 has been performed, and OFF if it has not been performed.

[0065] The control unit 60 determines that the error flag is not ON (meaning that the exhaust purging of the first nozzle row K1 has not been performed) (S24: No), and proceeds to S25. In this case, the control unit 60 determines whether the first sensor 41 is ON or OFF (S25). The first sensor 41 is determined to be ON when the liquid level of the ink stored in the sub-tank 35 is above the position of the first sensor 41, and OFF when the liquid level is below the position of the first sensor 41.

[0066] If the control unit 60 determines that the first sensor 41 is not ON (liquid level is below the position of the first sensor 41) (S25: No), it proceeds to S26. In this case, the control unit 60 displays "Waiting for inflow" on the display unit 16 (S26). Next, the control unit 60 determines whether a predetermined time has elapsed (S27). The predetermined time in S27 is the time it is predicted that enough ink to perform exhaust purging of the first nozzle row K1 will be supplied to the sub-tank 35. If the control unit 60 determines that the predetermined time has not elapsed (S27: No), it proceeds to S25. From S25 to S27, the control unit 60 waits until the liquid level of the ink stored in the sub-tank 35 is above the position of the first sensor 41.

[0067] In response to determining in S25 that the first sensor 41 is ON (liquid level is above the position of the first sensor 41) (S25: Yes), the control unit 60 proceeds to S28. In this case, the control unit 60 performs an exhaust purge of the first nozzle row K1 (S28). The control unit 60 performs an exhaust purge of the first nozzle row K1 when the liquid level of the ink stored in the sub-tank 35 is above the position of the first sensor 41.

[0068] Next, the control unit 60 determines whether the second sensor 42 is ON or OFF (S29). The second sensor 42 is determined to be ON when the liquid level of the ink stored in the sub-tank 35 is above the position of the second sensor 42, and OFF when it is below the position of the second sensor 42.

[0069] If the control unit 60 determines that the second sensor 42 is not ON (liquid level is below the position of the second sensor 42) (S29: No), it proceeds to S31. In this case, the control unit 60 displays "Waiting for inflow" on the display unit 16 (S31). Next, the control unit 60 determines whether a predetermined time has elapsed (S32). The predetermined time in S32 is the time it is predicted that enough ink to perform the purging in S43 to S46 will be supplied to the sub-tank 35, and is equal to or greater than the predetermined time in S27. If the control unit 60 determines that the predetermined time has not elapsed (S32: No), it proceeds to S29. In S29, S31, and S32, the control unit 60 waits until the liquid level of the ink stored in the sub-tank 35 is equal to or greater than the position of the second sensor 42.

[0070] In response to determining in S29 that the second sensor 42 is ON (liquid level is above the position of the second sensor 42) (S29: Yes), the control unit 60 proceeds to S41. In this case, the control unit 60 terminates the timing (S41) and sets the error flag to OFF (S42). Next, the control unit 60 sequentially performs exhaust purging of the second to fourth nozzle rows K2 to K4 (S43), suction purging of the first nozzle row K1 (S44), and suction purging of the second to fourth nozzle rows K2 to K4 (S45).

[0071] Next, the control unit 60 performs the remaining purging process (S46). In S46, the control unit 60 repeatedly performs exhaust purging and suction purging of the first to fourth nozzle rows K1 to K4 multiple times (for example, three times). At this time, the control unit 60 detects the liquid level of the ink stored in the sub-tank 35 based on signals received from the first sensor 41 and the second sensor 42, and after confirming that a sufficient amount of ink is stored in the sub-tank 35, it performs each purging process. Next, the control unit 60 performs dot counting (S47) and finishes the initial introduction purging process.

[0072] In response to determining in S24 that the error flag is ON (meaning that the exhaust purging of the first nozzle row K1 has been performed) (S24: Yes), the control unit 60 proceeds to S29 without executing S25 to S28. If the exhaust purging of the first nozzle row K1 has already been performed, the control unit 60 waits without performing the exhaust purging of the first nozzle row K1 until the liquid level of the ink stored in the sub-tank 35 reaches or exceeds the position of the second sensor 42.

[0073] In S27, the control unit 60 determines that a predetermined time has elapsed (S27: Yes) and proceeds to S34. In this case, the control unit 60 displays on the display unit 16 that an ink inflow error has occurred (S34) and terminates the initial introduction purge process.

[0074] In S32, the control unit 60 determines that a predetermined time has elapsed (S32: Yes) and proceeds to S33. In this case, the control unit 60 sets the error flag to ON (S33), displays on the display unit 16 that an ink inflow error has occurred (S34), and terminates the initial introduction purge process.

[0075] In the initial introduction purge process, S28 is an example of a first maintenance process that performs maintenance on some of the nozzle rows included in the head 32. The second sensor 42 being ON is an example of a predetermined condition. S43 to S46 are an example of a second maintenance process that performs maintenance on the remaining nozzle rows included in the head 32. In the main process, S13 is an example of a discharge process that discharges liquid from multiple nozzles 33 onto the sheet after the first and second maintenance processes have been performed.

[0076] When the control unit 60 first reaches S35, the ink level in the sub-tank 35 is low, and the first sensor 41 is OFF. Subsequently, ink is supplied from the cartridge 37 to the sub-tank 35, and when the ink level in the sub-tank 35 rises above the position of the first sensor 41, the first sensor 41 turns ON. In response to the change in the first sensor 41 from OFF to ON (in response to receiving the first signal after receiving the second signal from the first sensor 41), the control unit 60 executes S28 (first maintenance process).

[0077] After executing S28, the control unit 60 executes S43 to S46 (second maintenance processing) in response to determining in S29 that the second sensor 42 is ON (in response to receiving the third signal from the second sensor 42). After executing S28, the control unit 60 activates the display unit 16 as an alarm in S34 in response to determining that the second sensor 42 is not ON (in response to not receiving the third signal from the second sensor 42). After activating the alarm in S34, the control unit 60 does not execute S28 (first maintenance processing) even if the first sensor 41 is ON (even if the first signal is received from the first sensor 41), and instead executes S43 to S46 (second maintenance processing) in response to determining in S29 that the second sensor 42 is ON (in response to receiving the third signal from the second sensor 42).

[0078] [Purge process] Referring to Figure 9, the purge process performed by the control unit 60 is explained. In the purge process, the rank R of the purge to be performed and the amount of ink V required for the purge are obtained. The purge rank R can be, for example, 1, 2, 3, 4, 5, or "none". The higher the purge rank R, the greater the amount of ink V required. A purge rank R of "none" indicates that the type of purge is fixed and the purge rank R cannot be changed.

[0079] In the following explanation, V1 is the amount of ink stored in the sub-tank 35 when the ink level is at the position of the first sensor 41, V2 is the amount of ink stored in the sub-tank 35 when the ink level is at the position of the second sensor 42, C1 is the amount of ink consumed after the signal output from the first sensor 41 changes from a high-level signal to a low-level signal (after the liquid level reaches the position of the first sensor 41), and C2 is the amount of ink consumed after the signal output from the second sensor 42 changes from a high-level signal to a low-level signal (after the liquid level reaches the position of the second sensor 42).

[0080] As shown in Figure 9, the control unit 60 obtains the rank R of the purge to be executed at the beginning of the purge process (S51). In S51, the control unit 60 may obtain, for example, a rank set by the user as the rank R of the purge, or it may obtain the rank R of the purge based on the percentage and number of abnormal nozzles obtained by nozzle ejection detection. Next, the control unit 60 obtains the amount of ink V required to execute the purge (S52). For example, the ROM 62 stores a table that associates the rank R of the purge with the required amount V, and the CPU 61 may read the required amount V corresponding to the rank R obtained in S51 from the table stored in the ROM 62.

[0081] Next, the control unit 60 determines whether the second sensor 42 is ON or OFF (whether the liquid level is above or above the position of the second sensor 42) (S53). When the second sensor 42 is ON, a sufficient amount of ink for purging is stored in the sub-tank 35. In response to the control unit 60 determining that the second sensor 42 is ON (S53: Yes), the process proceeds to S54. In this case, the control unit 60 performs purging of rank R (S54) and dot counting (S55), and then terminates the purging process.

[0082] In response to the control unit 60 determining in S53 that the second sensor 42 is not ON (liquid level is below the position of the second sensor 42) (S53: No), the control unit 60 proceeds to S56. In this case, the control unit 60 determines whether the first sensor 41 is ON or not (whether the liquid level is at or above the position of the first sensor 41) (S56).

[0083] The control unit 60 determines that the first sensor 41 is ON (S56: Yes) and proceeds to S57. In this case, the control unit 60 determines whether the required ink amount V is less than or equal to V1 (the amount of ink at the time the first sensor 41 changes from ON to OFF) (S57). If the required ink amount V is less than or equal to V1, the amount of ink necessary to perform the purging process is stored in the sub-tank 35. The control unit 60 determines that the ink amount V is less than or equal to V1 (S57: Yes) and proceeds to S54. In this case, the control unit 60 performs the purging of rank R (S54) and the dot counting process (S55), and then terminates the purging process.

[0084] In S57, the control unit 60 determines that the ink amount V is not less than or equal to V1 (S57: No), and proceeds to S61. In this case, the control unit 60 determines whether the ink amount V is less than (V2-C2) (S61). (V2-C2) is the amount of ink stored in the sub-tank 35 at this point. If the required ink amount V is less than (V2-C2), then the amount of ink required to perform the purging process is stored in the sub-tank 35. In S61, the control unit 60 determines that the required ink amount V is less than (V2-C2), and proceeds to S54 (S61: Yes). In this case, the control unit 60 performs the purging of rank R (S54) and the dot counting process (S55), and then terminates the purging process.

[0085] In S61, the control unit 60 determines that the required ink amount V is not less than (V2-C2) (S61: No) and proceeds to S62. In this case, the control unit 60 determines whether the purge rank R is "1" or "none" (S62). If the purge rank R is "1" or "none", the purge rank R cannot be lowered. In S62, the control unit 60 determines that the purge rank R is "1" or "none" (S62: Yes) and proceeds to S64. In this case, the control unit 60 displays on the display unit 16 that it refuses to perform the purge (S64) and terminates the purge process.

[0086] In S62, the control unit 60 determines that the purge rank R is not "1" or "none" (S62: No), and proceeds to S63. In this case, the control unit 60 lowers the purge rank (S63) and proceeds to S57. In S63, the control unit 60 determines that V is the amount of ink required to perform the purge of the lowered rank R.

[0087] In response to the control unit 60 determining in S56 that the first sensor 41 is not ON (liquid level is below the position of the first sensor 41) (S56: No), the process proceeds to S65. In this case, the control unit 60 determines whether the required ink amount V is less than (V1-C1) (S62). (V1-C1) is the amount of ink stored in the sub-tank 35 at this point. If the required ink amount V is less than (V1-C1), then the amount of ink required to perform the purging process is stored in the sub-tank 35. In response to the control unit 60 determining that the required ink amount V is less than (V1-C1) (S65: Yes), the process proceeds to S54. In this case, the control unit 60 performs the purging of rank R (S54) and the dot counting process (S55), and then terminates the purging process.

[0088] In S65, the control unit 60 determines that the required ink amount V is not less than (V1-C1) (S65: No) and proceeds to S66. In this case, the control unit 60 determines whether the purge rank is "1" or "none" (S66). In this case, the control unit 60 determines that the purge rank is "1" or "none" (S66: Yes) and proceeds to S64. In this case, the control unit 60 displays on the display unit 16 that it refuses to perform the purge (S64) and terminates the purge process.

[0089] If the control unit 60 determines in S66 that the purge rank R is not "1" or "none" (S66: No), it proceeds to S67. In this case, the control unit 60 lowers the purge rank (S67) and proceeds to S65. In S67, the control unit 60 determines that V is the amount of ink required to perform the purge of the lowered rank R.

[0090] The purging process is an example of a third maintenance process that performs maintenance on all of the multiple nozzle rows contained in the head 32. S54, when Yes is determined in S53, is an example of a maintenance process performed with a first volume of liquid. S54, which is performed after S63, is an example of a maintenance process performed with a second volume of liquid, which is less than the first volume.

[0091] When the control unit 60 performs a third maintenance process that performs maintenance on all of the multiple nozzle rows, it performs the maintenance process with a first amount of ink in response to receiving a third signal from the second sensor 42, and performs the maintenance process with a second amount of ink, which is less than the first amount, in response to receiving a fourth signal from the second sensor 42 and a first signal from the first sensor 41, so that the third maintenance process can be performed with ink supplied from the sub-tank 35.

[0092] [Dot counting process] Referring to Figure 10, the dot counting process performed by the control unit 60 is explained. In the dot counting process, three ink consumption amounts (dot count C0, sensor dot count C1, and sensor dot count C2) are calculated by accumulating and adding up the ink consumption amounts.

[0093] The dot count C0 is the amount of ink consumed after the initial state in which a new cartridge 37 is installed in the mounting case 36. The dot count C0 is reset to 0 at a predetermined timing and calculated by accumulating the ink consumption thereafter. The sensor dot count C1 is the same as C1 explained in the purging process and is the amount of ink consumed after the signal received from the first sensor 41 changes from a high-level signal to a low-level signal. The sensor dot count C1 is reset to 0 when the signal received from the first sensor 41 changes from a high-level signal to a low-level signal and calculated by accumulating the ink consumption thereafter. The sensor dot count C2 is the same as C2 explained in the purging process and is the amount of ink consumed after the signal received from the second sensor 42 changes from a high-level signal to a low-level signal. The sensor dot count C2 is reset to 0 when the signal received from the second sensor 42 changes from a high-level signal to a low-level signal and calculated by accumulating the ink consumption thereafter.

[0094] As shown in Figure 10, the control unit 60 sets the current ink consumption amount as X at the beginning of the dot counting process (S71). The current ink consumption amount X is the amount of ink consumed in the printing process (S13) or purging process (S28 and S43-S46, or S54) performed before the dot counting process.

[0095] Next, the control unit 60 determines whether the second sensor 42 is ON or not (S72). If the control unit 60 determines that the second sensor 42 is ON (S72: Yes), it proceeds to S81. If the control unit 60 determines that the second sensor 42 is not ON (S72: No), it proceeds to S73. In this case, the control unit 60 determines whether the first sensor 41 is ON or not (S73). If the control unit 60 determines that the first sensor 41 is ON (S73: Yes), it proceeds to S83. If the control unit 60 determines that the first sensor 41 is not ON (S73: No), it proceeds to S86.

[0096] When the ink level in the sub-tank 35 is above the position of the second sensor 42, the control unit 60 reaches S81. In this case, the control unit 60 adds the ink consumption amount X to the dot count C0 (S81). Next, the control unit 60 sets the dot count C0 to the cumulative ink consumption amount (S82).

[0097] The control unit 60 reaches S83 when the ink level in the sub-tank 35 is above the position of the first sensor 41 and below the position of the second sensor 42. In this case, the control unit 60 adds the ink consumption amount X to the dot count C0 (S83) and also adds the ink consumption amount X to the sensor dot count C2 (S84). Next, the control unit 60 calculates the cumulative ink consumption amount based on the sensor dot count C2 (S85). For example, the control unit 60 stores the dot count C0 at the time the second sensor 42 changes from ON to OFF in the RAM 63, and in S85, the sum of the dot count C0 stored in the RAM 63 and the sensor dot count C2 is taken as the cumulative ink consumption amount.

[0098] The control unit 60 reaches S86 when the ink level in the sub-tank 35 is below the position of the first sensor 41. In this case, the control unit 60 adds the ink consumption amount X to the dot count C0 (S86), adds the ink consumption amount X to the sensor dot count C2 (S87), and further adds the ink consumption amount X to the sensor dot count C1 (S88). Next, the control unit 60 calculates the ink consumption amount based on the sensor dot count C1 and (V2-V1) (S89). (V2-V1) is the difference between the amount of ink V2 stored in the sub-tank 35 when the ink level is at the position of the second sensor 42 and the amount of ink V1 stored in the sub-tank 35 when the ink level is at the position of the first sensor 41, and is a fixed value. In S89, the control unit 60 uses the sum of the dot count C0, sensor dot count C1, and (V2-V1) stored in the RAM 63 at the time the second sensor 42 changes from ON to OFF as the cumulative ink consumption.

[0099] After executing S82, S85, and S89, the control unit 60 terminates the dot counting process. The cumulative ink consumption obtained in S82, S85, and S89 is used for various processes in the printer 10. For example, based on the cumulative ink consumption, the control unit 60 displays on the display unit 16 that the cartridge 37 should be replaced.

[0100] Sensor dot count C1 is an example of the first consumption. S88 is an example of the process for calculating the first consumption. Sensor dot count C2 is an example of the second consumption. S84 and S87 are examples of the process for calculating the second consumption. Cumulative ink consumption is an example of cumulative liquid consumption. S85 and S89 are examples of the process for calculating cumulative liquid consumption.

[0101] [Effects and Effects] As described above, the printer 10 according to this embodiment includes a sub-tank 35, a head 32 including a plurality of nozzles 33, a first sensor 41, and a control unit 60. The plurality of nozzles 33 are arranged in the sub-scanning direction to form a plurality of nozzle rows. The control unit 60 receives a low-level signal from the first sensor 41 and then, in response to receiving a high-level signal, executes a first maintenance process (a process that performs maintenance on some of the nozzle rows). After executing the first maintenance process, if predetermined conditions are met, it executes a second maintenance process (a process that performs maintenance on the remaining nozzle rows). After executing the first and second maintenance processes, it executes an ejection process that ejects ink from the plurality of nozzles 33 onto the sheet.

[0102] Therefore, when cartridge 37 is installed and the ink level reaches the position of the first sensor 41, maintenance processing is performed in advance for some nozzle rows, and then, when predetermined conditions are met, maintenance processing is performed for the remaining nozzle rows. This allows maintenance processing to start early and ink ejection to begin early when cartridge 37 is installed and new ink is supplied.

[0103] Each of the multiple nozzle rows has an exhaust port 71. The control unit 60 performs a suction purge and an exhaust purge as maintenance processing for the head 32. In the first maintenance processing, the control unit 60 performs at least one of the suction purge and the exhaust purge on some of the nozzle rows. This makes it possible to perform at least one of the suction purge and the exhaust purge on some of the nozzle rows in the first maintenance processing.

[0104] The control unit 60 performs a second maintenance process in response to receiving a high-level signal from the second sensor 42 after performing the first maintenance process. By performing the second maintenance process in response to the ink level reaching the position of the second sensor 42 after performing the first maintenance process, the second maintenance process can be performed after the amount of ink required for the second maintenance process has been stored in the sub-tank 35.

[0105] The printer 10 further includes a display unit 16 that functions as an alarm. The control unit 60 activates the alarm when it does not receive a high-level signal from the second sensor 42 after performing the first maintenance process. By issuing an alarm when the ink level does not reach the second position after performing the first maintenance process, the user can take action such as replacing the cartridge 37.

[0106] After activating the alarm, the control unit 60 does not perform the first maintenance process if it receives a high-level signal from the first sensor 41, but performs the second maintenance process if it receives a high-level signal from the second sensor 42. Therefore, by omitting the first maintenance process when it has already been performed, ink consumed during the maintenance process can be saved.

[0107] The control unit 60 performs a third maintenance process during the purging process, which performs maintenance on all of the multiple nozzle rows. When the control unit 60 performs the third maintenance process, it performs the maintenance process with a first amount of ink in response to receiving a high-level signal from the second sensor 42, and performs the maintenance process with a second amount of ink, which is less than the first amount, in response to receiving a low-level signal from the second sensor 42 and a high-level signal from the first sensor 41, so that the third maintenance process can be performed with ink supplied from the sub-tank 35. When the ink level is higher than the position of the first sensor 41 and lower than the position of the second sensor 42, the maintenance process is performed with a smaller amount of ink than usual, so that the maintenance process can be performed on all of the multiple nozzle rows with ink supplied from the sub-tank 35.

[0108] The control unit 60 performs the following processes in the dot counting process: calculating the sensor dot count C1, calculating the sensor dot count C2, and calculating the cumulative ink consumption based on the sensor dot count C2 until a low-level signal is received from the second sensor 42 and from the first sensor 41, and based on the sensor dot count C1 and a fixed value (V2-V1) after the low-level signal is received from the first sensor 41. Therefore, the accuracy of calculating the cumulative ink consumption can be improved by using the ink consumption amount calculated when the ink level drops to a predetermined position.

[0109] [Differentiation] Various modifications can be made to the printer 10 according to the above embodiment. The first sensor 41 and the second sensor 42 of the printer 10 are configured to output a signal corresponding to the liquid level of the ink stored in the sub-tank 35. In the modified printer, the liquid level sensor may output a signal corresponding to the liquid level of the ink stored in the cartridge that supplies ink to the tank. The liquid level sensor only needs to output a signal corresponding to the liquid level of the cartridge that supplies ink to the tank or the ink stored in the tank.

[0110] The control unit 60 of the printer 10 is configured to perform an exhaust purge of the first nozzle row K1 in the first maintenance process, which is executed in response to the first sensor 41 changing from OFF to ON. In the modified printer, the control unit may perform a suction purge of the first nozzle row K1 in the first maintenance process, or perform an exhaust purge or a part of a suction purge of the second to fourth nozzle rows K2 to K4. In the modified printer, the control unit may perform at least one of a suction purge and an exhaust purge on one or more of the nozzle rows of the plurality of nozzle rows in the first maintenance process. In this case, the position of the first sensor 41 should be set to a position where it can detect the amount of ink required in the first maintenance process. Also, the position of the second sensor 42 should be set to a position where it can detect the amount of ink required in the second maintenance process.

[0111] The control unit 60 of the printer 10 is configured to perform a second maintenance process after the first maintenance process is performed, depending on whether the signal received from the second sensor 42 is a high-level signal. In this configuration, "the signal received from the second sensor 42 is a high-level signal (third signal)" is an example of a predetermined condition. In the modified printer, the control unit may perform a second maintenance process after the first maintenance process is performed, depending on whether a predetermined time has elapsed since a high-level signal was received from the first sensor 41. In this case, "a predetermined time has elapsed since the signal received from the first sensor 41 changed to a high-level signal" is an example of a predetermined condition. The modified printer only needs to be equipped with the first sensor 41, and does not necessarily need to be equipped with the second sensor 42.

[0112] It is expected that the sub-tank 35 will have stored the amount of ink necessary for the second maintenance process once a predetermined time has elapsed since the ink level reached the position of the first sensor 41. By performing the second maintenance process at this point, the timing for performing the second maintenance process can be determined using a single liquid level sensor.

[0113] The printer 10 includes a sub-tank 35 connected to the cartridge 37, which stores the ink supplied from the cartridge 37 (cartridge model). In a cartridge model printer, new ink is supplied to the printer when a new cartridge 37 is installed in the mounting case 36. In a modified version, the printer may have a tank with an ink inlet instead of the sub-tank 35 (tank model). In a tank model printer, new ink is supplied to the printer when the user pours ink contained in an ink bottle into the tank's inlet.

[0114] Printer 10 is configured to perform an initial setup purge process as a maintenance process for the print head 32. Printer 10 may also perform a periodic maintenance process for the print head 32, or it may perform a maintenance process at a time instructed by the user.

[0115] The maintenance unit 51 of the printer 10 is equipped with four nozzle caps 52 and an exhaust port cap 53, with the exhaust port cap 53 corresponding to four exhaust ports. In the modified version, the printer maintenance unit may be equipped with a nozzle cap facing the first nozzle row K1 and nozzle caps corresponding to the second to fourth nozzle rows K2 to K4 in order to perform exhaust purging for the first nozzle row K1 and exhaust purging for the second to fourth nozzle rows K2 to K4 at different timings. In addition, the printer maintenance unit in the modified version may be equipped with four exhaust port caps corresponding to four exhaust ports. [Explanation of Symbols]

[0116] 10. Printer (liquid ejection device) 16. Display unit (alert device) 32 heads 33... Nozzle 35... Sub-tank (tank) 37... cartridge 41...First Sensor 42...Second Sensor 60... Control Unit 71... Exhaust port

Claims

1. A tank for storing liquid, A head including multiple nozzles for discharging the liquid supplied from the above tank, A first sensor outputs a first signal when the liquid level of a cartridge supplying liquid to the tank or the liquid stored in the tank is at or above a first position, and outputs a second signal when the liquid level is below the first position. A second sensor outputs a third signal when the liquid level is higher than the first position (a second position) and outputs a fourth signal when the liquid level is lower than the second position. It comprises a control unit and, The above-mentioned multiple nozzles are arranged in a first direction to form multiple nozzle rows, Each of the above multiple nozzle rows has an exhaust port, The above control unit, After receiving the second signal from the first sensor, a first maintenance process is performed to perform maintenance on a portion of the nozzle rows included in the head, in response to receiving the first signal. After performing the first maintenance process described above, a second maintenance process is performed to perform maintenance on the remaining nozzle rows included in the head, in response to receiving the third signal from the second sensor. As part of the maintenance process for the head, a suction purge is performed to suck the nozzles within the nozzle row, and an exhaust purge is performed to suck the exhaust ports of the nozzle row. In the first maintenance process described above, at least one of the above suction purge and the above exhaust purge is performed on some of the nozzle rows. A liquid dispensing device that, after performing the first maintenance process and the second maintenance process described above, performs a dispensing process in which liquid is discharged from the plurality of nozzles onto a sheet.

2. In addition to the alarm system, The liquid dispensing device according to claim 1, wherein the control unit activates the alarm device in response to not receiving the third signal from the second sensor after performing the first maintenance process.

3. The liquid dispensing device according to claim 2, wherein the control unit, after activating the alarm, does not perform the first maintenance process in response to receiving the first signal from the first sensor, and performs the second maintenance process in response to receiving the third signal from the second sensor.

4. The control unit performs a third maintenance process that performs maintenance on all of the plurality of nozzle rows. The liquid dispensing device according to claim 1, wherein the control unit, when executing the third maintenance process, executes the maintenance process with a first amount of liquid in response to receiving the third signal from the second sensor, and executes the maintenance process with a second amount of liquid which is less than the first amount, in response to receiving the fourth signal from the second sensor and the first signal from the first sensor, so that the third maintenance process can be executed with liquid supplied from the tank.

5. The above control unit, A process for calculating a first consumption amount, which is the amount of liquid consumed after the signal received from the first sensor changes from the first signal to the second signal, A process for calculating a second consumption amount, which is the amount of liquid consumed after the signal received from the second sensor changes from the third signal to the fourth signal, A liquid dispensing device according to claim 1, which performs a process of calculating cumulative liquid consumption based on the second consumption amount after receiving the fourth signal from the second sensor and until receiving the second signal from the first sensor, and after receiving the second signal from the first sensor, based on the first consumption amount and a fixed value.

Images