Ink jet printer

Abstract

To more reliably determine settlement of a pigment in a pigmented ink.SOLUTION: An ink jet printer comprises: an ink container in which a pigmented ink containing a pigment P and a solvent S is accumulated; an ink head which discharges the pigmented ink; an ink channel which includes a transparent pipe 72d that transmits light, and connects the ink container and the ink head; a sensor 77 which can detect a concentration of the pigment P; and a determination device. The sensor 77 comprises: a light projection part 77a for irradiating the transparent pipe 72d with light; and a light receiving part 77b for receiving light radiated by the light projection part 77a and reflected by the pigmented ink in the transparent pipe 72d or transmitted through the pigmented ink in the transparent pipe 72d, and detects the concentration of the pigment P on the basis of an amount of light received by the light receiving part 77b. The determination device determines that the pigment P exceeds an allowable range and settles when the concentration detected by the sensor 77 is lower than a predetermined threshold.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an inkjet printer. [Background technology]

[0002] Inkjet printers that print using pigment ink in which the pigment is dispersed in a solvent have been known for some time. Because the pigment in pigment ink is insoluble in the solvent and settles if left unattended, some inkjet printers are configured to agitate the pigment ink in a timely manner. Furthermore, some inkjet printers are equipped with a mechanism for determining whether the pigment has settled. For example, Patent Document 1 discloses an ink-head-type drawing device that detects the flow velocity of pigment ink sucked from a cap after flushing and determines whether the pigment ink concentration is appropriate based on the detected flow velocity. According to Patent Document 1, if the pigment has separated from the solvent, the proportion of solvent in the pigment ink increases, and the detected flow velocity increases. The drawing device described in Patent Document 1 determines that separation of the pigment ink has not occurred if the detected flow velocity is within a reference flow velocity range. If the drawing device described in Patent Document 1 determines that separation of the pigment ink has occurred, it performs an agitation operation on the pigment ink.

[0003] Patent Document 1 also discloses a method for determining whether the density of pigment ink is appropriate by using an optical sensor that detects pigment ink passing a specific position on the suction tube. According to this method, the drawing device determines that separation of the pigment ink has not occurred if the time from the start of suction to the detection of the pigment ink is within a reference time range. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-126112 Summary of the Invention [Problem to be solved by the invention]

[0005] The determination of pigment ink sedimentation by the drawing device of Patent Document 1 depends on the fluidity of the pigment ink. The fluidity of pigment ink is easily affected by factors other than pigment sedimentation, and the determination of pigment ink sedimentation described in Patent Document 1 cannot be said to be highly reliable.

[0006] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide an inkjet printer that can more reliably determine whether the sedimentation of pigment in pigment ink is within an acceptable range. [Means for solving the problem]

[0007] The inkjet printer disclosed herein includes an ink container that stores a pigment ink containing a pigment and a solvent, an ink head that ejects the pigment ink, an ink flow path that includes a transparent tube that transmits light and connects the ink container to the ink head, a sensor that can detect the concentration of the pigment, and a determination device. The sensor includes a light-emitting unit that irradiates the transparent tube with light, and a light-receiving unit that receives light that is irradiated by the light-emitting unit and reflected by the pigment ink in the transparent tube or that has transmitted through the pigment ink in the transparent tube, and is configured to detect the concentration of the pigment based on the amount of light received by the light-receiving unit. The determination device determines that the pigment has settled beyond an acceptable range if the concentration detected by the sensor is lower than a predetermined threshold.

[0008] The inkjet printer can detect the pigment concentration of the pigment ink using a sensor. In pigment ink, the pigment concentration accurately reflects the degree of pigment sedimentation. Therefore, the inkjet printer can more reliably determine whether the pigment sedimentation in the pigment ink is within an acceptable range. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a front view of a printer according to an embodiment. [Figure 2]FIG. 2 is a schematic diagram illustrating the configuration of a white ink supply system. [Figure 3] FIG. 2 is a schematic front view of the sensor attached to the sensor attachment portion. [Figure 4] FIG. 10 is a schematic front view showing another mounting mode of the sensor. [Figure 5] 1 is a block diagram of a printer according to a first embodiment. [Figure 6] 5 is a flowchart showing an ink circulation process according to the first embodiment. [Figure 7] 4 is a graph showing a change in sensor voltage over time in the first embodiment. [Figure 8] FIG. 10 is a block diagram of a printer according to a second embodiment. [Figure 9] 10 is a graph showing a change in sensor voltage over time in the second embodiment. [Figure 10] 10 is a graph showing the relationship between the voltage difference between the sensor voltage and the threshold value and the driving time of the liquid feed pump in the second embodiment. [Figure 11] 10 is a flowchart showing an ink circulation process according to a second embodiment. [Figure 12] FIG. 10 is a block diagram of a printer according to a modified example of the second embodiment. [Figure 13] 10 is a graph showing the relationship between the voltage difference between the sensor voltage and the threshold value and the driving time of the liquid feed pump in a modified example of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] [First embodiment] An inkjet printer according to one embodiment will be described below with reference to the drawings. It should be noted that the embodiment described here is not intended to limit the present invention. Furthermore, the same reference numerals are used to designate components and parts that perform the same functions, and redundant descriptions will be omitted or simplified as appropriate. In the following description, when viewing the inkjet printer from the front, the side away from the inkjet printer is referred to as the front, and the side approaching the inkjet printer is referred to as the rear. Furthermore, the reference numerals F, Rr, L, R, U, and D in the drawings represent the front, rear, left, right, top, and bottom, respectively. However, these directions are merely provided for the convenience of explanation and do not limit the installation manner of the inkjet printer, etc.

[0011] 1 is a front view of an inkjet printer (hereinafter referred to as "printer") 10 according to one embodiment. The printer 10 transports a roll-shaped recording medium 5 in the front-to-rear direction and forms an image on the recording medium 5 by ejecting ink from an ink head 50 mounted on a carriage 40 that moves in the left-to-right direction.

[0012] The recording medium 5 is an object on which an image is printed. There are no particular limitations on the recording medium 5. For example, the recording medium 5 may be paper such as plain paper or inkjet printing paper, or may be a resin sheet. For example, the recording medium 5 may be a thin metal plate or fabric.

[0013] As shown in FIG. 1, the printer 10 includes a platen 20, a transport device 30 for a recording medium 5, a carriage 40, a plurality of ink heads 50 mounted on the carriage 40, a carriage moving device 60, an ink supply system 70 that supplies ink to the plurality of ink heads 50, and a control device 100.

[0014] The platen 20 supports the recording medium 5. Printing on the recording medium 5 is performed on the platen 20. The platen 20 extends in the left-right and front-rear directions. The recording medium 5 on the platen 20 is moved in the front-rear direction by a conveying device 30. The conveying device 30 includes a grit roller 31, a pinch roller 32, and a feed motor 33. The grit roller 31 is embedded in the platen 20. The grit roller 31 receives a driving force from the feed motor 33 and rotates in the front-rear direction. The pinch roller 32 is provided above the platen 20. The pinch roller 32 is provided in a position opposite the grit roller 31 and moves in the up-down direction. When the grit roller 31 rotates with the recording medium 5 sandwiched between the grit roller 31 and the pinch roller 32, the recording medium 5 is conveyed in the front-rear direction.

[0015] The carriage 40 is located above the platen 20. The carriage 40 is equipped with a plurality of ink heads 50. Each ink head 50 ejects ink downward. The ink heads 50 are arranged side by side in the left-right direction. A plurality of nozzles 51 (see FIG. 2) that eject ink are formed on the underside of each ink head 50.

[0016] The carriage moving device 60 moves the carriage 40 in the left-right direction. The carriage moving device 60 includes a guide rail 61, an endless belt 62, left and right pulleys 63L and 63R, and a carriage motor 64. The guide rail 61 extends in the left-right direction. The carriage 40 is slidably engaged with the guide rail 61. The belt 62 is wound around a pulley 63R provided on the right side of the guide rail 61 and a pulley 63L provided on the left side. The carriage motor 64 is connected to one of the pulleys, in this case the right pulley 63R. When the carriage motor 64 is driven, the pulley 63R rotates and the belt 62 moves. This causes the carriage 40 to move in the left-right direction along the guide rail 61.

[0017] The ink supply system 70 supplies ink to the multiple ink heads 50. The ink supply system 70 includes multiple systems, each of which has an ink cartridge 71. In this embodiment, multiple systems of the ink supply system 70 are connected to one ink head 50. Ink supplied by the multiple systems is ejected from one ink head 50. However, only one system of the ink supply system 70 may be connected to one ink head 50. The multiple systems of the ink supply system 70 each supply, for example, CMYK process color ink, white ink, gloss (transparent) ink, etc. The multiple systems of the ink supply system 70 are configured similarly here. Therefore, the following describes the configuration of one system of the ink supply system 70, specifically the system that supplies white ink, and omits description of the other systems. However, some of the multiple systems of the ink supply system 70 may have a configuration different from that described below.

[0018] Fig. 2 is a schematic diagram showing the configuration of a white ink supply system in the ink supply system 70. As shown in Fig. 2, the ink supply system 70 (white ink supply system) includes an ink cartridge 71, an ink flow path 72, a main valve 73, a liquid feed pump 74, a circulation valve 75, a damper 76, and a sensor 77.

[0019] The ink cartridge 71 is an example of an ink container that contains ink. The ink cartridge 71 contains a pouch that stores ink. However, the ink container is not limited to the ink cartridge 71. The ink container may be, for example, a pouch, or a container that stores ink that is replenished from a bottle or the like.

[0020] White ink is a pigment ink containing a white pigment and a solvent. The pigment is a powder used for coloring and is insoluble in the solvent. The pigment does not dissolve in the solvent but floats within it. When white ink is left standing, the pigment settles. However, white ink is an example of a pigment ink containing a pigment and a solvent, and the pigment ink is not limited to white ink. Other examples of pigment inks include metallic ink. Suitable examples of solvents include organic solvents. However, the solvent is not limited to organic solvents and may be, for example, water (which may contain additives). The materials of the pigment and solvent are not particularly limited. The ink supply system 70 only needs to include at least one system for supplying pigment ink to the ink head 50, and may also be configured to supply inks other than pigment ink, such as dye ink.

[0021] The ink flow path 72 connects the ink cartridge 71 and the ink head 50. As shown in FIG. 2, the ink flow path 72 includes a supply flow path 72a that connects the ink cartridge 71 and the ink head 50, and a bypass flow path 72b that bypasses a portion of the supply flow path 72a. The upstream end of the bypass flow path 72b is connected to the supply flow path 72a at a branch point 72c that is provided downstream of the ink cartridge 71. The downstream end of the bypass flow path 72b is connected to the supply flow path 72a at a damper 76 that is provided at the downstream end of the supply flow path 72a. The bypass flow path 72b and the portion of the supply flow path 72a between the branch point 72c and the damper 76 form an annular circulation flow path 72R. White ink is circulated through the circulation flow path 72R.

[0022] In this embodiment, most of the ink flow path 72, excluding the branching portion 72c and the like, is formed by flexible tubing. At least a portion of the ink flow path 72 is formed by transparent tubing that transmits light. The tubing of the ink flow path 72 may be partially or entirely transparent tubing. As will be described in detail later, a sensor 77 is attached to a portion of the transparent tubing. The portion of the transparent tubing where the sensor 77 is attached is an example of a transparent tube that transmits light and on which the sensor 77 is attached. Hereinafter, this portion of the transparent tubing where the sensor 77 is attached will also be referred to as the sensor attachment portion 72d. Herein, the sensor attachment portion 72d is provided in the bypass flow path 72b. However, the location of the sensor attachment portion 72d is not particularly limited. The sensor attachment portion 72d may be provided in the supply flow path 72a. There may be multiple sensor attachment portions 72d and multiple sensors 77. The sensor attachment portion 72d is preferably located in a location where the white ink pigment is likely to settle.

[0023] The main valve 73 is provided in the supply flow path 72a. When the circulation valve 75 is open, ink is supplied from the ink cartridge 71 to the ink head 50 through the circulation valve 75, and the main valve 73 is a valve that prevents ink from dripping from the nozzles 51. The main valve 73 is closed when the circulation valve 75 is open.

[0024] The liquid feed pump 74 is provided in the supply flow path 72a. Here, the liquid feed pump 74 is provided downstream of the branching portion 72c and upstream of the damper 76. When driven, the liquid feed pump 74 feeds ink from the ink cartridge 71 toward the ink head 50. When stopped, the liquid feed pump 74 closes the supply flow path 72a. As will be described in more detail later, the liquid feed pump 74 is also provided in the ink flow path 72 and circulates the white ink through the circulation flow path 72R. There are no limitations on the type of liquid feed pump 74, and it may be, for example, a tube pump, a diaphragm pump, or the like.

[0025] The circulation valve 75 is provided in the bypass flow path 72b. The circulation valve 75 opens and closes the bypass flow path 72b. The circulation valve 75 is closed when ink is supplied to the ink head 50, and is open when ink is circulating in the circulation flow path 72R.

[0026] The damper 76 is provided immediately before the ink head 50. The damper 76 has a storage chamber in which ink is temporarily stored, and reduces fluctuations in ink pressure. The damper 76 is provided with a pressure detection device 76a that detects the pressure in the storage chamber. When the pressure detected by the pressure detection device 76a falls below a predetermined pressure, the control device 100 drives the liquid feed pump 74 to supply ink to the damper 76. When the pressure detected by the pressure detection device 76a exceeds the predetermined pressure, the control device 100 stops the liquid feed pump 74.

[0027] The sensor 77 detects the pigment concentration of the white ink in the sensor mounting portion 72d. In this example, the sensor 77 is an RGB color sensor. FIG. 3 is a schematic front view of the sensor 77 mounted on the sensor mounting portion 72d. As shown in FIG. 3, the sensor 77 includes a light-emitting portion 77a, a light-receiving portion 77b, a signal-transmitting portion 77c, and a mounting fixture 77d.

[0028] The light-emitting unit 77a emits light onto the sensor mounting portion 72d. Here, the light-emitting unit 77a emits three colors of light: red, green, and blue (RGB). The light emitted from the light-emitting unit 77a passes through the transparent tube and is partially reflected by the white ink. The light-receiving unit 77b receives the light emitted by the light-emitting unit 77a and reflected by the white ink in the sensor mounting portion 72d. The sensor 77 is configured to detect the pigment concentration of the white ink (hereinafter, also referred to as ink concentration) based on the amount of light received by the light-receiving unit 77b. Here, the sensor 77 detects the ink color (here, white) from the RGB ratio of the reflected light received by the light-receiving unit 77b, and detects the pigment concentration of the white ink from the amount of reflected light. If the pigment settles in the ink flow path 72, the pigment concentration at the sensor mounting portion 72d decreases. In FIG. 3, the solvent is indicated by the symbol S, and the pigment is indicated by the symbol P. As shown in FIG. 3, when the pigment P settles in the ink flow path 72, the light receiving section 77b receives light reflected by the supernatant solvent S where the pigment P is less.

[0029] The pigment concentration may be a relative concentration relative to the concentration when the pigment P is sufficiently dispersed in the solvent S, and does not necessarily have to be an accurate concentration expressed as, for example, a volume percent. Using the same principle, the sensor 77 can also measure the concentration of inks of other colors.

[0030] However, the method by which the sensor 77 detects the pigment concentration of the ink is not limited to the above. For example, the sensor 77 may be configured to emit monochromatic light. Furthermore, for example, the sensor 77 may be a sensor (e.g., an infrared sensor that emits infrared light) that includes a light-emitting unit 77a and a light-receiving unit 77b arranged opposite each other across the sensor mounting portion 72d, and measures the pigment concentration by utilizing the scattering of irradiated light by the pigment in the ink. In this case, the light-receiving unit 77b receives light that is irradiated by the light-emitting unit 77a and transmitted through the white ink in the sensor mounting portion 72d. The amount of light received by the light-receiving unit 77b increases as the pigment concentration decreases (the more sedimentation occurs).

[0031] The signal transmitting unit 77c transmits a signal corresponding to the detected density of white ink to the control device 100. Here, the signal transmitting unit 77c transmits a voltage signal corresponding to the detected density of white ink to the control device 100. Hereinafter, the voltage of the signal transmitted by the sensor 77 will also be referred to as the sensor voltage. However, the signal transmitting unit 77c may be configured to, for example, pass a current corresponding to the density of white ink to the signal receiving unit 101 (see FIG. 5) of the control device 100. The sensor voltage may be set to be higher as the density of white ink increases, or may be set to be lower as the density of white ink increases. Here, the sensor voltage is set to be higher as the density of white ink increases.

[0032] The mounting fixture 77d fixes a case housing the light-emitting unit 77a and the light-receiving unit 77b to the outer peripheral surface of the sensor mounting unit 72d. As shown in FIG. 3, the sensor mounting unit 72d includes a portion extending non-vertically (hereinafter also referred to as the non-vertical portion 72d1), and the light-emitting unit 77a and the light-receiving unit 77b are disposed above the non-vertical portion 72d1. In the non-vertical portion 72d1, the ink pigment P settles along the bottom of the tube. Therefore, the supernatant solvent S faces the light-emitting unit 77a and the light-receiving unit 77b disposed above the non-vertical portion 72d1. As a result, when the pigment P settles, this can be reliably detected.

[0033] However, the location of the light-projecting unit 77a and the light-receiving unit 77b is not limited to above the non-vertical portion 72d1. FIG. 4 is a schematic front view showing another mounting configuration of the sensor 77. As shown in FIG. 4, the light-projecting unit 77a and the light-receiving unit 77b may be disposed to the side of the non-vertical portion 72d1. In the non-vertical portion 72d1, the pigment P settles along the bottom of the tube. Therefore, even when the light-projecting unit 77a and the light-receiving unit 77b are disposed to the side of the non-vertical portion 72d1, the supernatant solvent S faces the light-projecting unit 77a and the light-receiving unit 77b. Therefore, when the pigment P settles, this can be reliably detected.

[0034] The control device 100 controls the operation of each component. Figure 5 is a block diagram of the printer 10. As shown in Figure 5, the control device 100 is electrically connected to the feed motor 33, the ink head 50, the carriage motor 64, the main valve 73, the liquid supply pump 74, and the circulation valve 75, and is configured to be able to control them. The control device 100 is also electrically connected to the pressure detection device 76a of the damper 76 and the sensor 77, and receives signals from them.

[0035] The configuration of the control device 100 is not particularly limited. The control device 100 is, for example, a microcomputer. The hardware configuration of the microcomputer is not particularly limited, but may include, for example, an interface (I / F) that receives print data and the like from an external device such as a host computer, a central processing unit (CPU) that executes instructions from a control program, a read-only memory (ROM) that stores the program executed by the CPU, a random access memory (RAM) used as a working area for expanding the program, and a storage device such as a memory that stores the program and various data. Note that the control device 100 does not necessarily have to be provided inside the printer 10. For example, the control device 100 may be a computer or the like that is installed outside the printer 10 and is communicably connected to the printer 10 via a wired or wireless connection.

[0036] 5, the control device 100 determines whether the pigment in the ink has settled, and if so, circulates the ink, and includes a signal receiving unit 101, a determination unit 102, and a circulation control unit 103. The control device 100 may also include other processing units, such as a control unit that controls the printing operation, but these will not be illustrated or described here.

[0037] The signal receiving unit 101 receives the signal transmitted from the sensor 77. This allows the control device 100 to obtain the concentration of the pigment, in other words, to grasp the degree of sedimentation of the pigment.

[0038] If the density detected by the sensor 77 is lower than a predetermined threshold, the determination unit 102 determines that the pigment in the pigment ink has settled beyond the allowable range. The determination unit 102 stores at least a sensor voltage threshold as a threshold related to the density of the white ink. Here, if the sensor voltage is lower than a predetermined threshold V1 (see FIG. 7), the determination unit 102 determines that the pigment in the white ink has settled beyond the allowable range. The threshold V1 is predetermined based on the results of measuring the density of the pigment ink when the pigment has settled to near the lower limit of the allowable range. Note that the threshold related to the density of the pigment ink is not particularly limited as long as it is a physical quantity corresponding to the density of the pigment ink, and may be, for example, a current flowing through the sensor 77.

[0039] In this embodiment, the determination unit 102 determines whether or not there is subsidence at short time intervals, such as one minute. In this embodiment, the determination unit 102 determines whether or not there is subsidence at substantially constant intervals. However, the determination unit 102 may determine whether or not there is subsidence at longer time intervals. A suitable example of control in this case will be described in the second embodiment.

[0040] When the determination unit 102 determines that the pigment has settled beyond the allowable range, the circulation control unit 103 drives the liquid feed pump 74 to circulate the ink within the circulation flow path 72R. Before driving the liquid feed pump 74, the circulation control unit 103 closes the main valve 73 and opens the circulation valve 75. In this embodiment, when the determination unit 102 determines that the pigment has settled beyond the allowable range, the circulation control unit 103 drives the liquid feed pump 74 for a predetermined time.

[0041] [Ink circulation process] The ink circulation process will be described below. FIG. 6 is a flowchart showing the ink circulation process according to this embodiment. As shown in FIG. 6, in step S01 of the circulation process, the sensor voltage Vs is acquired. In step S02, it is determined whether the sensor voltage Vs is lower than the threshold value V1. FIG. 7 is a graph showing the change in the sensor voltage Vs over time. The ink concentration at the point measured by the sensor 77 decreases over time due to the settling of the pigment. Therefore, as shown in FIG. 7, the sensor voltage Vs falls below the threshold value V1 at some point.

[0042] 6, if the sensor voltage Vs is still equal to or greater than the threshold value V1 (if the result of step S02 is NO), steps S01 and S02 are repeated. If the sensor voltage Vs falls below the threshold value V1 (if the result of step S02 is YES), ink circulation begins in step S03. Specifically, the main valve 73 is closed, the circulation valve 75 is opened, and then the liquid feed pump 74 is driven.

[0043] As described above, in this embodiment, because the cycle in which steps S01 and S02 are repeated is short, by the time the result of step S02 becomes YES, the ink concentration is only slightly lower than the threshold. Therefore, in this embodiment, the ink concentration is almost always maintained higher than the threshold. In other words, pigment sedimentation is almost always maintained at a level less severe than the allowable range.

[0044] In step S04, after a predetermined time has elapsed, the circulation of the ink is stopped. Specifically, the liquid feed pump 74 is stopped, the main valve 73 is opened, and the circulation valve 75 is closed.

[0045] In addition to the white ink, when a pigment ink is used for which it is preferable to judge whether or not sedimentation has occurred, the pigment ink may also be subjected to the same judgment of whether or not sedimentation has occurred and the circulation of the pigment ink.

[0046] [Effects of the first embodiment] The following describes the effects that can be achieved by the printer 10 according to this embodiment.

[0047] The printer 10 according to this embodiment includes an ink cartridge 71 containing pigment ink containing a pigment and a solvent, an ink head 50 for ejecting the pigment ink, an ink flow path 72 including a light-transmitting sensor mounting portion 72d and connecting the ink cartridge 71 and the ink head 50, a sensor 77, and a determination unit 102. The sensor 77 includes a light-emitting portion 77a that emits light onto the sensor mounting portion 72d and a light-receiving portion 77b that receives light emitted by the light-emitting portion 77a and reflected by the pigment ink in the sensor mounting portion 72d. The determination unit 102 determines that the pigment has settled beyond an acceptable range if the concentration detected by the sensor 77 is lower than a predetermined threshold. The light-receiving portion 77b of the sensor 77 may be configured to receive light emitted by the light-emitting portion 77a and transmitted through the pigment ink in the sensor mounting portion 72d.

[0048] The printer 10 can determine whether the pigment has settled beyond an acceptable range. Therefore, for example, when circulating pigment ink to eliminate pigment settling, excessive or insufficient circulation can be prevented. For example, in a method in which ink is circulated at predetermined time intervals, the degree of pigment settling is not detected, which can result in excessive or insufficient circulation.

[0049] The printer 10 according to this embodiment also detects the pigment concentration of the pigment ink using a sensor 77. In pigment ink, the pigment concentration accurately reflects the degree of pigment sedimentation. Therefore, the printer 10 according to this embodiment can reliably determine whether pigment sedimentation in the pigment ink is within an acceptable range. In prior art techniques, such as the drawing device disclosed in Patent Document 1, determining whether pigment ink has sedimented depends on the fluidity of the pigment ink. However, the fluidity of pigment ink is easily affected by factors other than pigment sedimentation, such as the temperature of the ink and the state of the suction device. Therefore, the printer 10 according to this embodiment can more reliably determine whether pigment sedimentation is within an acceptable range than methods that detect the fluidity of the pigment ink.

[0050] Furthermore, the printer 10 according to this embodiment detects the concentration of pigment ink in the ink flow path 72. Therefore, unlike the method described in Patent Document 1, there is no need to eject ink from the ink head, which makes it possible to reduce ink consumption.

[0051] In this embodiment, the ink flow path 72 includes a circular circulation flow path 72R through which the pigment ink is circulated. The printer 10 is provided with a liquid feed pump 74 that is provided in the ink flow path 72 and circulates the pigment ink through the circulation flow path 72R, and a circulation control unit 103 that drives the liquid feed pump 74 when a determination unit 102 determines that the pigment has settled beyond an acceptable range. With this configuration, when the pigment has settled beyond an acceptable range, the pigment ink is circulated and agitated through the circulation flow path 72R, thereby eliminating the settling.

[0052] In this embodiment, the sensor mounting portion 72d includes a non-vertical portion 72d1 that extends non-vertically, and the light-emitting portion 77a and the light-receiving portion 77b are disposed above the non-vertical portion 72d1. With this configuration, when the pigment settles, the supernatant solvent of the pigment ink faces the light-emitting portion 77a and the light-receiving portion 77b for the reasons described above. Therefore, when the pigment settles, this can be reliably detected. Note that the same effect can be achieved even when the light-emitting portion 77a and the light-receiving portion 77b are disposed to the side of the non-vertical portion 72d1.

[0053] [Second embodiment] In the second embodiment, the ink circulation time is determined according to the degree of pigment sedimentation. In the following description of the second embodiment and its modifications, components that perform the same functions as those in the first embodiment will be designated by the same reference numerals as those in the first embodiment. Furthermore, duplicated descriptions will be omitted or simplified as appropriate.

[0054] In this embodiment, the circulation control unit 103 determines the time for driving the liquid feed pump 74 in accordance with the concentration (sensor voltage Vs) detected by the sensor 77. More specifically, the lower the concentration detected by the sensor 77, the longer the time for driving the liquid feed pump 74 is set by the circulation control unit 103. FIG. 8 is a block diagram of the printer 10 according to this embodiment. As shown in FIG. 8, in this embodiment, the circulation control unit 103 includes a circulation time calculation unit 103a. The circulation time calculation unit 103a is configured to input the concentration (sensor voltage Vs) detected by the sensor 77 into a pre-registered calculation formula and determine the time for driving the liquid feed pump 74.

[0055] In this embodiment, the determination unit 102 determines whether or not pigment has settled over a long period of time, such as one hour. Therefore, the degree of pigment settling varies each time the determination is made. The lower the concentration detected by the sensor 77, the greater the amount of pigment settling, so the circulation control unit 103 increases the time for which the liquid feed pump 74 is driven. The higher the concentration detected by the sensor 77, the less pigment has settled, so the circulation control unit 103 decreases the time for which the liquid feed pump 74 is driven.

[0056] 9 is a graph showing the change in sensor voltage Vs over time in the second embodiment. As shown in FIG. 9, when the determination of subsidence is made at time point A, for example, the voltage difference ΔV between threshold value V1 and sensor voltage Vs is ΔVa. When the determination of subsidence is made at time point B, for example, the voltage difference ΔV between threshold value V1 and sensor voltage Vs is ΔVb. In this example, the sensor voltage Vs is smaller at time point B than at time point A (subsidence has progressed), and the voltage difference ΔVb is larger than the voltage difference ΔVa.

[0057] FIG. 10 is a graph showing the relationship between the voltage difference ΔV between the sensor voltage Vs and the threshold value V1 and the drive time T of the liquid feed pump 74. FIG. 10 is a graph of a calculation formula registered in the circulation time calculation unit 103a. As shown in FIG. 10, according to one suitable calculation formula, the drive time T of the liquid feed pump 74 increases in proportion to the voltage difference ΔV between the sensor voltage Vs and the threshold value V1. Therefore, as shown in FIG. 10, the drive time T of the liquid feed pump 74 is longer when circulation is started at time B when the voltage difference ΔV is ΔVb than when circulation is started at time A when the voltage difference ΔV is ΔVa.

[0058] The relational expression used to determine the drive time of the liquid feed pump 74 from the concentration of the pigment ink is preferably set so that the lower the concentration detected by the sensor 77, the longer the drive time of the liquid feed pump 74. However, the relational expression used to determine the drive time of the liquid feed pump 74 from the concentration of the pigment ink is not limited to a linear expression. The relational expression may be set, for example, so that the lower the concentration of the pigment ink (the more sedimentation there is), the longer the drive time of the liquid feed pump 74 (the graph shows a curved graph with a gradually increasing upward gradient on the vertical axis T), or so that the lower the concentration of the pigment ink, the slower the drive time of the liquid feed pump 74 (the graph shows a curved graph with a gradually decreasing upward gradient on the vertical axis T).

[0059] 11 is a flowchart showing the ink circulation process according to this embodiment. As shown in FIG. 11, in step S11 of the circulation process according to this embodiment, the sensor voltage Vs is acquired. In step S12, it is determined whether the sensor voltage Vs is lower than the threshold value V1. If the sensor voltage Vs is equal to or greater than the threshold value V1 (if the result of step S12 is NO), steps S11 and S12 are repeated. However, the next time steps S11 and S12 are performed is after a relatively long predetermined time (for example, one hour).

[0060] If the sensor voltage Vs falls below the threshold value V1 in step S12 (if the result of step S12 is YES), then step S13 determines the drive time of the liquid feed pump 74. The method for determining the drive time of the liquid feed pump 74 is as described above.

[0061] In step S14, the circulation of the ink is started. In step S15, when the time determined in step S13 has elapsed, the circulation of the ink is stopped.

[0062] [Effects of the second embodiment] The following describes the effects that can be achieved by the printer 10 according to this embodiment. In this embodiment, the circulation control unit 103 is configured to determine the time for driving the liquid supply pump 74 according to the concentration detected by the sensor 77. With this configuration, the ink agitation time is determined according to the degree of sedimentation of the pigment in the ink, so that excessive agitation of the ink and insufficient agitation of the ink can be prevented.

[0063] Specifically, the circulation control unit 103 sets a longer time for driving the liquid supply pump 74 as the concentration detected by the sensor 77 decreases. With this configuration, the ink is stirred for a longer period of time as the concentration detected by the sensor 77 decreases, i.e., the pigment sedimentation increases. This more reliably eliminates pigment sedimentation. Furthermore, with this configuration, the ink stirring time is shortened as the concentration detected by the sensor 77 increases within a range lower than the threshold value, i.e., the pigment sedimentation decreases. This makes it possible to suppress a decrease in productivity due to ink stirring.

[0064] [Modification of the second embodiment] The second embodiment can also be implemented, for example, by the following modified example: According to a preferred modified example of the second embodiment, the drive time of the liquid feed pump 74 is increased in stages as the concentration of the pigment detected by the sensor 77 decreases.

[0065] FIG. 12 is a block diagram of a printer according to this modification. As shown in FIG. 12, in this modification, the circulation control unit 103 includes a first registration unit 103b and a second registration unit 103c. The first registration unit 103b registers multiple tiers related to concentrations detected by the sensor 77. The second registration unit 103c registers the drive time of the liquid feed pump 74 for each tier registered in the first registration unit 103b. The drive time of the liquid feed pump 74 registered in the second registration unit 103c is set longer for tiers with lower concentrations. The circulation control unit 103 drives the liquid feed pump 74 for the drive time registered for the tier to which the concentration detected by the sensor 77 belongs.

[0066] FIG. 13 is a graph showing the relationship between the voltage difference ΔV between the sensor voltage Vs and the threshold value V1 and the drive time T of the liquid feed pump 74 in this modified example. As shown in FIG. 13, multiple hierarchies C1 to C4 related to the voltage difference ΔV between the sensor voltage Vs and the threshold value V1 are continuous and border each other. For example, the upper limit of the voltage difference ΔV in hierarchical level C1 is equal to the lower limit of the voltage difference ΔV in hierarchical level C2, which is adjacent to hierarchical level C1. The drive times shown on the vertical axis of the graph in FIG. 13 correspond to the multiple hierarchical levels C1 to C4, respectively. The number of hierarchical levels is not particularly limited.

[0067] As shown in FIG. 13 , for example, when a determination of sedimentation is made at time A and a determination of sedimentation is made at time B are compared, the voltage difference ΔV (ΔVa) at time A and the voltage difference ΔV (ΔVb) at time B belong to the same hierarchy C1. Therefore, the drive time T of the liquid feed pump 74 is the same when the determination of sedimentation is made at time A and when the determination of sedimentation is made at time B. The voltage difference ΔV (ΔVc) at time C belongs to hierarchy C2, where the voltage difference ΔV is larger (the sensor voltage Vs is smaller) than hierarchy C1, to which the voltage differences ΔVa and ΔVb at time A and time B belong. Therefore, the drive time T of the liquid feed pump 74 is longer when the determination of sedimentation is made at time C than when the determination of sedimentation is made at time A or B.

[0068] As in this modified example, the ink agitation time can also be suitably adjusted by gradually increasing the drive time of the liquid feed pump 74 as the pigment concentration detected by the sensor 77 decreases. The ink agitation time does not need to be precise, as long as it is appropriate. Therefore, this configuration also allows the ink agitation time to be suitably adjusted.

[0069] [Other embodiments] Several preferred embodiments have been described above. However, the above-described embodiments are merely examples, and the technology disclosed herein can be embodied in various other forms. For example, in the above-described embodiment, the sensor 77 is attached to a non-vertical pipe in the ink flow path 72, but the sensor 77 may also be attached to a vertical pipe. The transparent pipe is not limited to a transparent tube and may be, for example, a transparent pipe having a fixed shape. The location in the ink flow path where the ink concentration is detected is also not particularly limited. For example, the sensor may be positioned to detect the ink concentration in a damper.

[0070] The configuration of the ink supply system 70 is not limited to that described above. In the above embodiment, the upstream end of the bypass flow path 72b is connected to the supply flow path 72a, and the downstream end is connected to the damper 76. However, for example, the upstream end of the bypass flow path may be connected to an ink cartridge. The downstream end of the bypass flow path may be connected to the supply flow path. Pipes, valves, pumps, etc. may be added or omitted as appropriate.

[0071] In the above embodiment, the determination device that determines that the pigment has settled beyond the allowable range when the concentration detected by the sensor 77 is lower than a predetermined threshold is part of the control device 100 (determination unit 102). However, the determination device may be a device provided separately from the control device 100 that controls the operation of the printer 10.

[0072] The configuration of the inkjet printer is not limited unless otherwise specified. For example, the technology disclosed herein can be used in flatbed inkjet printers. It can also be used in devices that incorporate an inkjet printer, such as an inkjet printer with a cutting head. [Explanation of symbols]

[0073] 10. Inkjet printer 50 ink head 70 Ink supply system 71 Ink cartridges (ink containers) 72 Ink flow path 72R Circulation flow path 72d Sensor mounting part (transparent tube) 72d1 Non-vertical section 74 Liquid transfer pump (pump) 77 Sensors 77a Light projector 77b Light receiving section 100 control device 102 Judgment unit (judgment device) 103 Circulation control unit (drive control device) 103b First Registration Section 103c Second Registration Section

Claims

1. an ink container for storing pigment ink containing a pigment and a solvent; an ink head that ejects the pigment ink; an ink flow path including a transparent tube that transmits light and that connects the ink container and the ink head; a sensor comprising a light projecting unit that projects light onto the transparent tube, and a light receiving unit that receives light that has been projected by the light projecting unit and reflected by the pigment ink in the transparent tube or that has passed through the pigment ink in the transparent tube, the sensor being capable of detecting the concentration of the pigment based on the amount of light received by the light receiving unit; and a determination device that determines that the pigment has settled beyond an allowable range when the concentration detected by the sensor is lower than a predetermined threshold value. Inkjet printer.

2. the ink flow path includes an annular circulation flow path through which the pigment ink is circulated; a pump provided in the ink flow path to circulate the pigment ink through the circulation flow path; a drive control device that drives the pump when the determination device determines that the pigment has settled beyond an allowable range.

2. The inkjet printer according to claim 1.

3. The drive control device is configured to determine a time for driving the pump depending on the concentration detected by the sensor.

3. The inkjet printer according to claim 2.

4. the drive control device sets a time for driving the pump to be longer as the concentration detected by the sensor is lower; 4. The inkjet printer according to claim 3.

5. The drive control device includes: a first registration unit in which a plurality of hierarchical levels relating to concentrations detected by the sensor are registered; a second registration unit in which the driving time of the pump is registered for each floor registered in the first registration unit, The driving time of the pump registered in the second registration unit is set to be longer for a layer with a lower concentration.

4. The inkjet printer according to claim 3.

6. the transparent tube includes a non-vertical portion extending non-vertically, The light-emitting unit and the light-receiving unit are disposed above the non-vertical portion.

2. The inkjet printer according to claim 1.

7. the transparent tube includes a non-vertical portion extending non-vertically, The light-emitting unit and the light-receiving unit are disposed on the sides of the non-vertical portion.

2. The inkjet printer according to claim 1.

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