Liquid dispensing device and determination method

Abstract

To provide a liquid dispensing device and a determination method capable of detecting a defective nozzle condition caused by increased viscosity of the liquid inside the nozzle. [Solution] The image forming apparatus includes a wiper 72 that wipes off ink IN1 adhering to the nozzle surface 33A of the recording head, an imaging unit 74 that images the nozzle surface 33A after the ink IN1 has been wiped off by the wiper 72, an acquisition processing unit that acquires the amount of ink IN1 drawn out from inside the nozzle 34 to the nozzle surface 33A by the wiper 72 based on the imaging results from the imaging unit 74, and a determination processing unit that determines that the nozzle 34 is in a defective state if the amount of ink IN1 acquired by the acquisition processing unit is less than a first threshold.

Description

Technical Field

[0001] The present invention relates to a liquid ejection device and a determination method.

Background Art

[0002] A liquid ejection device such as an inkjet printer includes a ejection unit and a wiper. The ejection unit has a nozzle surface on which nozzles are formed, and ejects a liquid from the nozzles. The wiper wipes off the liquid adhering to the nozzle surface.

[0003] Further, there is known as a related art a liquid ejection device including an imaging unit that images the nozzle surface, and determining whether the nozzles are in a defective state based on an imaging result by the imaging unit (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the liquid ejection device according to the above-described related art, although it is possible to detect a defective state of the nozzles caused by foreign matter adhering to the nozzles, it is not possible to detect a defective state of the nozzles caused by thickening of the liquid in the nozzles.

[0006] An object of the present invention is to provide a liquid ejection device and a determination method capable of detecting a defective state of a nozzle caused by thickening of a liquid in the nozzle.

Means for Solving the Problems

[0007] A liquid dispensing device according to one aspect of the present invention comprises a dispensing unit, a wiper, an imaging unit, an acquisition processing unit, and a determination processing unit. The dispensing unit has a nozzle surface from which a nozzle is formed, and dispenses liquid from the nozzle. The wiper wipes off the liquid adhering to the nozzle surface. The imaging unit images the nozzle surface after the liquid has been wiped off by the wiper. The acquisition processing unit acquires the amount of liquid drawn from inside the nozzle to the nozzle surface by the wiper based on the imaging results from the imaging unit. The determination processing unit determines that the nozzle is in a defective state if the amount of liquid acquired by the acquisition processing unit is less than a predetermined threshold.

[0008] A determination method relating to another aspect of the present invention is performed in a liquid dispensing device comprising: a dispensing unit having a nozzle surface on which a nozzle is formed and dispensing liquid from the nozzle; a wiper for wiping off the liquid adhering to the nozzle surface; and an imaging unit for imaging the nozzle surface after the liquid has been wiped off by the wiper, and includes an acquisition step and a determination step. In the acquisition step, the amount of liquid drawn from inside the nozzle to the nozzle surface by the wiper is acquired based on the imaging result by the imaging unit. In the determination step, if the amount of liquid acquired in the acquisition step is less than a predetermined threshold, it is determined that the nozzle is in a defective state. [Effects of the Invention]

[0009] According to the present invention, it is possible to detect a defective state of the nozzle caused by increased viscosity of the liquid inside the nozzle. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a cross-sectional view showing the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] Figure 2 is a perspective view showing the configuration of the head unit of an image forming apparatus according to an embodiment of the present invention. [Figure 3]Figure 3 is a plan view showing the configuration of a wipe unit in an image forming apparatus according to an embodiment of the present invention. [Figure 4] Figure 4 is a block diagram showing the configuration of the control unit of an image forming apparatus according to an embodiment of the present invention. [Figure 5] Figure 5 shows the state of the nozzle surface during the wiping process in an image forming apparatus according to an embodiment of the present invention. [Figure 6] Figure 6 is a flowchart showing an example of a defective nozzle detection process performed in an image forming apparatus according to an embodiment of the present invention. [Modes for carrying out the invention]

[0011] The embodiments of the present invention will be described below with reference to the attached drawings. Note that the following embodiments are merely examples of the present invention and do not limit the technical scope of the present invention.

[0012] [Configuration of the image forming apparatus 100] First, the configuration of the image forming apparatus 100 according to an embodiment of the present invention will be described with reference to Figures 1 to 5.

[0013] For the sake of explanation, the vertical direction is defined as the up-down direction D1 when the image forming apparatus 100 is in a usable installation state (as shown in Figure 1). The front-to-back direction D2 is defined with the front side of the image forming apparatus 100 shown in Figure 1 facing the viewer. The left-to-right direction D3 is defined with respect to the front side of the image forming apparatus 100 in the aforementioned installation state.

[0014] The image forming apparatus 100 is an inkjet printer capable of forming an image on a sheet using an inkjet method. The image forming apparatus 100 is an example of a liquid ejection device of the present invention. Furthermore, the ink IN1 (see Figure 5) used for image formation is an example of a liquid of the present invention.

[0015] As shown in Figures 1 and 4, the image forming apparatus 100 comprises a paper feeding unit 1, an image forming unit 2, a maintenance unit 3, an operation display unit 4, a storage unit 5, and a control unit 6.

[0016] The sheet feeding unit 1 supplies sheets to the image forming unit 2.

[0017] As shown in FIG. 1, the sheet feeding unit 1 includes a sheet feeding cassette 11 and a sheet feeding unit 12. The sheet feeding cassette 11 accommodates sheets on which images are formed by the image forming unit 2. The sheet feeding unit 12 takes out the uppermost sheet among a plurality of sheets (sheet bundle) accommodated in the sheet feeding cassette 11 and sends out the taken-out sheet to a conveyance path 13 (see FIG. 1). In the image forming apparatus 100, sheets are conveyed along the conveyance path 13 (see FIG. 1) passing through the image forming unit 2 from the sheet feeding cassette 11. In FIG. 1, the conveyance path 13 is indicated by a dashed-dotted line.

[0018] The image forming unit 2 forms an image on the sheet supplied by the sheet feeding unit 1 by an inkjet method. Specifically, the image forming unit 2 forms an image on the sheet using four colors of ink IN1 (see FIG. 5), namely black, cyan, magenta, and yellow. For example, the ink IN1 is an aqueous ink whose main solvent is water.

[0019] As shown in FIG. 1, the image forming unit 2 includes a head unit 21 and a conveyance unit 22.

[0020] As shown in FIGS. 1 and 2, the head unit 21 includes four line heads 31 corresponding to the four colors of ink IN1 and a support portion 32.

[0021] As shown in FIG. 2, each of the line heads 31 is long in the width direction D5 (see FIG. 2) orthogonal to the sheet conveyance direction D4 (see FIG. 2). The width direction D5 is the same direction as the front-rear direction D2. Specifically, each of the line heads 31 has a length corresponding to the width of the largest-size sheet that can be accommodated in the sheet feeding cassette 11 in the width direction D5. The four line heads 31 are arranged at equal intervals along the conveyance direction D4.

[0022] As shown in Figure 2, each line head 31 is equipped with three recording heads 33. The recording heads 33 eject ink IN1 (see Figure 5) toward the sheet being transported by the transport unit 22. Specifically, the surface of the recording head 33 facing the sheet (bottom surface) is provided with a plurality of nozzles 34 (see Figure 5) used for ejecting ink IN1. Hereinafter, the surface of the recording head 33 on which the nozzles 34 are formed will be referred to as the "nozzle surface 33A" (see Figures 1 and 5). The plurality of nozzles 34 are arranged along the width direction D5 (an example of a specific direction in the present invention) on the nozzle surface 33A. The recording head 33 ejects ink IN1 from each of the nozzles 34. The recording head 33 is an example of the ejection unit of the present invention.

[0023] The recording head 33 also includes a pressurized chamber (not shown), an ejection element (not shown), and an individual flow path (not shown) corresponding to each nozzle 34. The pressurized chamber communicates with the nozzle 34 and contains ink IN1. The ejection element ejects ink IN1 from the nozzle 34 in response to a drive signal input. For example, the ejection element is a piezoelectric element. The individual flow path is an ink flow path provided between the pressurized chamber and a common flow path (not shown) common to the multiple nozzles 34. Multiple individual flow paths corresponding to the multiple nozzles 34 are connected to the common flow path. The common flow path is connected to an ink supply unit (not shown) that supplies ink IN1 to each of the pressurized chambers.

[0024] As shown in Figure 2, in each line head 31, the three recording heads 33 are arranged in a staggered pattern along the width direction D5.

[0025] The support section 32 supports four line heads 31. As shown in Figure 2, the support section 32 is formed in a flat plate shape along a horizontal plane. The support section 32 includes a mounting section corresponding to each recording head 33. The recording head 33 is mounted on the mounting section. The mounting section includes a through-hole that penetrates the support section 32 in the vertical direction D1. The bottom portion of the recording head 33 mounted on the mounting section, including the nozzle surface 33A, protrudes downward from the through-hole of the mounting section (see Figure 1).

[0026] The head unit 21 is provided to be movable between an image forming position and a retracted position. In Figure 1, the head unit 21 positioned at the image forming position is shown by a solid line. Also in Figure 1, the head unit 21 positioned at the retracted position is shown by a dashed line. The image forming position is the position of the head unit 21 when an image forming process is performed to form an image on a sheet. The retracted position is a position above the image forming position. In other words, the head unit 21 is provided to be movable in the vertical direction D1. The retracted position is a position retracted above the movement paths of the cap unit 52 (see Figure 1) and the wipe unit 53 (see Figure 1), which move along the left-right direction D3.

[0027] Specifically, the support unit 32 is supported by the housing of the image forming apparatus 100 so as to be movable in the vertical direction D1. The support unit 32 moves in the vertical direction D1 by receiving a driving force supplied from a drive unit (not shown). As the support unit 32 moves, the four line heads 31 supported by the support unit 32 also move.

[0028] Furthermore, the number of line heads 31 provided in the head unit 21 is not limited to four. Also, the number of recording heads 33 included in the line head 31 is not limited to three.

[0029] As shown in Figure 1, the transport unit 22 is positioned below the head unit 21. The transport unit 22 transports the sheet while keeping it facing the recording head 33. As shown in Figure 1, the transport unit 22 includes a transport belt 41 on which the sheet is placed, and a plurality of tension rollers that tension the transport belt 41. The gap between the transport belt 41 and the nozzle surface 33A of the recording head 33 is adjusted so that the gap between the surface of the sheet and the nozzle surface 33A during image formation is a predetermined distance (for example, 1 mm).

[0030] The operation display unit 4 is the user interface of the image forming apparatus 100. The operation display unit 4 has a display unit and an operation unit. The display unit displays various information in response to control instructions from the control unit 6. Specifically, the display unit is a display device such as a liquid crystal display. The operation unit inputs various information to the control unit 6 in response to user operations. Specifically, the operation unit is an operating device including operation keys and a touch panel.

[0031] The memory unit 5 is a non-volatile memory device. For example, the memory unit 5 is a non-volatile memory such as flash memory.

[0032] The control unit 6 comprehensively controls the image forming apparatus 100. As shown in Figure 4, the control unit 6 includes a CPU 81, a ROM 82, and a RAM 83. The CPU 81 is a processor that performs various arithmetic operations. The ROM 82 is a non-volatile memory device in which information such as control programs for causing the CPU 81 to perform various operations is pre-stored. The RAM 83 is a volatile or non-volatile memory device used as a temporary storage memory (work area) for the various operations performed by the CPU 81. The CPU 81 comprehensively controls the image forming apparatus 100 by executing various control programs pre-stored in the ROM 82.

[0033] Furthermore, the control unit 6 may be a separate control unit from the main control unit that comprehensively controls the image forming apparatus 100. Also, the control unit 6 may be composed of electronic circuits such as an integrated circuit (ASIC).

[0034] Maintenance unit 3 is used for maintenance of the head unit 21.

[0035] As shown in Figure 1, the maintenance unit 3 comprises a housing unit 51, a cap unit 52, and a wipe unit 53.

[0036] As shown in Figure 1, the housing section 51 is positioned to the left of the image forming section 2. The housing section 51 houses the cap unit 52 and the wipe unit 53. The housing section 51 is formed in the shape of a rectangular box with the right side open.

[0037] The cap unit 52 caps the nozzle surface 33A. The cap unit 52 comprises a cap portion 61 (see Figure 1) corresponding to each recording head 33, and a support portion 62 (see Figure 1) that supports each cap portion 61. The support portion 62 is formed in a flat plate shape along a horizontal plane. Each cap portion 61 is positioned on the upper surface of the support portion 62. Each cap portion 61 seals the space along the nozzle surface 33A. In other words, each cap portion 61 caps the nozzle surface 33A. The cap portion 61 comprises a bottom portion and a peripheral wall portion. The bottom portion forms a facing surface that faces the nozzle surface 33A. The peripheral wall portion is formed along the edge of the bottom portion. The peripheral wall portion seals the space between the nozzle surface 33A and the bottom portion by surrounding the space on all four sides (front, back, left, and right). The cap portion 61 is made of an elastically deformable material such as rubber. When the nozzle surface 33A is capped, the cap portion 61 is pressed against the nozzle surface 33A from below. This creates a sealed space surrounded by the nozzle surface 33A, the bottom portion, and the peripheral wall portion.

[0038] The cap unit 52 is provided to be movable between a first housing position and a cap position. Figure 1 shows the cap unit 52 positioned in the first housing position. As shown in Figure 1, the first housing position is the position in which the cap unit 52 is housed in the housing portion 51. The cap position is the position in which the cap portion 61 covers the space along the nozzle surface 33A. The cap position is to the right of the first housing position. In other words, the cap unit 52 is provided to be movable in the left-right direction D3. The cap position is also a position between the image forming position and the retracted position.

[0039] Specifically, the support portion 62 of the cap unit 52 is supported by the housing of the image forming apparatus 100 so as to be movable in the left-right direction D3. The support portion 62 moves in the left-right direction D3 by receiving a driving force supplied from a drive unit (not shown).

[0040] In the image forming apparatus 100, when the nozzle surface 33A is capped, the operating mode of the image forming apparatus 100 transitions from the image forming mode, in which the image forming process can be performed, to the cap mode, in which the nozzle surface 33A is capped, in the following procedure. First, the head unit 21 is moved from the image forming position to the retracted position. Next, the cap unit 52 is moved from the first housing position to the cap position. Then, the head unit 21 is moved downward from the retracted position until the nozzle surface 33A is pressed against the cap portion 61 of the cap unit 52. As a result, the nozzle surface 33A is capped.

[0041] The wipe unit 53 performs a wiping process to wipe the nozzle surface 33A. As shown in Figure 3, the wipe unit 53 includes a wiper carriage 71 corresponding to each line head 31. Also as shown in Figure 3, the wipe unit 53 includes a wiper 72 corresponding to each recording head 33, and an imaging unit 74. Furthermore, as shown in Figure 3, the wipe unit 53 includes eight ink trays 73.

[0042] As shown in Figure 3, the wiper carriage 71 supports two ink trays 73. The wiper carriage 71 is formed in a flat, plate-like shape along a horizontal plane. The two ink trays 73 are positioned on the upper surface of the wiper carriage 71. One of the two ink trays 73 supported by the wiper carriage 71 corresponds to the two recording heads 33 located on the left side of the three recording heads 33 included in the line head 31 (see Figure 2). The other of the two ink trays 73 supported by the wiper carriage 71 corresponds to the one recording head 33 located on the right side of the three recording heads 33 included in the line head 31 (see Figure 2). The ink trays 73 function as receptacles for the ink IN1 wiped away by the wiper 72.

[0043] The wiper 72 wipes away ink IN1 (see Figure 5) adhering to the nozzle surface 33A of the recording head 33. The wiper 72 is made of an elastic material such as rubber. The wiper 72 is a blade-shaped component. The wiper 72 is supported by a holder 72A (see Figure 5) provided on the upper surface of the ink tray 73.

[0044] The wipe unit 53 is provided to be movable between a second housing position and a wipe start position. Figure 1 shows the wipe unit 53 positioned at the second housing position. As shown in Figure 1, the second housing position is the position in which the wipe unit 53 is housed in the housing section 51. The wipe start position is the position in which the wipe unit 53 is positioned when the wiping process is started. The wipe start position is to the right of the second housing position. In other words, the wipe unit 53 is provided to be movable in the left-right direction D3. The wipe start position is also located between the image forming position and the retracted position.

[0045] Specifically, the four wiper carriages 71 of the wipe unit 53 are supported by the housing of the image forming apparatus 100 so as to be movable in the left-right direction D3. The four wiper carriages 71 move in the left-right direction D3 by receiving a driving force supplied from a drive unit (not shown).

[0046] In the image forming apparatus 100, when the wiping process is to be performed, the operating mode of the image forming apparatus 100 transitions from the image forming mode to a wiping mode in which the wiping process can be performed, in the following procedure. First, the head unit 21 is moved from the image forming position to the retracted position. Next, the wipe unit 53 is moved from the second housing position to the wipe start position. Then, the head unit 21 is moved downward from the retracted position until the nozzle surface 33A and the wiper 72 of the wipe unit 53 come into contact. This makes the wiping process executable.

[0047] Furthermore, the wipe unit 53 is provided so as to be movable between the wipe start position and the wipe end position. The wipe end position is the position of the wipe unit 53 when the wiping process is completed. The wipe end position is located behind the wipe start position. In other words, the wipe unit 53 moves in the front-rear direction D2 after being positioned at the wipe start position.

[0048] Specifically, the four wiper carriages 71 of the wipe unit 53 positioned at the wipe start position are supported by the housing of the image forming apparatus 100 so as to be movable in the front-rear direction D2. The four wiper carriages 71 move in the front-rear direction D2 by receiving driving force supplied from a drive unit (not shown).

[0049] The wiping process involves moving the four wiper carriages 71 from the wiping start position to the wiping end position. The wiping process causes the wiper 72 in contact with the nozzle surface 33A to move in the wiping direction D6 (see Figures 3 and 5). The wiping direction D6 is along the width direction D5 (see Figure 2). As a result, the ink IN1 adhering to the nozzle surface 33A is wiped off by the wiper 72. The ink IN1 wiped off by the wiper 72 moves to the ink tray 73 via the wiper 72 and the holder 72A.

[0050] Incidentally, a related technology is known for a liquid dispensing device that includes an imaging unit for imaging the nozzle surface 33A, and determines whether or not the nozzle 34 is in a defective state based on the imaging results from the imaging unit.

[0051] However, in the liquid dispensing device relating to the above-mentioned related technology, it is possible to detect a defective state of the nozzle 34 caused by foreign matter adhering to the nozzle 34, but it is not possible to detect a defective state of the nozzle 34 caused by the viscosity increase of the ink IN1 inside the nozzle 34.

[0052] In contrast, the image forming apparatus 100 according to an embodiment of the present invention can detect a defective state of the nozzle 34 caused by increased viscosity of the ink IN1 inside the nozzle, as described below.

[0053] The imaging unit 74 images the nozzle surface 33A after the ink IN1 has been wiped off by the wiper 72.

[0054] As shown in Figures 3 and 5, the imaging unit 74 is located upstream of the wiper 72 in the wiping direction D6. The imaging unit 74 includes an image sensor, such as an area CCD sensor, for imaging the nozzle surface 33A, a light source that emits light toward the nozzle surface 33A, and an optical system, such as an imaging lens, for forming an image of the light reflected from the nozzle surface 33A onto the image sensor. The imaging unit 74 is supported by a holder 72A (see Figure 5).

[0055] [Configuration of Control Unit 6] Next, the configuration of the control unit 6 will be described with reference to Figures 4 and 5.

[0056] As shown in Figure 4, the control unit 6 includes an acquisition processing unit 84, a determination processing unit 85, and a removal processing unit 86.

[0057] Specifically, the ROM 82 of the control unit 6 contains a defective nozzle detection program that enables the CPU 81 to function as one of the aforementioned processing units. The CPU 81 then executes the defective nozzle detection program stored in the ROM 82, thereby functioning as one of the aforementioned processing units.

[0058] The defective nozzle detection program may be recorded on a computer-readable recording medium such as a CD, DVD, or flash memory, and may be read from the recording medium and stored in a storage device such as the storage unit 5. Furthermore, some or all of the processing units included in the control unit 6 may be composed of electronic circuits. Also, the defective nozzle detection program may be a program that causes multiple processors to function as individual processing units included in the control unit 6.

[0059] The acquisition processing unit 84 acquires the amount of ink IN1 drawn out from inside the nozzle 34 to the nozzle surface 33A by the wiper 72, based on the imaging results from the imaging unit 74.

[0060] Specifically, the acquisition processing unit 84 acquires the amount of ink IN1 drawn out from inside the nozzle 34 onto the nozzle surface 33A for each nozzle 34.

[0061] As shown in Figure 5, the tip of the wiper 72, which moves along the wiping direction D6, comes into contact with the nozzle surface 33A and bites into the nozzle 34 as it passes through it. As a result, the ink IN1 inside the nozzle 34 adheres to the tip of the wiper 72 and is drawn out from inside the nozzle 34 to the nozzle surface 33A as the wiper 72 moves. Therefore, on the nozzle surface 33A, after the wiper 72 has passed the nozzle 34, the ink IN1 drawn out from the nozzle 34 adheres to the downstream side of the nozzle 34 in the wiping direction D6.

[0062] For example, the acquisition processing unit 84 detects an image in the captured image captured by the imaging unit 74 that shows the ink IN1 drawn out from the nozzle 34 by the wiper 72. For example, the acquisition processing unit 84 determines that a circular area of ​​the same color as the ink IN1, located downstream in the wiping direction D6 from the image showing the nozzle 34 in the captured image, is an image showing the ink IN1 drawn out from the nozzle 34. Then, based on the area of ​​the detected image showing the ink IN1, the acquisition processing unit 84 acquires the amount of ink IN1 drawn out from the nozzle 34 to the nozzle surface 33A.

[0063] The determination processing unit 85 determines that the nozzle 34 is in a defective state if the amount of ink IN1 acquired by the acquisition processing unit 84 is less than a predetermined first threshold (an example of a threshold according to the present invention).

[0064] Specifically, the determination processing unit 85 determines whether each nozzle 34 is in a defective state.

[0065] The higher the viscosity of the ink IN1 in the nozzle 34, the less ink IN1 is drawn out of the nozzle 34 when the wiper 72 passes through the nozzle 34. Therefore, the less ink IN1 is acquired by the acquisition processing unit 84, the higher the viscosity of the ink IN1 in the nozzle 34 can be determined.

[0066] For example, the determination processing unit 85 determines that the nozzle 34 is in a first defective state if the amount of ink IN1 acquired by the acquisition processing unit 84 is less than the first threshold and greater than or equal to a second threshold which is smaller than the first threshold. For example, the first defective state is a state in which the nozzle 34 cannot eject the target amount of ink IN1.

[0067] Furthermore, the determination processing unit 85 determines that the nozzle 34 is in a second defective state if the amount of ink IN1 acquired by the acquisition processing unit 84 is less than the second threshold. For example, the second defective state is a state in which ink IN1 cannot be ejected from the nozzle 34.

[0068] Furthermore, the determination processing unit 85 determines that the nozzle 34 is in a third defective state when it detects the foreign matter adhering to the nozzle 34 based on the captured image. For example, the third defective state is a state in which ink IN1 cannot be ejected from the nozzle 34, or the trajectory of the ejected ink IN1 is bent. For example, the foreign matter may be paper dust and dirt.

[0069] Furthermore, the determination processing unit 85 determines that the nozzle 34 is in a normal state if the amount of ink IN1 acquired by the acquisition processing unit 84 is equal to or greater than the first threshold, and no foreign matter adhering to the nozzle 34 is detected.

[0070] The removal processing unit 86 removes ink IN1 from the nozzle 34 if the determination processing unit 85 determines that the nozzle 34 is in a defective state.

[0071] Specifically, if the amount of ink IN1 acquired by the acquisition processing unit 84 is less than the first threshold, the removal processing unit 86 ejects an amount of ink IN1 from the nozzle 34 corresponding to the difference between that amount and the first threshold.

[0072] For example, the removal processing unit 86 executes a first purge process when it determines that any of the nozzles 34 included in the recording head 33 are in the third defective state. The first purge process is a process that ejects a predetermined first amount of ink IN1 from each of the nozzles 34 included in the recording head 33.

[0073] Furthermore, the removal processing unit 86 executes the first purging process if it determines that any of the nozzles 34 included in the recording head 33 are in the second defective state.

[0074] Furthermore, the removal processing unit 86 executes a second purge process if it is determined that none of the nozzles 34 included in the recording head 33 are in a faulty state other than the first faulty state, and if any of the nozzles 34 included in the recording head 33 are in the first faulty state. The second purge process is a process that ejects a second amount of ink IN1, which is less than the first amount, from each of the nozzles 34 included in the recording head 33.

[0075] The removal processing unit 86 may also remove the ink IN1 from the nozzle 34 using a suction unit capable of sucking the ink IN1 out of the nozzle 34.

[0076] [Defective nozzle detection process] The determination method of the present invention will be described below with reference to Figure 6, along with an example of the procedure for the defective nozzle detection process performed by the control unit 6 in the image forming apparatus 100. Here, steps S11, S12, etc. represent the numbers of the processing procedures (steps) performed by the control unit 6. The defective nozzle detection process is performed when a predetermined timing arrives, such as when the power to the image forming apparatus 100 is turned on. Furthermore, of the processes included in the defective nozzle detection process, all processes except for the process in step S12 are performed for each recording head 33.

[0077] <Step S11> First, in step S11, the control unit 6 performs a third purging process. The third purging process involves ejecting a third amount of ink IN1, which is less than the second amount, from each of the nozzles 34 included in the recording head 33, and adhering the ejected ink IN1 from each of the nozzles 34 to the nozzle surface 33A.

[0078] <Step S12> In step S12, the control unit 6 executes the wiping process.

[0079] <Step S13> In step S13, the control unit 6 uses the imaging unit 74 to image the nozzle surface 33A after the ink IN1 has been wiped off by the wiper 72 during the wiping process.

[0080] <Step S14> In step S14, the control unit 6 performs a first determination process to determine whether each nozzle 34 included in the recording head 33 is in the third defective state, based on the captured image obtained by the processing in step S13. The processing in step S14 is performed by the determination processing unit 85 of the control unit 6.

[0081] <Step S15> In step S15, the control unit 6 determines whether the first determination process has determined that any of the nozzles 34 included in the recording head 33 are in the third defective state.

[0082] Here, if the control unit 6 determines that any of the nozzles 34 included in the recording head 33 are in the third defective state (Yes side of S15), it moves the process to step S20. If none of the nozzles 34 included in the recording head 33 are determined to be in the third defective state (No side of S15), the control unit 6 moves the process to step S16.

[0083] <Step S16> In step S16, the control unit 6, based on the captured image obtained by the processing in step S13, obtains the amount of ink IN1 drawn out from inside the nozzle 34 to the nozzle surface 33A by the wiper 72 for each nozzle 34 included in the recording head 33. The processing in step S16 is an example of the acquisition step of the present invention and is performed by the acquisition processing unit 84 of the control unit 6.

[0084] <Step S17> In step S17, the control unit 6 performs a second determination process to determine whether each nozzle 34 included in the recording head 33 is in the first defective state or the second defective state, based on the results obtained from the processing in step S16. The processing in step S17 is an example of the determination step of the present invention and is performed by the determination processing unit 85 of the control unit 6.

[0085] <Step S18> In step S18, the control unit 6 determines whether the second determination process has determined that any of the nozzles 34 included in the recording head 33 are in the second defective state.

[0086] Here, if the control unit 6 determines that any of the nozzles 34 included in the recording head 33 are in the second defective state (Yes side of S18), it proceeds to step S20. If none of the nozzles 34 included in the recording head 33 are determined to be in the second defective state (No side of S18), the control unit 6 proceeds to step S19.

[0087] <Step S19> In step S19, the control unit 6 determines whether the second determination process has determined that any of the nozzles 34 included in the recording head 33 are in the first defective state.

[0088] Here, if the control unit 6 determines that any of the nozzles 34 included in the recording head 33 are in the first defective state (Yes side of S19), it proceeds to step S21. If none of the nozzles 34 included in the recording head 33 are determined to be in the first defective state (No side of S19), the control unit 6 terminates the defective nozzle detection process.

[0089] <Step S20> In step S20, the control unit 6 executes the first purging process. The process in step S20 is performed by the removal processing unit 86 of the control unit 6.

[0090] <Step S21> In step S21, the control unit 6 executes the second purging process. The process in step S21 is performed by the removal processing unit 86 of the control unit 6.

[0091] Furthermore, if the defective state of the nozzle 34 is not resolved even after executing the process in step S20 or step S21 a predetermined number of times, the control unit 6 may display a message to that effect on the operation display unit 4 and terminate the defective nozzle detection process.

[0092] In this way, the image forming apparatus 100 acquires the amount of ink IN1 drawn out from inside the nozzle 34 to the nozzle surface 33A by the wiper 72, based on the imaging result of the nozzle surface 33A after the ink IN1 has been wiped off by the wiper 72. If the acquired amount of ink IN1 is less than the first threshold, it is determined that the nozzle 34 is in a defective state. This makes it possible to detect a defective state of the nozzle 34 caused by the viscosity increase of the ink IN1 inside the nozzle 34.

[0093] Furthermore, in the image forming apparatus 100, if the amount of ink IN1 acquired by the acquisition processing unit 84 is less than the first threshold, an amount of ink IN1 corresponding to the difference between that amount and the first threshold is ejected from the nozzle 34. This makes it possible to increase the amount of ink IN1 ejected from the nozzle 34 the higher the viscosity of the ink IN1 in the nozzle 34.

[0094] Furthermore, in the image forming apparatus 100, the imaging unit 74 is provided on a holder 72A that supports the wiper 72. In other words, the imaging unit 74 is provided so as to be movable together with the wiper 72. This simplifies the configuration of the image forming apparatus 100 compared to a configuration in which the imaging unit 74 is provided so as to be movable separately from the wiper 72.

[0095] The nozzle surface 33A may include one or more nozzle groups composed of multiple nozzles 34. For example, the nozzle surface 33A may be divided into multiple partitioned regions, and the multiple nozzles 34 included in the partitioned regions may be considered the nozzle group. In this case, the removal processing unit 86 may remove ink IN1 from each of the nozzles 34 determined to be in a defective state by the determination processing unit 85 and from each of the nozzles 34 belonging to the same nozzle group as the defective nozzle 34. In other words, ink IN1 does not need to be removed from each of the nozzles 34 belonging to the nozzle group that does not include the defective nozzle 34.

[0096] Alternatively, the removal processing unit 86 may remove ink IN1 only from the nozzles 34 that have been determined to be in a defective state by the determination processing unit 85.

[0097] [Notes on the invention] The following is an overview of the invention extracted from the above-described embodiments. Note that each configuration and processing function described below can be selected and combined as desired.

[0098] <Note 1> A liquid dispensing device comprising: a dispensing unit having a nozzle surface on which a nozzle is formed and dispensing liquid from the nozzle; a wiper for wiping off the liquid adhering to the nozzle surface; an imaging unit for imaging the nozzle surface after the liquid has been wiped off by the wiper; an acquisition processing unit for acquiring the amount of liquid drawn from inside the nozzle to the nozzle surface by the wiper based on the imaging results from the imaging unit; and a determination processing unit for determining that the nozzle is in a defective state if the amount of liquid acquired by the acquisition processing unit is less than a predetermined threshold.

[0099] <Note 2> The liquid dispensing device according to Appendix 1, further comprising a removal processing unit that removes the liquid from the nozzle when the determination processing unit determines that the nozzle is in a defective state.

[0100] <Note 3> The removal processing unit discharges an amount of the liquid from the nozzle corresponding to the difference between the amount obtained by the acquisition processing unit and the threshold when the amount of the liquid obtained by the acquisition processing unit is less than the threshold, as described in Appendix 2.

[0101] <Note 4> The liquid dispensing device according to Appendix 2 or 3, wherein the nozzle surface includes a group of nozzles composed of a plurality of nozzles, the acquisition processing unit acquires the amount of liquid drawn from inside each nozzle to the nozzle surface, the determination processing unit determines whether each nozzle is in a defective state, and the removal processing unit removes the liquid from each of the nozzles determined to be in a defective state by the determination processing unit and from each of the nozzles belonging to the same group of nozzles as the nozzle in question.

[0102] <Note 5> The liquid dispensing device according to any one of the appendices 1 to 4, wherein the nozzle surface includes a plurality of nozzles arranged along a predetermined specific direction, the wiper is provided to be movable along the specific direction, and the imaging unit is provided to be movable integrally with the wiper.

[0103] <Note 6> A determination method performed in a liquid dispensing device comprising: a dispensing unit having a nozzle surface on which a nozzle is formed and dispensing liquid from the nozzle; a wiper for wiping off the liquid adhering to the nozzle surface; and an imaging unit for imaging the nozzle surface after the liquid has been wiped off by the wiper, the determination method comprising: an acquisition step of acquiring the amount of liquid drawn from inside the nozzle to the nozzle surface by the wiper based on the imaging result from the imaging unit; and a determination step of determining that the nozzle is in a defective state if the amount of liquid acquired in the acquisition step is less than a predetermined threshold. [Explanation of Symbols]

[0104] 1 Paper feed section 2 Image forming unit 3. Maintenance Department 4 Operation display section 5 Storage section 6 Control Unit 21 Head Unit 22 Conveyor Units 31 Line Head 32 Support part 33 Recording head 33A Nozzle surface 34 nozzles 51 Storage Unit 52 Cap Unit 53 wipe units 71 Wiper Carriage 72 Wiper 73 Ink Tray 74 Imaging Unit 81 CPU 82 ROM 83 RAM 84 Acquisition Processing Unit 85. Determination Processing Unit 86 Removal Processing Unit 100 Image forming apparatus

Claims

1. A discharge section having a nozzle surface on which a nozzle is formed, and which discharges liquid from the nozzle, A wiper for wiping off the liquid adhering to the nozzle surface, An imaging unit that images the nozzle surface after the liquid has been wiped away by the wiper, An acquisition processing unit acquires the amount of liquid drawn out from inside the nozzle to the nozzle surface by the wiper based on the imaging results from the imaging unit, A determination processing unit determines that the nozzle is in a defective state when the amount of liquid acquired by the acquisition processing unit is less than a predetermined threshold, A liquid dispensing device equipped with the following features.

2. If the determination processing unit determines that the nozzle is in a defective state, the system includes a removal processing unit that removes the liquid from the nozzle. The liquid dispensing device according to claim 1.

3. The removal processing unit, when the amount of liquid acquired by the acquisition processing unit is less than the threshold, discharges an amount of the liquid from the nozzle corresponding to the difference between the amount and the threshold. The liquid dispensing device according to claim 2.

4. The nozzle surface includes a group of nozzles composed of a plurality of the nozzles, The acquisition processing unit acquires the amount of liquid drawn out from inside the nozzle to the nozzle surface for each nozzle, The determination processing unit determines whether each nozzle is in a defective state, The removal processing unit removes the liquid from each of the nozzles that the determination processing unit has determined to be in a defective state and from each of the nozzles belonging to the same group of nozzles as the said nozzle. The liquid dispensing device according to claim 2 or 3.

5. The nozzle surface includes a plurality of nozzles arranged along a predetermined specific direction, The wiper is provided so as to be movable along the specific direction, The imaging unit is provided so as to be movable together with the wiper. The liquid dispensing device according to claim 1 or 2.

6. A determination method performed by a liquid dispensing device comprising: a dispensing unit having a nozzle surface on which a nozzle is formed and dispensing liquid from the nozzle; a wiper for wiping off the liquid adhering to the nozzle surface; and an imaging unit for imaging the nozzle surface after the liquid has been wiped off by the wiper, Based on the imaging results from the imaging unit, the acquisition step is to acquire the amount of liquid drawn out from inside the nozzle to the nozzle surface by the wiper, A determination step in which the nozzle is determined to be in a defective state if the amount of liquid obtained by the acquisition step is less than a predetermined threshold, A determination method that includes this.

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