Ink liquid surface height measurement device and image formation device

Abstract

To accurately measure a liquid surface height of ink, using a hall element, even when aging variation occurs.SOLUTION: An ink liquid surface height measurement device for measuring a liquid surface height of ink in a container includes: a float which has a magnet and is moved accompanied by change of the liquid surface height; a hall element for detecting the change of magnetic flux density by the magnet moved together with the float as a continuous value; an adjustment part for adjusting the liquid surface height to a reference height; and a correction part for acquiring the output value of the hall element when the liquid surface height is the reference height, and correcting the liquid surface height, on the basis of the output value.SELECTED DRAWING: Figure 4B

Description

[Technical Field]

[0001] The present invention relates to an ink level measuring device and an image forming apparatus. [Background technology]

[0002] In an inkjet image forming apparatus, a tank that stores ink to be supplied to an inkjet head is provided with an ink level measuring device that measures the ink level in the tank.

[0003] In the invention disclosed in Patent Document 1, an ink level measuring device measures the upper and lower limits of the ink level to detect abnormalities in parts of an ink supply device that supplies ink to a tank. The ink level measured by the ink level measuring device is not a continuous value but a discrete value between the upper and lower limits, and the ink level between the upper and lower limits is unknown. Therefore, it is difficult to detect abnormalities in parts of the ink supply device other than the upper and lower limits, or even if it is possible to detect an abnormality, the detection accuracy is insufficient.

[0004] The invention disclosed in Patent Document 2 discloses an ink level measuring device that uses a capacitance sensor to continuously measure changes in the ink level in a tank. However, capacitance sensors have the problem of not being sensitive enough depending on the physical properties of the ink. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-783 [Patent Document 2] Japanese Patent Publication No. 2020-34485 Summary of the Invention [Problem to be solved by the invention]

[0006] The inventions disclosed in Patent Documents 1 and 2 have the problems described above. Therefore, the present inventors investigated a method using a Hall element as a method for continuously measuring changes in the ink level, regardless of the ink's physical properties. In order to accurately detect abnormalities in ink supply device components, it is necessary to measure minute changes in the ink level, but Hall elements have the characteristic of causing output values ​​to change (drift) over time.

[0007] SUMMARY OF THE INVENTION An object of the present invention is to provide an ink level measuring device and an image forming apparatus that can measure the ink level with high accuracy using a Hall element even if there is a change over time. [Means for solving the problem]

[0008] The ink level measuring device according to the present invention comprises: An ink level measuring device for measuring the ink level in a container, a float having a magnet and moving in accordance with the change in the liquid level; a Hall element that detects, as a continuous value, a change in magnetic flux density caused by the magnet that moves together with the float; an adjusting unit that adjusts the liquid level to a reference height; a correction unit that acquires an output value of the Hall element when the liquid level is at the reference level, and corrects the liquid level based on the output value; Equipped with.

[0009] The image forming apparatus according to the present invention comprises: a container for storing ink; an image forming unit that forms an image using the ink supplied from the container; The ink liquid level measuring device; Equipped with. [Effects of the Invention]

[0010] According to the present invention, the ink level can be measured with high accuracy using a Hall element, even if there is a change over time. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus and an ink liquid level measuring device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the main parts of a control system of the image forming apparatus shown in FIG. [Figure 3] FIG. 3 is a flowchart illustrating the zero point correction of the Hall sensor of the ink level measuring device. [Figure 4A] FIG. 4A is a graph showing the relationship between the liquid level and the sensor output value before zero point correction. [Figure 4B] FIG. 4B is a graph showing the relationship between the liquid level and the sensor output value after zero point correction. [Figure 5A] FIG. 5A is a diagram showing the relationship between the amount of zero point drift and the deviation of the measurement value when no zero point correction is performed. [Figure 5B] FIG. 5B is a diagram showing the relationship between the amount of zero point drift and the deviation of the measurement value when zero point correction is performed. [Figure 6] FIG. 6 is a flowchart illustrating the full-area correction of the Hall sensor of the ink level measuring device. [Figure 7A] FIG. 7A is a diagram showing the initial state of the first and second sub-tanks in the full-area correction described with reference to FIG. [Figure 7B] FIG. 7B is a diagram showing a state in which the liquid levels in the first sub-tank and the second sub-tank are aligned in the full-area correction described with reference to FIG. [Figure 7C] FIG. 7C is a diagram showing a state in which the first sub-tank is sealed in the full-area correction described with reference to FIG. [Figure 7D] FIG. 7D is a diagram showing a state in which ink is being sent from the first sub-tank to the second sub-tank in the full-area correction described with reference to FIG. [Figure 8A] FIG. 8A is a diagram illustrating the relationship between the liquid level of the second sub-tank and the sensor output value relative to the pressure value of the first sub-tank in the full-range correction described in FIG. [Figure 8B]FIG. 8B is a graph showing the relationship between the sensor output value and the liquid level obtained from the relationship shown in FIG. 8A. [Figure 9] FIG. 9 is a graph showing the relationship between pump drive time and liquid level height, from when the ink supply unit is brand new to when it is determined to be faulty. [Figure 10] FIG. 10 is a graph illustrating the results of determination based on the change over time in the amount of ink fed over a predetermined period of time. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0013] [Image forming equipment] Fig. 1 is a schematic diagram illustrating an example of an inkjet printer 100 (image forming apparatus of the present invention) according to this embodiment and an ink liquid level measuring device 440. Fig. 2 is a block diagram showing the main parts of a control system of the inkjet printer 100 shown in Fig. 1.

[0014] As shown in FIG. 2, the inkjet printer 100 includes a conveying section 10, a supplying section 20, a discharging section 30, an ink supplying section 40, a head module 50 (the image forming section in the present invention), an operation display section 70, an input / output interface 80, a control section 90, and the like.

[0015] The conveying unit 10 conveys the recording medium M (see FIG. 1). The conveying unit 10 is composed of, for example, a conveying belt or a conveying drum. The recording medium M supplied from the supplying unit 20 is conveyed to the head module 50 by the conveying operation of the conveying unit 10. Thereafter, the recording medium M on which an image has been formed by the head module 50 is conveyed to the discharge unit 30 by the conveying operation of the conveying unit 10.

[0016] The recording medium M can be any of various media capable of fixing ink ejected from an inkjet head (not shown) of the head module 50. The recording medium M is, for example, a medium such as sheet-shaped paper, cloth (woven fabric), or resin. Note that the recording medium M is not limited to a sheet-shaped medium, and may also be a medium such as roll-shaped paper, cloth, or resin.

[0017] The supply unit 20 stores the recording medium M and supplies the recording medium M to the transport unit 10. The supply unit 20 has, for example, a storage unit that stores the recording medium M, and has a belt, rollers, etc. that transport the recording medium M to the transport unit 10.

[0018] The discharge unit 30 stores the recording medium M discharged from the conveyance unit 10. The discharge unit 30 has, for example, a belt or rollers that transport the recording medium M from the conveyance unit 10, and has a storage unit that stores the recording medium M.

[0019] The ink supply unit 40 is a device that supplies ink I to the head module 50. The ink supply unit 40 has a first sub-tank unit 410, a liquid delivery unit 420, a second sub-tank unit 430, an ink liquid level measuring device 440, and the like.

[0020] The first sub-tank portion 410 stores the ink I to be sent to the second sub-tank portion 430. The first sub-tank portion 410 has a first sub-tank 411 (supply source container in the present invention) that stores the ink I, and the like. The first sub-tank 411 is connected to a main tank (not shown) that stores the ink I via a liquid sending path (not shown). The ink I stored in the main tank is sent to the first sub-tank 411 using a pump or the like (not shown).

[0021] The first sub-tank unit 410 also has a float 412, a guide unit 413, a magnet 414, and a reed switch 416 as a reference height detection unit D1 that detects whether the liquid level of the ink I in the first sub-tank 411 is at a reference height.

[0022] The float 412 is a floating body that floats on the surface of the ink I. In a plan view, a through hole into which the guide part 413 is inserted is formed in the center of the float 412.

[0023] The guide portion 413 is a rod-shaped member that extends downward and has an end supported on the top plate side of the first sub-tank 411. The guide portion 413 is inserted into a through-hole in the float 412. The guide portion 413 prevents the float 412 from tilting, and guides the float 412 so that it can move vertically, i.e., move up and down, in the direction of the liquid level. Therefore, the float 412 moves up and down along the guide portion 413 in accordance with the up and down movement of the liquid level of the ink I.

[0024] Note that the guide portion 413 may be a rod-shaped member whose end is supported on the bottom plate side of the first sub-tank 411 and extends upward, as long as it can prevent the float 412 from tilting and can guide the float 412 so that it can move up and down. Also, as long as it can prevent the float 412 from tilting, the guide portion 413 and the through-hole in the float 412 may be omitted. For example, if the outer peripheral side surface of the float 412 is formed close to the inner wall of the first sub-tank 411, the inner wall of the first sub-tank 411 will prevent the float 412 from tilting and will function as a guide portion that guides the float 412 so that it can move up and down.

[0025] A permanent magnet 414 is disposed inside the float 412. The magnet 414 is, for example, an annular body with a rectangular cross section. The magnet 414 is disposed inside the float 412 at a position that maintains balance so that the float 412, which floats on the surface of the ink I, does not tilt.

[0026] The reed switch 416 is a sensor that detects whether the liquid level of the ink I in the first subtank 411 is at a reference height, and is positioned at that reference height. The reed switch 416 is a magnetic switch that turns on or off by magnetic force, and is turned on by the magnetic force of the magnet 414 in the float 412 when the liquid level of the ink I is at the reference height, and is turned off at all other times.

[0027] In this way, in the first sub-tank unit 410, the reference height detection unit D1 detects whether the liquid level of the ink I in the first sub-tank 411 is at the reference height. Note that, although a float-type level switch is exemplified as the reference height detection unit D1 here, other types, such as a capacitance-type level switch, may also be used.

[0028] The first sub-tank unit 410 also has a valve 417 that seals the upper space of the first sub-tank 411 or opens it to the atmosphere, and a pressure sensor 418 that detects the pressure inside the first sub-tank 411. The valve 417 and the pressure sensor 418 are used for correction, which will be described later.

[0029] The liquid sending unit 420 sends the ink I stored in the first sub-tank 411 to the second sub-tank unit 430 (second sub-tank 431 described later). The liquid sending unit 420 has a tank supply path 421 (ink supply path in the present invention), a degassing module 422, a liquid sending pump 423, a liquid sending valve 424, etc.

[0030] The tank supply path 421 connects the first sub-tank 411 and the second sub-tank 431, and serves as a flow path from the first sub-tank 411 to the second sub-tank 431. The degassing module 422 has a filter 425. The degassing module 422 degasses the ink I to be delivered, and then filters the ink I using the filter 425.

[0031] The liquid feed pump 423 is a pump that feeds the ink I from the first sub-tank 411 to the second sub-tank 431. The liquid feed valve 424 opens and closes the tank supply path 421. For example, when feeding the ink I from the first sub-tank 411 to the second sub-tank 431, the liquid feed valve 424 opens, and when feeding the ink I from the second sub-tank 431 to the head module 50, the liquid feed valve 424 closes.

[0032] The second sub-tank unit 430 stores the ink I to be sent to the head module 50. The second sub-tank unit 430 includes a second sub-tank 431 (a container in the present invention) that stores the ink I, an air pressure pump 432, a head supply path 433, an ink liquid level measuring device 440, and the like.

[0033] The second sub-tank 431 is connected to the first sub-tank 411 via a tank supply path 421 , and is connected to the head module 50 via a head supply path 433 .

[0034] The air pressure pump 432 is connected to the upper part of the second sub-tank 431, and controls the pressure in the upper space of the second sub-tank 431 to a desired pressure. The head supply path 433 connects the lower part of the second sub-tank 431 to the head module 50, and supplies ink I from the second sub-tank 431 to the head module 50.

[0035] The second sub-tank portion 430 described above is provided with an ink level measuring device 440 that measures the level of the ink I in the second sub-tank 431. An ink level measuring device 440 may also be provided in the first sub-tank portion 410 to measure the level of the ink I in the first sub-tank 411. The ink level measuring device 440 will be described later.

[0036] The head module 50 has devices and components necessary for image formation, such as an inkjet head, etc. The head module 50 ejects ink I supplied from the ink supply unit 40 (second sub-tank unit 430) from the nozzles of the inkjet head to form an image on the recording medium M.

[0037] 1, for simplicity, the ink supply units 40 and head modules 50 for one color are shown, but the ink supply units 40 and head modules 50 are arranged according to the number of colors to be used. For example, when four colors, yellow (Y), magenta (M), cyan (C), and black (K), are used, ink supply units 40 and head modules 50 for four colors are arranged.

[0038] The operation display unit 70 is, for example, a flat panel display such as a liquid crystal display with a touch panel or an organic EL (Electro Luminescence) display. The operation display unit 70 displays an operation menu for the user, information related to image data, various states of the inkjet printer 100, etc. The operation display unit 70 also has a plurality of keys and accepts various input operations from the user.

[0039] The input / output interface 80 mediates the transmission and reception of data between the external device 200 and the control unit 90. The input / output interface 80 is configured, for example, by any one of various serial interfaces, various parallel interfaces, or a combination of these.

[0040] The external device 200 is, for example, a personal computer or a facsimile machine, and supplies print jobs, image data, and the like to the control unit 90 via the input / output interface 80 .

[0041] As shown in FIG. 2, the control unit 90 includes a CPU (Central Processing Unit) 91, a RAM (Random Access Memory) 92, a ROM (Read Only Memory) 93, a storage unit 94, and the like.

[0042] The CPU 91 reads out various control programs and setting data stored in the ROM 93, stores them in the RAM 92, and executes the programs to perform various arithmetic processing. For example, the control unit 90 generates a drive signal for an image to be formed based on image data received from the input / output interface 80, and outputs the drive signal to the inkjet head.

[0043] The RAM 92 provides a working memory space for the CPU 91 and stores temporary data. The RAM 92 may include a non-volatile memory.

[0044] The ROM 93 stores various control programs and setting data executed by the CPU 91. Note that, instead of the ROM 93, a rewritable non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used.

[0045] The storage unit 94 stores print jobs and image data related to the print jobs input from the external device 200 via the input / output interface 80. As the storage unit 94, for example, a hard disk drive (HDD) or a solid state drive (SSD) is used, and a dynamic random access memory (DRAM) or the like may also be used in combination.

[0046] The control unit 90 is connected to the transport unit 10, supply unit 20, discharge unit 30, ink supply unit 40, head module 50, operation and display unit 70, input / output interface 80, etc. The control unit 90 controls the overall operation of the inkjet printer 100. The transport unit 10, supply unit 20, discharge unit 30, ink supply unit 40, head module 50, operation and display unit 70, input / output interface 80, etc. are controlled by the control unit 90 to execute predetermined processes.

[0047] With the above configuration, the inkjet printer 100 supplies the recording medium M from the supply section 20 to the conveying section 10, forms an image on the recording medium M conveyed to the conveying section 10 using the head module 50, and conveys the recording medium M with the image formed thereon to the discharge section 30.

[0048] [Ink level measuring device] 1, an ink level measuring device 440 is provided in the second sub-tank unit 430 of the ink supply unit 40. The ink level measuring device 440 includes a float 441, a guide unit 442, a magnet 443, a reed switch 445, a hall sensor 446, a magnetic body 447, a measurement control unit 448, and the like.

[0049] The second sub-tank unit 430 has a float 441, a guide unit 442, a magnet 443, and a reed switch 445 as a reference height detection unit D2 that detects whether the liquid level of the ink I in the second sub-tank 431 is at the reference height.

[0050] The float 441, guide 442, magnet 443, and reed switch 445 have the same configuration as the float 412, guide 413, magnet 414, and reed switch 416 in the reference height detection unit D1, and a redundant description thereof will be omitted here. Here, the guide 442 restricts the horizontal movement of the float 441 so that the position of the magnet 443 relative to the Hall sensor 446 does not change in the horizontal direction along the liquid surface.

[0051] In the second sub-tank unit 430, the reference height detection unit D2 detects whether the liquid level of the ink I in the second sub-tank 431 is at the reference height. Note that although a float-type level switch is exemplified as the reference height detection unit D2 here as well, other types, such as a capacitance-type level switch, may also be used.

[0052] The Hall sensor 446 is a magnetic sensor that uses a Hall element to detect the strength of a magnetic field, and may include an operational amplifier circuit or the like.

[0053] The Hall sensor 446 is disposed in a position where it can measure the change in magnetic flux density caused by the magnet 443 that moves up and down together with the float 441, preferably in a position where the magnetic flux density is large. For example, the Hall sensor 446 is fixed to the top plate side of the second subtank 431 together with the magnetic body 447, and disposed in a position facing the magnet 443 in the vertical direction.

[0054] With the above-described configuration, the Hall sensor 446 detects the change in magnetic flux density, which is a change in physical quantity accompanying a change in the liquid level, as a continuous value, and outputs the sensor output value.

[0055] The magnetic body 447 is made of a material with high magnetic permeability, such as iron, for example, SS400, a rolled steel material for general structural use. Normally, a magnetic field is distorted toward a material with high magnetic permeability, such as a magnetic body, causing magnetic flux to concentrate. Therefore, by placing the magnetic body 447 close to the Hall sensor 446, the magnetic flux from the magnet 443 can be concentrated at the position of the Hall sensor 446, thereby increasing the magnetic flux density.

[0056] In particular, when the magnet 443 is disposed below the Hall sensor 446, the magnetic flux density at the sensor position is increased by disposing the magnetic body 447 closer to the upper side of the housing of the Hall sensor 446. Therefore, in Fig. 1, as an example, the magnetic body 447 is disposed on the upper surface of the housing of the Hall sensor 446. Furthermore, the larger the size (width, thickness, and depth) of the magnetic body 447, the greater the magnetic flux density at the sensor position.

[0057] The Hall sensor 446 has the magnetic body 447 disposed close to the upper side of its housing, so it can detect the ink I level, i.e., the magnetic flux density that changes with the up and down movement of the float 441, as a continuous value with high sensitivity, and output a value corresponding to the ink level. As a result, the ink level measuring device 440 can measure the ink I level continuously and with high accuracy.

[0058] The Hall sensor 446 and the magnetic body 447 may be fixed to the bottom plate side of the second sub-tank 431 and disposed in a position facing the magnet 443 in the vertical direction. In this case, it is desirable to dispose the magnetic body 447 on the lower surface of the housing of the Hall sensor 446.

[0059] Although not shown, the measurement control unit 448 includes a CPU, RAM, ROM, a storage unit, etc. The CPU reads out programs and data stored in the ROM, stores them in the RAM, and executes the programs to perform various processes. For example, the measurement control unit 448 determines the liquid level based on the output value from the Hall sensor 446.

[0060] Incidentally, as described above, the Hall element used in the Hall sensor 446 has a characteristic that the output value changes (drifts) over time.

[0061] Therefore, in this embodiment, in order to accurately measure the liquid level of ink I using a Hall sensor 446 having a Hall element even if there is a change over time, the ink liquid level measuring device 440 has the configuration described below.

[0062] Specifically, the ink level measuring device 440 includes an adjustment unit that adjusts the level of the ink I to a reference height, and a correction unit that corrects the level based on the output of the Hall sensor 446 when the level is at the reference height. The adjustment unit and the correction unit are provided as functions of the measurement control unit 448, and are provided as programs executed by the measurement control unit 448, for example.

[0063] [Correction 1] Correction 1 (zero point correction), which is an example of correction using the adjustment unit and correction unit, will be described with reference to Fig. 1 and Fig. 3. Fig. 3 is a flowchart explaining zero point correction of the Hall sensor 446 of the ink level height measuring device 440. Here, correction is performed at the zero point, i.e., the lower limit, so the reference height in the reference height detection unit D2 is set to the lower limit of the second sub-tank 431.

[0064] In the inkjet printer 100, when an image is formed on the recording medium M by a print job, the ink I in the second subtank 431 is consumed, and the liquid level of the ink I in the second subtank 431 falls below the reference height (lower limit). The zero point correction described below is thus executed when the liquid level of the ink I in the second subtank 431 falls below the reference height (lower limit) during image formation by a print job.

[0065] (Step S11) The measurement control unit 448 (adjustment unit) uses the reference height detection unit D2 to check whether the liquid level of the ink I in the second sub-tank 431 is below the reference height. If the liquid level of the ink I in the second sub-tank 431 is below the reference height (YES), the process proceeds to step S12, and if the liquid level of the ink I in the second sub-tank 431 is not below the reference height (NO), the process repeats step S11.

[0066] (Step S12) The measurement control unit 448 (adjustment unit) turns on the liquid feed pump 423 (also opens the liquid feed valve 424) to feed the ink I from the first sub-tank 411 to the second sub-tank 431.

[0067] (Step S13) The measurement control unit 448 (adjustment unit) uses the reference height detection unit D2 to check whether the liquid level of the ink I in the second sub-tank 431 is at the reference height. If the liquid level of the ink I in the second sub-tank 431 is at the reference height (YES), the process proceeds to step S14, and if the liquid level of the ink I in the second sub-tank 431 is not below the reference height (NO), steps S12 and S13 are repeated.

[0068] (Step S14) The measurement control unit 448 (adjustment unit) turns off the liquid supply pump 423 (also closes the liquid supply valve 424) and stops the supply of ink I from the first sub-tank 411 to the second sub-tank 431. In other words, when the liquid level of ink I in the second sub-tank 431 reaches the reference height, the supply of ink I is stopped.

[0069] (Step S15) The measurement control unit 448 (correction unit) acquires the output value of the Hall sensor 446 using the ink level measurement device 440 when the level of the ink I in the second sub-tank 431 is at the reference height.

[0070] Then, the measurement control unit 448 (correction unit) corrects the liquid level in the following manner based on the output value of the Hall sensor 446 when the liquid level of the ink I is at the reference height.

[0071] As an example, it is assumed that the liquid level L is calculated based on the output value V of the Hall sensor 446 by the following calculation formula (1).

[0072] L = a × V + b (1)

[0073] In the above formula (linear equation), coefficient a is a predetermined coefficient and is the slope of the formula. Coefficient b is also a predetermined coefficient and is the intercept of the formula, but here, by correcting coefficient b, which is a constant term, the Hall sensor 446 is used to measure the ink I liquid level with high accuracy even if there is a change over time.

[0074] Specifically, the above steps S11 to S15 are executed when the ink level measuring device 440 starts to be used (initial stage).Then, the output value V of the Hall sensor 446 when the level of the ink I in the second sub-tank 431 is at the reference height is acquired as the initial value b0.

[0075] Thereafter, for example, when the liquid level of the ink I in the second subtank 431 falls below the reference height, the above steps S11 to S15 are executed. Then, by performing the above steps S11 to S15, the output value V of the Hall sensor 446 when the liquid level of the ink I in the second subtank 431 is at the reference height is acquired as the current value bt. The difference Δb between the initial value b0 and the current value bt is calculated as a correction value for the coefficient b, and the measurement control unit 448 calculates the liquid level L from the output value V of the Hall sensor 446 using the following calculation formula (2) that adds the difference Δb as a correction term for the coefficient b. Using this calculation formula (2), the liquid level of the ink I can be measured accurately using the Hall sensor 446, even if there is a change over time.

[0076] L=a×V+(b+Δb)=a×V+(b+b0-bt) ··· (2)

[0077] Here, we have shown an example in which the relationship between the liquid level height L and the output value V of the Hall sensor 446 is a linear equation, but even if this relationship is an n-th order equation of second or higher order, the constant term (intercept) can be corrected in the same way as in a linear equation.

[0078] Fig. 4A is a graph showing the relationship between the liquid level L before zero point correction and the output value V of the Hall sensor 446. Fig. 4B is a graph showing the relationship between the liquid level L after zero point correction and the output value V of the Hall sensor 446. Note that the graphs in Fig. 4A and 4B show, as an example, a case where the relationship between the liquid level L and the output value V of the Hall sensor 446 is a quadratic equation.

[0079] As described above, the Hall element used in the Hall sensor 446 has a characteristic that its output value changes (drifts) over time. For example, in Fig. 4A, graph F0 is a graph showing the relationship between the liquid level L at the start (initial stage) of use of the ink level measurement device 440 and the output value V of the Hall sensor 446. When the ink level measurement device 440 is used over a long period of time, the output value V of the Hall sensor 446 relative to the liquid level L may drift significantly (see graph Fb) or slightly (see graph Fs) from graph F0, depending on, for example, the usage environment.

[0080] As shown in FIG. 4A, when the output value V of the Hall sensor 446 drifts from the initial graph F0 to graphs Fb and Fs, for example, even if the output value V is the same, V=V1, the liquid level L is obtained as a liquid level indicated in the range of L0 to L1, and the accuracy of obtaining the liquid level is not high.

[0081] Therefore, in this embodiment, the correction amount Δb is calculated using the current value bt obtained in steps S11 to S15 to align (match) the zero points of the graphs Fb and Fs with the zero point of the initial graph F0, and zero point correction is performed. As shown in Fig. 4B, graphs Fbc and Fsc are graphs obtained by zero point correction of the graphs Fb and Fs, respectively.

[0082] As a result, as shown in FIG. 4B, even when the output value V is the same, for example, V1, the liquid level L is obtained as a liquid level indicated in the range of L0 to L2, which is narrower than the range of L0 to L1, and the accuracy of obtaining the liquid level is improved.

[0083] Furthermore, at a liquid level close to the zero point (lower limit), as shown in FIG. 4B, the amount of drift of the graphs Fbc and Fsc relative to the graph F0 becomes small, so the accuracy of determining the liquid level becomes even better.

[0084] Here, the reference height is set to the lower limit of the second sub-tank 431, so this is called zero point correction, but the above-mentioned correction may also be performed by setting a known height such as the middle position or upper limit of the second sub-tank 431 as the reference height.

[0085] 5A and 5B are graphs comparing the effects of the above-mentioned zero point correction. Fig. 5A shows the relationship between the amount of zero point drift and the deviation of the measurement value when there is no zero point correction. Fig. 5B shows the relationship between the amount of zero point drift and the deviation of the measurement value when there is zero point correction.

[0086] Here, a sensor with a specification of ±0.5% for zero point drift due to changes over time is used as the Hall sensor 446, and the target value (target accuracy) for the deviation of the measurement value is ±1.5 mm.

[0087] Using this Hall sensor 446, the zero-point drift amount (%) and the deviation of the measurement value (mm) were measured over a predetermined period without zero-point correction, and the results shown in FIG. 5A were obtained. During this period, the zero-point drift amount did not drift to near 0.5% or -0.5%. When the obtained results were linearly approximated to predict the deviation of the measurement value at 0.5% and -0.5%, the deviation was 1.5 mm at 0.5% and -2.5 mm at -0.5%, which did not meet the target deviation of the measurement value of ±1.5 mm.

[0088] In contrast, when the zero-point drift amount (%) and the deviation of the measurement value (mm) were measured over a specified period with zero-point correction, the results shown in Figure 5B were obtained. Even during this period, the zero-point drift amount did not drift to near 0.5% or -0.5%. When the obtained results were linearly approximated to predict the deviation of the measurement value at 0.5% and -0.5%, the deviation was 0.73 mm at 0.5% and -0.95 mm at -0.5%, which satisfied the target deviation of the measurement value of ±1.5 mm.

[0089] By performing zero point correction in this way, even if there is a change over time, the Hall sensor 446 can be used with a target accuracy of ±1.5 mm, and the liquid level can be measured with high accuracy.

[0090] As described above, in this embodiment, the inkjet printer 100 includes the ink level measuring device 440. The ink level measuring device 440 includes an adjustment unit that adjusts the ink level to a reference height, and a correction unit that corrects the ink level based on the output of the Hall sensor 446 when the ink level is at the reference height.

[0091] According to this embodiment configured as described above, the ink level is corrected based on the output of the Hall sensor 446 when the ink level is at the reference height. Therefore, even if there is a change over time, the ink level can be measured with high accuracy using the Hall sensor 446.

[0092] Furthermore, as described above, the ink level measuring device 440 has the Hall sensor 446 provided with the magnetic body 447 in its housing, so that the ink level can be measured with even higher accuracy.

[0093] [Correction 2] Another example of correction, correction 2 (full range correction), will be described with reference to FIG. 1 as well as FIGS. 6 to 7D.

[0094] In the above-described correction 1, in consideration of the case where the difference Δb between the initial value b0 and the current value bt becomes equal to or greater than a predetermined value, the ink level measurement device 440 may further include an acquisition unit that acquires a relational expression for correcting the liquid level over the entire range of liquid level heights. The acquisition unit is also provided as a function of the measurement control unit 448, and is provided as, for example, a program executed by the measurement control unit 448. Here, the correction unit corrects the liquid level height using the relational expression acquired by the acquisition unit.

[0095] Here, as an example, when the difference Δb becomes 0.5% (predetermined value) or more with respect to the initial value b0, that is, when Δb / b0×100=(b0-bt) / b0×100≧0.5, the acquisition unit acquires a relational expression that enables full-area correction.

[0096] 4A and 4B, the drift of the sensor output value of the Hall sensor 446 includes changes in the vertical axis direction and changes in the inclination. When the change in the vertical axis direction, i.e., the above-mentioned difference Δb, becomes larger than a predetermined value, the change in the inclination affects the measurement accuracy of the liquid level height of the ink I, so the acquisition unit acquires a relational expression that allows for full-range correction.

[0097] FIG. 6 is a flowchart illustrating the full-range correction of the Hall sensor 446 of the ink level height measuring device 440. FIG. 7A is a diagram illustrating the initial state of the first subtank 411 and the second subtank 431 in the full-range correction described in FIG. 6. FIG. 7B is a diagram illustrating a state in which the liquid levels in the first subtank 411 and the second subtank 431 are aligned in the full-range correction described in FIG. 6. FIG. 7C is a diagram illustrating a state in which the first subtank 411 is sealed in the full-range correction described in FIG. 6. FIG. 7D is a diagram illustrating a state in which ink I is being sent from the first subtank 411 to the second subtank 431 in the full-range correction described in FIG. 6.

[0098] 6, the first sub-tank 411 is represented as "1ST" and the second sub-tank as "2ST." Also, in FIGS. 7A to 7D, the first sub-tank section 410, the liquid supply section 420, and the second sub-tank section 430 are partially omitted from illustration, and the head module 50 is also omitted from illustration. Also, here, the reference heights in the reference height detection sections D1 and D2 are the lower limits of the first sub-tank 411 and the second sub-tank 431, respectively.

[0099] In the initial state of the full-area correction described below, the liquid level height of the ink I in both the first subtank 411 and the second subtank 431 is between the upper and lower limits, as shown in Fig. 7A. At this time, the valve 417 (see Fig. 1) of the first subtank 411 is in an open state under the control of the measurement control unit 448 (acquisition unit), and the upper space of the first subtank 411 is in a state where it is open to the atmosphere. Also, under the control of the measurement control unit 448 (acquisition unit), the air pump 432 (see Fig. 1) of the second subtank 431 controls the pressure of the upper space of the second subtank 431 to a desired pressure (for example, -3 kPa).

[0100] (Step S21) As shown in FIG. 7B, the measurement control unit 448 (acquisition unit) adjusts the liquid surface height of the ink I in the first sub-tank 411 and the second sub-tank 431 to their respective lower limits.

[0101] For example, the measurement control unit 448 (acquisition unit) drives the liquid feed pump 423 to feed ink I from the first subtank 411 to the second subtank 431, and uses the reference height detection unit D1 (see FIG. 1) to adjust the liquid level of the ink I in the first subtank 411 to the lower limit. Thereafter, the measurement control unit 448 (acquisition unit) uses the head module 50 to eject ink I from the second subtank 431, and uses the reference height detection unit D2 (see FIG. 1) to adjust the liquid level of the ink I in the second subtank 431 to the lower limit.

[0102] If the liquid level height of the ink I in the first subtank 411 deviates from the lower limit, the relationship L=f(P) explained later in Figure 8A changes, and the full-area correction becomes inaccurate. Therefore, it is important to adjust the liquid level height of the ink I in the first subtank 411 to the lower limit, and another reference height detection device may be used in addition to or instead of the reference height detection unit D1.

[0103] Furthermore, if the liquid level of the ink I deviates from the lower limit in the second subtank 431, the liquid level will deviate from the true value. Therefore, it is also important to adjust the liquid level of the ink I in the second subtank 431 to the lower limit, and another reference height detection device may be used in addition to or instead of the reference height detection unit D2.

[0104] (Step S22) As shown in FIG. 7C, the measurement control unit 448 (acquisition unit) closes the valve 417 (see FIG. 1) to seal the first sub-tank 411.

[0105] (Step S23) After sealing the first sub-tank 411, the measurement control unit 448 (acquisition unit) drives the liquid feed pump 423 to feed the ink I from the first sub-tank 411 to the second sub-tank 431.

[0106] (Step S24) The measurement control unit 448 (acquisition unit) uses the pressure sensor 418 (see FIG. 1) to acquire the pressure value inside the sealed first sub-tank 411, and also acquires the sensor output value of the Hall sensor 446 (see FIG. 1).

[0107] 8A, the pressure value inside the first subtank 411 changes in accordance with changes in the liquid level of the ink I inside the first subtank 411, and the sensor output value of the Hall sensor 446 also changes in accordance with changes in the liquid level of the ink I inside the second subtank 431. Using the pressure value and sensor output value that change in this way, a relational expression (described later) is found to perform full-range correction.

[0108] (Step S25) The measurement control unit 448 (acquisition unit) checks whether the liquid level of the ink I in the second sub-tank 431 is at the upper limit. If the liquid level of the ink I in the second sub-tank 431 is at the upper limit (YES), the process proceeds to step S26, and if the liquid level of the ink I in the second sub-tank 431 is not at the upper limit, that is, if it is below the upper limit (NO), steps S24 and S25 are repeated.

[0109] The upper limit of the second sub-tank 431 can be determined, for example, by placing a reed switch similar to the reed switch 445 used in the reference height detection unit D2 at the upper limit position, and using this reed switch to check whether the liquid level of the ink I in the second sub-tank 431 is at the upper limit.

[0110] 7D, the measurement control unit 448 (acquisition unit) changes the liquid level of the ink I in the second subtank 431 from the lower limit to the upper limit. At this time, the measurement control unit 448 (acquisition unit) acquires the pressure value in the first subtank 411 and the sensor output value of the Hall sensor 446 of the second subtank 431 that accompany the change in the liquid level from the lower limit to the upper limit.

[0111] When ink I is sent from the first subtank 411 to the second subtank 431, the liquid level in the first subtank 411 drops. Because the first subtank 411 is sealed, the volume of air increases by the volume of the sent liquid, and the pressure value in the first subtank 411 drops. Meanwhile, as the liquid is sent, the liquid level in the second subtank 431 rises, and the sensor output value of the Hall sensor 446 of the second subtank 431 increases. The measurement control unit 448 (acquisition unit) acquires these changes in pressure value and changes in sensor output value in association with each other.

[0112] (Step S26) The measurement control unit 448 (acquisition unit) turns off the liquid feed pump 423 (also closes the liquid feed valve 424) and stops the feeding of the ink I from the first sub-tank 411 to the second sub-tank 431.

[0113] (Step S27) The measurement control unit 448 (acquisition unit) obtains the relationship (relational formula) between the sensor output value and the liquid level in the second sub-tank 431 based on the pressure value in the first sub-tank 411 and the sensor output value of the hall sensor 446 of the second sub-tank 431.

[0114] Here, the relational expression obtained by the full-range correction will be described with reference to Figures 8A and 8B. Figure 8A is a diagram illustrating the relationship between the liquid level height and sensor output value of the second sub-tank 431 relative to the pressure value of the first sub-tank 411 in the full-range correction described in Figure 6. Figure 8B is a graph showing the relationship (relational expression) between the sensor output value and the liquid level height obtained from the relationship shown in Figure 8A. Note that in Figures 8A and 8B as well, the first sub-tank 411 will be referred to as "1ST" and the second sub-tank as "2ST."

[0115] First, using a method substantially similar to that described with reference to FIGS. 6 and 7A to 7D, a relational expression between the pressure value P of the first subtank 411 and the liquid level height L of the second subtank 431 is determined in advance using experimental or calculated values. That is, while the method described with reference to FIGS. 6 and 7A to 7D acquires the sensor output value of the Hall sensor 446 of the second subtank 431, here the liquid level L of the second subtank 431 is determined by experiment or calculation instead. This determines the relational expression L=f(P) shown in FIG. 8A, i.e., the relational expression between the pressure value P of the first subtank 411 and the liquid level height L of the second subtank 431. The measurement control unit 448 stores the relational expression L=f(P) in a memory unit.

[0116] 6 and 7A to 7D, i.e., full-range correction, when the relational expression L=f(P) is stored in the memory section. In FIG. 8A, the "initial state" is the state shown in FIG. 7A. Furthermore, "liquid level matching" is the state shown in step S21 in FIG. 6 and FIG. 7B. Furthermore, "sealed" is the state shown in step S22 in FIG. 6 and FIG. 7C. Furthermore, "liquid transfer" is the state shown in steps S23 to S26 in FIG. 6 and FIG. 7D. During "liquid transfer," the relational expression P=g(V) shown in FIG. 8A, i.e., the relational expression between the pressure value P of the first sub-tank 411 and the sensor output value V of the Hall sensor 446 of the second sub-tank 431, is obtained.

[0117] Then, the measurement control unit 448 (acquisition unit) obtains the relational expression L=f(g(V)) using the relational expression L=f(P) stored in advance in the storage unit and the relational expression P=g(V) obtained by the full-range correction. In other words, the measurement control unit 448 (acquisition unit) obtains the relational expression L=f(g(V)) of the sensor output value V of the Hall sensor 446 of the second subtank 431 relative to the liquid level L of the second subtank 431 (see FIG. 8B). Using this relational expression L=f(g(V)), it is possible to calculate a more accurate liquid level in the range from the lower limit to the upper limit of the second subtank 431.

[0118] As described above, the measurement control unit 448 (acquisition unit) obtains the relational expression L=f(g(V)). Then, the measurement control unit 448 (correction unit) performs full-range correction using the relational expression L=f(g(V)) in the range from the lower limit to the upper limit of the second subtank 431, even if there is a change over time, and therefore can calculate a more accurate liquid level height.

[0119] It is also possible to perform correction 2 without performing correction 1. However, correction 2 involves consumption of ink I. Therefore, taking into consideration the consumption of ink I, it is desirable to perform correction 1, and then perform correction 2 when the difference Δb becomes equal to or greater than a predetermined value.

[0120] [Abnormality determination method] The above-described correction 1 and correction 2 make it possible to accurately measure the liquid level even if there is a change over time. Taking advantage of this, the ink liquid level measuring device 440 may be provided with a determination unit that determines whether there is an abnormality in the liquid delivery unit 420. The determination unit is also provided as a function of the measurement control unit 448, and is provided as a program executed by the measurement control unit 448, for example.

[0121] For example, the measurement control unit 448 (determination unit) ejects ink I to adjust (lower) the liquid level to a target height while measuring the liquid level of ink I in the second subtank 431 with the ink level measurement device 440. This target height may be a height different from the reference height (for example, the lower limit) described above, and can be set to an appropriate height as long as the liquid level in the second subtank 431 after the ink I has been delivered does not exceed the upper limit of the second subtank 431.

[0122] If the target height is the above-mentioned reference height (for example, the lower limit), the above-mentioned correction 1 may be executed at the time of determination by the determination unit.

[0123] After adjusting the liquid level of the ink I in the second subtank 431 to the target level, the measurement control unit 448 (determination unit) drives the liquid feed pump 423 for a predetermined time (for example, 10 seconds) to feed the ink I from the first subtank 411 to the second subtank 431. The predetermined time for driving the liquid feed pump 423 can be set to any appropriate time as long as the liquid level in the second subtank 431 after the ink I has been fed does not exceed the upper limit of the second subtank 431.

[0124] By the above procedure, the measurement control unit 448 (determination unit) can obtain the liquid level height and the rate of change of the liquid level with respect to the target height for the driving time of the liquid feed pump 423. Then, the measurement control unit 448 (determination unit) can determine the state of the liquid feed unit 420 (tank supply path 421) based on the liquid level height and the rate of change of the liquid level with respect to the reference height.

[0125] FIG. 9 is a graph showing the relationship between the driving time of the liquid feed pump 423 and the liquid level of the ink I in the second sub-tank 431, from when the ink supply unit 40 is brand new to when it is determined to be faulty.

[0126] As shown in Figure 9, the liquid level of ink I in the second sub-tank 431 increases linearly with the operating time of the liquid supply pump 423, but the rate of change of the liquid level decreases as the ink supply unit 40 goes from a new state to a state where it is determined to be faulty.

[0127] For example, in the ink supply unit 40, the liquid delivery unit 420 has a filter 425 that filters the ink I. As the filter 425 becomes increasingly clogged over time, the amount of ink I delivered from the first sub-tank 411 to the second sub-tank 431 also decreases over time.

[0128] Therefore, as described above, the measurement control unit 448 (determination unit) drives the liquid feed pump 423 for a predetermined time to feed the ink I from the first sub-tank 411 to the second sub-tank 431. Then, the measurement control unit 448 (determination unit) determines the state (whether or not there is a malfunction) of the liquid feed unit 420 based on the liquid level height and the rate of change of the liquid level height relative to a reference height (for example, the position before the liquid feed).

[0129] 10 is a graph illustrating the results of a determination based on the change over time in the amount of ink I delivered after being supplied for a predetermined period of time. In this embodiment, the ink level measurement device 440 measures the liquid level as a continuous value, unlike the devices disclosed in Patent Documents 1 and 2 that detect the liquid level discretely. Therefore, by monitoring the liquid level and the rate of change of the liquid level relative to a reference level over time (e.g., daily), the ink level measurement device 440 can determine the degree of deterioration of the liquid delivery unit 420 between a brand new state and a faulty state, as shown in FIG.

[0130] Furthermore, by monitoring the ink level relative to a reference level and the rate of change of the ink level over time, the ink level measuring device 440 can also predict the degree of deterioration and the timing of a malfunction, as shown in Figure 10. In this way, since the degree of deterioration can be predicted, for example, by predicting the timing of 80% deterioration and replacing the deteriorated part at the predicted 80% deterioration timing, it is possible to prevent the ink delivery unit 420 from malfunctioning and the inkjet printer 100 from shutting down. In other words, by replacing the deteriorated part before a malfunction occurs, it is possible to prevent the ink delivery unit 420 from malfunctioning and the inkjet printer 100 from shutting down.

[0131] Furthermore, when the liquid supply pump 423 is driven for a predetermined time to supply ink I from the first sub-tank 411 to the second sub-tank 431, the pump duty of the liquid supply pump 423 can be changed to identify the location of a failure in the liquid supply unit 420.

[0132] In the liquid delivery unit 420, the main failure points are the liquid delivery pump 423 and the filter 425. According to the inventor's knowledge, when it is desired to determine whether the liquid delivery pump 423 has deteriorated, it is sufficient to set the pump duty to a relatively low value, and when it is desired to determine whether the filter 425 has deteriorated, it is sufficient to set the pump duty to a relatively high value.

[0133] For example, it is assumed that the settable range of the pump duty of the liquid feed pump 423 is 20% to 100%. In this case, when it is desired to determine whether the liquid feed pump 423 has deteriorated, the pump duty is set to, for example, 20%, and when it is desired to determine whether the filter 425 has deteriorated, the pump duty is set to, for example, 100%.

[0134] This is because the resistance (pressure loss) of the filter 425 increases as the square of the flow rate of the ink I, so if the pump duty is set to a relatively high value, the resistance due to clogging of the filter 425 increases, making it possible to determine whether the filter 425 has deteriorated.

[0135] Furthermore, if the pump duty is set to a relatively low value, the effect of the resistance of the filter 425 is reduced and the effect of deterioration of the liquid feed pump 423 is increased, making it possible to determine whether the liquid feed pump 423 has deteriorated. Furthermore, if the pump duty is set to a relatively low value, the flow rate of the ink I in the liquid feed pump 423 also slows. Therefore, for example, if a gap is formed in the check valve portion in the liquid feed pump 423 due to solidified matter or the like, the flow path resistance in that portion decreases, making it easier for backflow to occur and reducing the amount of liquid fed, making it possible to determine whether the liquid feed pump 423 has deteriorated.

[0136] As described above, the measurement control unit 448 (determination unit) determines the state of the liquid delivery unit 420 based on the liquid level height relative to the reference height and the rate of change of the liquid level height, so it can determine whether the liquid delivery unit 420 is malfunctioning or not, and can also predict the degree of deterioration and the time of malfunction.

[0137] In addition, the following supplementary notes are provided in relation to the above description. (Appendix 1) An ink level measuring device for measuring the ink level in a container, a float having a magnet and moving in accordance with the change in the liquid level; a Hall element that detects, as a continuous value, a change in magnetic flux density caused by the magnet that moves together with the float; an acquisition unit that acquires a pressure value of air in the supply source container and an output value of the Hall element while supplying the ink from a sealed supply source container to the container and changing the liquid level height from a lower limit to an upper limit of the container, and acquires a relational expression for correcting the liquid level height over the entire range from the lower limit to the upper limit based on the pressure value and the output value; a correction unit that corrects the liquid level using the relational expression; An ink level measuring device comprising:

[0138] The above-described embodiments are merely examples of specific embodiments for carrying out the present invention, and the technical scope of the present invention should not be construed as being limited by these embodiments. In other words, the present invention can be carried out in various forms without departing from the gist or main features thereof.

[0139] For example, in the above embodiment, the measurement control unit 448 functions as the above-mentioned adjustment unit, correction unit, acquisition unit, and judgment unit, but the control unit 90 may be configured to function as the above-mentioned adjustment unit, correction unit, acquisition unit, and judgment unit. [Explanation of symbols]

[0140] 10 Conveying section 20 Supply section 30 Discharge section 40 Ink supply unit 50 head modules 70 Operation display section 80 Input / Output Interface 90 Control Unit 100 Inkjet Printer 200 External device 410 1st subtank section 411 1st Subtank 412 Float 413 Information Department 414 Magnet 416 Reed Switch 417 Valve 418 Pressure Sensor 420 Liquid delivery unit 421 Tank supply line 422 Degassing Module 423 Liquid transfer pump 424 Liquid transfer valve 425 Filter 430 Second sub-tank section 431 Second Subtank 432 Pneumatic Pump 433 Head supply path 440 Ink level measuring device 441 Float 442 Information Department 443 Magnet 445 Reed Switch 446 Hall Sensor 447 Magnetic material 448 Measurement control section

Claims

1. An ink level measuring device for measuring the ink level in a container, a float having a magnet and moving in accordance with the change in the liquid level; a Hall element that detects, as a continuous value, a change in magnetic flux density caused by the magnet that moves together with the float; an adjusting unit that adjusts the liquid level to a reference height; a correction unit that acquires an output value of the Hall element when the liquid level is at the reference level, and corrects the liquid level based on the output value; An ink level measuring device comprising:

2. The housing of the Hall element includes a magnetic material. The ink level measuring device according to claim 1 .

3. the correction unit corrects the liquid level based on an initial value and a current value of the output of the Hall element when the liquid level is at the reference height. The ink level measuring device according to claim 1 .

4. the correction unit corrects the liquid level by adding a difference between the initial value and the current value as a correction term in a calculation formula for calculating the liquid level. The ink level measuring device according to claim 3 .

5. further comprising an acquisition unit that acquires a relational expression for correcting the liquid level in the entire range from the lower limit to the upper limit of the liquid level when the difference becomes 0.5% or more with respect to the initial value, The correction unit corrects the liquid level height using the relational expression.

5. The ink level measuring device according to claim 4.

6. the acquisition unit acquires a pressure value of the air in the supply source container and an output value of the Hall element while supplying the ink from a sealed supply source container to the container and changing the liquid level in the container from the lower limit to the upper limit, and acquires the relational expression based on the pressure value and the output value. The ink level measuring device according to claim 5 .

7. a determination unit that determines a state of the ink supply path to the container based on the liquid level or a rate of change of the liquid level relative to the reference level, The ink level measuring device according to claim 1 .

8. When the determination unit determines The adjusting unit adjusts the liquid level to the reference height, the correction unit acquires an output value of the Hall element when the liquid level is at the reference height. The ink level measuring device according to claim 7 .

9. the determining unit determines the state of the ink supply path based on a rate of change in the liquid level when the ink is supplied to the container for a predetermined time. The ink level measuring device according to claim 7 .

10. a container for storing ink; an image forming unit that forms an image using the ink supplied from the container; The ink level measuring device according to claim 1 ; Equipped with Image forming device.

11. During image formation by the image forming unit, The adjusting unit adjusts the liquid level to the reference height, the correction unit acquires an output value of the Hall element when the liquid level is at the reference height. The image forming apparatus according to claim 10.

12. the adjusting unit supplies the ink to the container when the liquid level of the ink in the container falls below the reference level due to image formation by the image forming unit, and stops supplying the ink when the liquid level reaches the reference level. The image forming apparatus according to claim 11.

Images