Ink level height measurement device and image formation device

Abstract

To measure an ink level height continuously with high accuracy.SOLUTION: An ink level height measurement device includes: a detection part for detecting a change in physical quantity with a change in ink level height inside a container as a continuous value; and a measurement part for obtaining a level height on the basis of the detected physical quantity.SELECTED DRAWING: Figure 1

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 type image forming apparatus, a tank that stores ink to be supplied to an inkjet head is provided with an ink level measuring device (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-141547 A [Patent Document 2] Patent Publication No. 2021-783 Summary of the Invention [Problem to be solved by the invention]

[0004] In the ink level measuring devices disclosed in Patent Documents 1 and 2, the upper and lower limits of the liquid level are detected, and the measured liquid level is discrete. Therefore, the liquid level between the upper and lower limits is unknown, and there is a problem that it is difficult to judge whether the ink supply device has a fault, or even if it can be judged, the accuracy of the fault judgment is insufficient.

[0005] An object of the present invention is to provide an ink level measuring device and an image forming apparatus that are capable of continuously measuring the ink level with high accuracy. [Means for solving the problem]

[0006] The ink level measuring device according to the present invention comprises: a detection unit that detects a change in a physical quantity accompanying a change in the liquid level of the ink in the container as a continuous value; A measuring unit that determines the liquid level based on the detected physical quantity; Equipped with.

[0007] 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 level measuring device; Equipped with. Effect of the Invention

[0008] According to the present invention, the ink level can be measured continuously and with high accuracy. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus and an ink level measuring device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram showing a main part of a control system of the image forming apparatus shown in FIG. [Diagram 3] FIG. 3 is a schematic diagram illustrating the ink level measuring device shown in FIG. [Figure 4] FIG. 4 is a schematic diagram illustrating a modification of the ink level measuring device shown in FIG. [Figure 5A] FIG. 5A is a graph showing the relationship between magnetic flux density and liquid level at the sensor position for the sensor of the ink level measuring device shown in FIG. [Figure 5B] 5B is a graph showing the relationship between the sensor output value and the magnetic flux density for the sensor of the ink level measuring device shown in FIG. [Figure 5C] FIG. 5C is a graph showing the relationship between the sensor output value and the ink level for the sensor of the ink level measuring device shown in FIG. [Figure 6A] FIG. 6A shows the results of an analysis, using a general-purpose finite element electromagnetic field analysis tool, of the magnetic field when a magnetic body is placed close to the underside of the sensor. [Figure 6B] FIG. 6B shows the results of an analysis, using a general-purpose finite element electromagnetic field analysis tool, of the magnetic field when a magnetic body is placed adjacent to the upper side of the sensor. [Figure 7] FIG. 7 is a graph comparing the magnetic flux density at the sensor position when a magnetic body is placed close to the lower side of the sensor and when a magnetic body is placed close to the upper side of the sensor. [Figure 8A] FIG. 8A shows the results of an analysis of the magnetic field when a magnetic body is placed away from the sensor, using a general-purpose finite element method electromagnetic field analysis tool. [Figure 8B] FIG. 8B shows the results of an analysis of the magnetic field when a magnetic body is placed close to the sensor, using a general-purpose finite element method electromagnetic field analysis tool. [Figure 9] FIG. 9 is a graph showing the relationship between the magnetic flux density at the sensor position and the distance between the sensor and the magnetic body. [Figure 10] FIG. 10 is a graph showing the relationship between the magnetic flux density at the sensor position and the magnetic body width. [Figure 11] FIG. 11 is a graph showing the relationship between the magnetic flux density at the sensor position and the thickness of the magnetic material. [Figure 12] FIG. 12 is a graph showing the relationship between the magnetic flux density at the sensor position and the depth of the magnetic body. [Figure 13] FIG. 13 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 broken. [Figure 14] FIG. 14 is a graph illustrating the results of determination based on the change over time in the amount of ink delivered in a predetermined period of time. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0011] [Image forming device] Fig. 1 is a schematic diagram illustrating an example of an inkjet printer 100 (an image forming apparatus in 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.

[0012] As shown in FIG. 2, the inkjet printer 100 includes a transport section 10, a supply section 20, a discharge section 30, an ink supply 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, etc.

[0013] 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 supply 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.

[0014] 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 be a medium such as roll-shaped paper, cloth, or resin.

[0015] 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.

[0016] The discharge unit 30 stores the recording medium M discharged from the transport unit 10. The discharge unit 30 has, for example, a belt or rollers that transport the recording medium M from the transport unit 10, and has a storage unit that stores the recording medium M.

[0017] 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 measurement device 440, and the like.

[0018] 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 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).

[0019] 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 pump 423, a valve 424, and the like.

[0020] 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 filters the ink I by the filter 425.

[0021] The pump 423 is a pump that sends the ink I from the first sub-tank 411 to the second sub-tank 431. The valve 424 opens and closes the tank supply path 421. For example, when sending the ink I from the first sub-tank 411 to the second sub-tank 431, the valve 424 opens, and when sending the ink I from the second sub-tank 431 to the head module 50, the valve 424 closes.

[0022] The second sub-tank unit 430 stores the ink I to be sent to the head module 50. The second sub-tank unit 430 has 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.

[0023] 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 .

[0024] The air pressure pump 432 is connected to the upper part of the second subtank 431, and supplies air to the upper space of the second subtank 431 to control the air present in the upper space to a desired pressure. The head supply path 433 connects the lower part of the second subtank 431 to the head module 50. When the air in the upper space of the second subtank 431 is controlled to a desired pressure, the ink I in the second subtank 431 is pushed out towards the head supply path 433 by the air pressure, and is sent to the head module 50.

[0025] The above-mentioned second sub-tank portion 430 is provided with an ink level measuring device 440 that measures the level of the ink I in the second sub-tank 431. The 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.

[0026] The head module 50 has devices and members necessary for image formation, such as an inkjet head. The head module 50 ejects ink I supplied from the ink supply unit 40 (second sub-tank unit 430) from the inkjet head to form an image on the recording medium M.

[0027] 1, for the sake of 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 using four colors, yellow (Y), magenta (M), cyan (C), and black (K), ink supply units 40 and head modules 50 for four colors are arranged.

[0028] The operation display unit 70 is, for example, a flat panel display such as a liquid crystal display or an organic EL (Electro Luminescence) display with a touch panel. The operation display unit 70 displays an operation menu for the user, information related to image data, various states of the inkjet printer 100, and the like. The operation display unit 70 also includes a plurality of keys and accepts various input operations from the user.

[0029] 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.

[0030] 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 an input / output interface 80 .

[0031] 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, etc.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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 HDD (Hard Disk Drive) is used, and a DRAM (Dynamic Random Access Memory) or the like may also be used in combination.

[0036] 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 display unit 70, input / output interface 80, etc. The control unit 90 comprehensively 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 display unit 70, input / output interface 80, etc. are controlled by the control unit 90 to execute predetermined processes.

[0037] With the above-described 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.

[0038] [Ink level measuring device] Fig. 3 is a schematic diagram illustrating the ink level measuring device 440 shown in Fig. 1. Fig. 4 is a schematic diagram illustrating a modified example of the ink level measuring device 440 shown in Fig. 3.

[0039] 1, an ink level measuring device 440 is provided in the second sub-tank unit 430 of the ink supply unit 40. As shown in FIG. 3, the ink level measuring device 440 has a float 441, a guide unit 442, magnets 443 and 444, a sensor 445 (a detection unit in the present invention), a magnetic body 446, a measuring unit 447, and the like.

[0040] Float 441 is a float that floats on the surface of ink I. In plan view, a through hole into which guide portion 442 is inserted is formed in the center of float 441.

[0041] The guide portion 442 is a rod-shaped member that extends downward and has an end supported on the top plate side of the second sub-tank 431. The guide portion 442 is inserted into a through-hole of the float 441. The guide portion 442 prevents the float 441 from tilting, and guides the float 441 so that it can move in the vertical direction, which is the liquid level height direction, that is, so that it can move up and down. Therefore, the float 441 moves up and down along the guide portion 442 in accordance with the up and down movement of the liquid level of the ink I.

[0042] Note that guide portion 442 may be a rod-shaped member whose end is supported on the bottom plate side of second sub-tank 431 and extends upward, so long as it can regulate float 441 so as to prevent it from tilting and can guide float 441 so as to be vertically movable. Also, as shown in Fig. 4, guide portion 442 may be omitted. In the example shown in Fig. 4, float 441 does not have a through hole and is formed so that its outer peripheral side surface is close to the inner wall of second sub-tank 431. The inner wall of second sub-tank 431 regulates float 441 so as to prevent it from tilting and also functions as a guide portion that guides float 441 so as to be vertically movable.

[0043] Magnets 443 and 444, which are permanent magnets, are disposed inside float 441. Magnets 443 and 444 are disposed in positions inside float 441 that maintain balance so that float 441 floating on the surface of ink I does not tilt, in other words, in positions where the positions of magnets 443 and 444 relative to sensor 445 do not change in the horizontal direction along the liquid surface.

[0044] 4, if there is no guide portion 442, there is no need to form a through hole in the center of float 441. Therefore, a magnet 443 is placed in the center of float 441 so that float 441 floating on the surface of ink I does not tilt.

[0045] Although there are the above-mentioned differences between the ink level measuring device 440 shown in FIG. 3 and the ink level measuring device 440 shown in FIG. 4, they have the same basic configuration.

[0046] The sensor 445 is a magnetic sensor. For example, a Hall element can be used as the magnetic sensor, and the sensor 445 may include an operational amplifier circuit or the like.

[0047] The sensor 445 is disposed at a position where it can measure a change in magnetic flux density caused by the magnets 443, 444 moving up and down together with the float 441, preferably at a position where the magnetic flux density is large. For example, the sensor 445 is fixed to the top plate side of the second subtank 431 together with the magnetic body 446, and disposed at a position facing the magnet 443 in the vertical direction. The sensor 445 and the magnetic body 446 may also be fixed to the bottom plate side of the second subtank 431, and disposed at a position facing the magnet 443 in the vertical direction.

[0048] Here, Fig. 5A is a graph showing the relationship between the magnetic flux density at the sensor position and the liquid level for sensor 445 of ink level measuring device 440. Fig. 5B is a graph showing the relationship between the sensor output value and the magnetic flux density for sensor 445. Fig. 5C is a graph showing the relationship between the sensor output value and the liquid level for sensor 445.

[0049] As shown in Fig. 5A, the magnetic flux density by magnets 443, 444 at the position of sensor 445 increases exponentially as the liquid level increases, that is, as magnets 443, 444 approach sensor 445. In addition, the sensor output value output from sensor 445 used here decreases inversely proportional to the magnetic flux density of the magnetic field, as shown in Fig. 5B. Therefore, the sensor output value of sensor 445 decreases quadratically as the liquid level increases, as shown in Fig. 5C. In this way, sensor 445 detects the change in magnetic flux density, which is a change in physical quantity accompanying the change in liquid level, as a continuous value, and outputs the sensor output value.

[0050] The magnetic body 446 is a member made of iron or the like having high magnetic permeability. As an example, the magnetic body 446 is a rectangular plate-shaped member. Hereinafter, the magnetic body 446 is assumed to be a rectangular plate-shaped member.

[0051] Here, the arrangement of the magnetic body 446, specifically the upper and lower positions of the magnetic body 446 with respect to the sensor 445, will be described with reference to FIGS. 3 and 4 as well as FIGS. 6A to 7. FIG. 6A shows the result of an analysis of a magnetic field when a magnetic body is arranged close to the lower side of the sensor, using a general-purpose finite element method electromagnetic field analysis tool. FIG. 6B shows the result of an analysis of a magnetic field when a magnetic body is arranged close to the upper side of the sensor, using a general-purpose finite element method electromagnetic field analysis tool. FIG. 7 is a graph comparing the magnetic flux density at the sensor position when a magnetic body is arranged close to the lower side of the sensor and when a magnetic body is arranged close to the upper side of the sensor.

[0052] In the following description, the direction of the central axis C of the second sub-tank 431 is defined as the vertical direction, and the direction perpendicular to the central axis C is defined as the radial direction (the perpendicular direction in the present invention).

[0053] Normally, a magnetic field is distorted toward a material with high magnetic permeability, such as a magnetic body, and magnetic flux is concentrated. As shown in Fig. 6A, when a magnetic body is placed close to the lower side of the sensor, the magnetic field flows radially due to the magnetic body below the sensor, and the magnetic flux density at the sensor position is small. On the other hand, as shown in Fig. 6B, when a magnetic body is placed close to the upper side of the sensor, the magnetic field is distorted toward the magnetic body, and magnetic flux is concentrated, so the magnetic flux density at the sensor position is large.

[0054] Therefore, as shown in the graph in Figure 7, the magnetic flux density at the sensor position is greater when a magnetic material is placed close to the above the sensor than when it is placed close to the below the sensor, so it is desirable to place the magnetic material above the sensor.

[0055] The arrangement of the magnetic body 446, specifically the distance between the sensor 445 and the magnetic body 446, will be described with reference to Figs. 8A to 9. Fig. 8A shows the result of an analysis, using a general-purpose finite element method electromagnetic field analysis tool, of a magnetic field when the magnetic body is arranged away from the sensor. Fig. 8B shows the result of an analysis, using a general-purpose finite element method electromagnetic field analysis tool, of a magnetic field when the magnetic body is arranged close to the sensor. Fig. 9 is a graph showing the relationship between the magnetic flux density at the sensor position and the distance between the sensor and the magnetic body.

[0056] In the following description, the length (width) of magnet 443 in the radial direction is designated as a, and the maximum distance between magnet 443 and sensor 445 is designated as b, as shown in FIGS.

[0057] As described above, the magnetic field is usually distorted toward the magnetic body, and the magnetic flux is concentrated. Therefore, when the magnetic body is placed close to the sensor (FIG. 8B), the magnetic field penetrating the sensor is more vertical than when the magnetic body is placed farther away from the sensor (FIG. 8A). When the magnetic field penetrating the sensor is made vertical by the magnetic body, it becomes the same direction as the magnetic field with high detection sensitivity of the sensor used in this embodiment, and the detected magnetic flux density becomes large.

[0058] When we checked the relationship between the magnetic flux density at the sensor position and the distance between the sensor and the magnetic body, we found that the magnetic flux density at the sensor position decreases as the distance between the sensor and the magnetic body increases, as shown in the graph in Figure 9. In addition, in the graph in Figure 7, the dotted line indicates the magnetic flux density at the sensor position when there is no magnetic body.

[0059] In the graph in Fig. 7, the distance between the sensor and the magnetic body is expressed using the dimensionless number a / b. In the graph shown in Fig. 7, when the distance between the sensor and the magnetic body is 3×a / b or more, it is estimated that the magnetic flux density at the sensor position is close to the magnetic flux density when there is no magnetic body.

[0060] On the other hand, when the distance between the sensor and the magnetic body is 2×a / b or less, the magnetic flux density at the sensor position is greater than the magnetic flux density when there is no magnetic body, and when the distance is a / b or less, it is even greater. Therefore, it is desirable to place the magnetic body within 2×a / b around the sensor, and it is even more desirable to place it within a / b.

[0061] The size of the magnetic body 446 will be described with reference to Fig. 10 and Fig. 11. Fig. 10 is a graph showing the relationship between the magnetic flux density at the sensor position and the magnetic body width. Fig. 11 is a graph showing the relationship between the magnetic flux density at the sensor position and the magnetic body thickness. Fig. 12 is a graph showing the relationship between the magnetic flux density at the sensor position and the magnetic body depth.

[0062] When the relationship between the magnetic flux density at the sensor position and the magnetic body width (the width of the magnetic body 446 in the radial direction) was confirmed, the magnetic flux density at the sensor position increased as the magnetic body width increased, as shown in the graph of Fig. 10. In the graph of Fig. 10, the dotted line indicates the magnetic flux density at the sensor position when there is no magnetic body.

[0063] In the graph of Fig. 10, the magnetic body width is expressed using the dimensionless number b / a. In the graph shown in Fig. 10, when the magnetic body width is b / a or less, it is estimated that the magnetic flux density at the sensor position is close to the magnetic flux density when there is no magnetic body.

[0064] On the other hand, when the magnetic body width is 2×b / a or more, the magnetic flux density at the sensor position becomes larger than the magnetic flux density when there is no magnetic body, and when it is 3×b / a or more, it becomes even larger. Therefore, it is desirable for the magnetic body width to be 2×b / a or more, and more desirably 3×b / a or more.

[0065] In addition, when the relationship between the magnetic flux density at the sensor position and the thickness of the magnetic body (the thickness of the magnetic body 446 in the vertical direction) was confirmed, as shown in the graph of Fig. 11, the magnetic flux density at the sensor position increases as the magnetic body thickness increases. Therefore, it is desirable for the magnetic body thickness to be large. In the graph of Fig. 11, the dotted line indicates the magnetic flux density at the sensor position when there is no magnetic body.

[0066] In addition, when the relationship between the magnetic flux density at the sensor position and the magnetic body depth (the depth of the magnetic body 446 in the direction perpendicular to the radial direction) was confirmed, as shown in the graph of Fig. 12, the magnetic flux density at the sensor position increases as the magnetic body depth increases. Therefore, it is desirable that the magnetic body depth is large. In the graph of Fig. 12, the dotted line indicates the magnetic flux density at the sensor position when there is no magnetic body.

[0067] For these reasons, it is desirable to place magnetic body 446 close to the upper side of sensor 445, and it is desirable for the size (width, thickness, and depth) to be large.

[0068] Since the magnetic body 446 is disposed close to the upper side of the sensor 445, the sensor 445 detects the level of the ink I, 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 outputs an output value corresponding to the level of the ink I (see FIGS. 5A to 5C). As a result, the ink level measuring device 440 can continuously measure the level of the ink I with high accuracy.

[0069] The measuring unit 447 obtains the liquid level based on the output value from the sensor 445 (see FIG. 5C). The measuring unit 447 also determines the state of the liquid delivery unit 420 (tank supply path 421) based on the liquid level relative to a reference level and the rate of change of the liquid level (the determining unit in the present invention).

[0070] For example, the control unit 90 drives the air pressure pump 432 to adjust (lower) the liquid level to a reference height while measuring the liquid level of the ink I in the second subtank 431 with the ink level measuring device 440. The reference height can be set to an appropriate height as long as the liquid level in the second subtank 431 after the ink I is delivered, which will be described later, does not exceed the upper limit height of the second subtank 431.

[0071] After adjusting the liquid level of the ink I in the second subtank 431 to the reference height, the control unit 90 drives the pump 423 for a predetermined time (e.g., 10 seconds) to send the ink I from the first subtank 411 to the second subtank 431. The predetermined time for driving the pump 423 can be set to an appropriate time as long as the liquid level in the second subtank 431 after sending of the ink I does not exceed the upper limit height of the second subtank 431. Through the above procedure, the measurement unit 447 can obtain the liquid level height and the rate of change of the liquid level height relative to the reference height for the driving time of the pump 423.

[0072] Here, FIG. 13 is a graph showing the relationship between the drive time of the pump 423 and the liquid level of the ink I in the second sub-tank 431 from a state in which the ink supply unit 40 is brand new to a state in which it is determined to be broken.

[0073] As shown in FIG. 13, the liquid level of the ink I in the second sub-tank 431 increases linearly with the operating time of the 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.

[0074] For example, in the ink supply unit 40, the liquid sending unit 420 has a filter 425 that filters the ink I. Since the filter 425 becomes clogged over time, the amount of ink I sent from the first sub-tank 411 to the second sub-tank 431 also decreases over time.

[0075] Therefore, by driving the pump 423 for a predetermined period of time, ink I is sent from the first sub-tank 411 to the second sub-tank 431, and the ink sending unit 420 can determine its condition (whether or not it is broken) based on the liquid level height and the rate of change of the liquid level height relative to a reference height (e.g., the position before the liquid is sent).

[0076] 14 is a graph illustrating the result of determination based on the change over time in the amount of ink I sent over a predetermined period of time. In this embodiment, the ink level measuring device 440 measures the level as a continuous quantity, unlike the devices disclosed in Patent Documents 1 and 2 that detect the level discretely. Therefore, the ink level measuring device 440 monitors the level and the rate of change of the level relative to the reference level over time (e.g., every day), and can determine the degree of deterioration of the ink sending unit 420 between a new state and a faulty state, as shown in FIG. 14.

[0077] Furthermore, the ink level measuring device 440 can also predict the degree of deterioration and the time of failure by monitoring the level and the rate of change of the level relative to a reference level over time, as shown in Fig. 14. Since the degree of deterioration can be predicted in this way, for example, by predicting the time when 80% deterioration will occur and replacing the deteriorated parts at the predicted time of 80% deterioration, it is possible to prevent the ink delivery unit 420 from breaking down and the ink jet printer 100 from stopping. In other words, by replacing the deteriorated parts before a failure occurs, it is possible to prevent the ink delivery unit 420 from breaking down and the ink jet printer 100 from stopping.

[0078] In this case, the measuring unit 447 functions as a judgment unit that judges the state of the liquid delivery unit 420, but the control unit 90 may be configured to function as a judgment unit that judges the state of the liquid delivery unit 420 based on the liquid level height determined by the measuring unit 447.

[0079] As described above, in this embodiment, the inkjet printer 100 includes an ink level measuring device 440. The ink level measuring device 440 includes a sensor 445 that detects, as a continuous value, a change in a physical quantity (magnetic flux density) accompanying a change in the level of the ink I in the second subtank 431, and a measuring unit 447 that determines the level based on the detected physical quantity.

[0080] According to this embodiment configured in this manner, the sensor 445 detects the change in physical quantity (magnetic flux density) accompanying the change in the liquid level of the ink I in the second subtank 431 as a continuous value, so that the ink liquid level can be measured continuously and with high accuracy.

[0081] Furthermore, the ink level measuring device 440 includes a magnetic body 446 disposed adjacent to the upper side of the sensor 445, so that the ink level can be measured with even higher accuracy.

[0082] Furthermore, in the ink level measuring device 440, the measuring unit 447 determines the state of the liquid delivery unit 420 based on the liquid level height relative to a reference height and the rate of change of the liquid level height, so that it is possible to determine whether the liquid delivery unit 420 is malfunctioning and also to predict the degree of deterioration and the time of malfunction.

[0083] The above-mentioned embodiments are merely examples of the embodiment of the present invention, and the technical scope of the present invention should not be interpreted as being limited by these. In other words, the present invention can be embodied in various forms without departing from the gist or main characteristics of the present invention. [Explanation of symbols]

[0084] 10. Conveyor 20 Supply section 30 Discharge section 40 Ink supply unit 50 Head Module 70 Operation display section 80 Input / Output Interface 90 Control section 100 Inkjet Printer 200 External device 410 1st Subtank Section 411 First Subtank 420 Liquid delivery section 421 Tank Supply Line 422 Degassing Module 423 Pump 424 Valve 425 Filter 430 Second Subtank Section 431 Second Subtank 432 Pneumatic Pump 433 Head supply channel 440 Ink Level Measuring Device 441 Float 442 Information Department 443, 444 Magnet 445 Sensor 446 Magnetic material 447 Measurement Division

Claims

1. a detection unit that detects a change in a physical quantity accompanying a change in the liquid level of the ink in the container as a continuous value; A measuring unit that determines the liquid level based on the detected physical quantity; Equipped with Ink level measuring device.

2. The detection unit and a magnetic body fixed to the container; a float having a magnet, the float moving in the container in response to a change in the liquid level; Equipped with the detection unit is a sensor that detects a change in magnetic flux density caused by the magnet as the continuous value, The magnetic body and the sensor are arranged such that the sensor is located between the magnetic body and the magnet.

2. The ink level measuring device according to claim 1.

3. a determination unit that determines a state of an ink supply path to the container based on the liquid level or a rate of change of the liquid level relative to a reference level, 2. The ink level measuring device according to claim 1.

4. When the width of the magnet in a direction perpendicular to the liquid level direction is a and the maximum distance between the magnet and the sensor in the liquid level direction is b, the magnetic body is disposed within a periphery of the sensor within 2×a / b.

3. The ink level measuring device according to claim 2.

5. The magnetic body is disposed within a perimeter a / b of the sensor.

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

6. The width of the magnetic body in the orthogonal direction is 2×b / a or more.

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

7. The width of the magnetic body is 4×b / a or more.

7. The ink level measuring device according to claim 6.

8. the determining unit determines a state of the ink supply path based on the liquid level when the ink is supplied to the container for a predetermined period of time.

4. The ink level measuring device according to claim 3.

9. the determining unit determines a 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 period of time.

4. The ink level measuring device according to claim 3.

10. The ink supply path has a filter.

4. The ink level measuring device according to claim 3.

11. 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.

Images