Liquid droplet discharge apparatus, abnormality detection method for liquid droplet discharge apparatus, and program

Abstract

To provide a liquid droplet discharge apparatus, an abnormality detection method for the liquid droplet discharge apparatus, and a program capable of detecting an abnormality in a liquid feeding unit with a simple configuration.SOLUTION: A liquid droplet discharge apparatus 1 that discharges liquid from a nozzle of a liquid droplet discharge head 24a comprises: a liquid feeding unit 40 that feeds liquid to the liquid droplet discharge head 24a; and a determination unit 50. The liquid feeding unit 40 comprises a main tank 41 for storing liquid, a sub tank 42 for storing liquid supplied from the main tank 41, and a liquid flow path 43 connecting the main tank 41, the sub tank 42, and the liquid droplet discharge head 24a. The sub tank 42 includes a liquid level measuring unit LM for measuring a liquid level height therein. The determination unit 50 determines the presence / absence of an abnormality in the liquid feeding unit 40 on the basis of a measurement result of the liquid level measuring unit LM.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a droplet ejection device, a method for detecting an abnormality in a droplet ejection device, and a program. [Background technology]

[0002] Conventionally, there is known a droplet ejection device that ejects droplets onto the recording surface of a recording medium to record an image. The droplet ejection device includes a tank containing a liquid. The droplet ejection device also includes a liquid delivery unit that delivers the liquid from the tank to a droplet ejection head. The liquid delivered to the droplet ejection head is then ejected from a nozzle at an appropriate timing to form an image on the recording medium.

[0003] In particular, droplet ejection devices often use a circulation head that circulates the liquid from the head back to the tank. Using a circulation head prevents liquid that is not ejected from the nozzle from coming into contact with air and thickening, which can lead to ejection problems. It also prevents components in the liquid from settling and clogging the flow path, or the liquid from becoming unevenly concentrated.

[0004] However, continued circulation of the liquid can worsen the dispersion state of the components in the liquid. This can cause abnormalities in the liquid delivery section. For example, if the particle size of foreign matter in the liquid increases, the filter that removes the foreign matter can become clogged. When an abnormality occurs in the liquid delivery section, the flow rate of the liquid decreases, reducing image recording productivity. On the other hand, since images cannot be recorded on the recording medium while the liquid delivery section is being inspected, frequent inspections of the liquid delivery section will reduce image recording productivity. Therefore, it is necessary to properly detect abnormalities in the liquid delivery section and eliminate the abnormalities.

[0005] Therefore, for example, Patent Document 1 describes a configuration in which the flow rate of the liquid is kept constant and an abnormality in the ink supply path, including the filter, is detected from fluctuations in the measurement values ​​of pressure gauges placed before and after the object. Also, Patent Document 2 describes a configuration in which a pressure difference is kept constant and a clogged filter is detected from changes in the flow rate of the liquid. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5537988 [Patent Document 2] Patent No. 5486386 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the invention of Patent Document 1, the pressure gauge measurement value is affected by the pulsation of the pump that delivers liquid to the tank. Therefore, it is necessary to eliminate the effect of the pump pulsation, which poses the problem of making the configuration complicated. Furthermore, while the invention of Patent Document 2 can reduce the effect of the pump pulsation, it cannot detect abnormalities when the liquid level sensor breaks down.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a droplet ejection device that can detect an abnormality in a liquid delivery unit with a simple configuration, and a method and program for detecting an abnormality in a droplet ejection device. [Means for solving the problem]

[0009] In order to solve the above problems, the invention described in claim 1 is: A droplet ejection device that ejects liquid from a nozzle of a droplet ejection head, a liquid delivery unit that delivers liquid to the droplet ejection head; and a determination unit, the liquid delivery unit includes a main tank that stores a liquid, a sub-tank that stores the liquid supplied from the main tank, and a liquid flow path that connects the main tank, the sub-tank, and the droplet ejection head; the subtank is provided with a liquid level measuring unit that measures changes in the liquid level inside the subtank, The droplet ejection device is configured such that the determining unit determines whether or not there is an abnormality in the liquid delivery unit based on the measurement result of the liquid level measuring unit.

[0010] The invention described in claim 2 is the droplet ejection device described in claim 1, the sub-tank includes a first sub-tank provided upstream of the droplet ejection head in the liquid sending direction, and a second sub-tank provided downstream of the droplet ejection head in the liquid sending direction, the liquid flow path communicates with the main tank so that the liquid in the droplet ejection head can be returned; The liquid supply device includes a reflux section that creates a pressure difference between the first sub-tank and the second sub-tank to send liquid from the first sub-tank to the second sub-tank.

[0011] The invention described in claim 3 is the droplet ejection device described in claim 2, an acquisition unit that acquires a liquid level rise time and a liquid level fall time in the sub-tank from the liquid level measurement unit, The determination unit determines whether or not there is an abnormality in the liquid delivery unit by comparing the liquid level rise time and the liquid level fall time acquired by the acquisition unit with a predetermined allowable value.

[0012] The invention described in claim 4 is the droplet ejection device described in claim 3, The determining unit determines that a head filter of the droplet ejection head is abnormal if the liquid level fall time of the first sub-tank and the liquid level rise time of the second sub-tank are both greater than the predetermined allowable value.

[0013] The invention described in claim 5 is the droplet ejection device described in claim 3, the liquid flow path includes a removal unit that removes foreign matter from the liquid downstream of the main tank in the liquid sending direction and upstream of the first sub-tank in the liquid sending direction, When only the liquid level rise time of the first sub-tank is greater than the predetermined allowable value, the determining unit determines that the liquid level measuring unit or the removal unit of the first sub-tank is abnormal.

[0014] The invention described in claim 6 is the droplet ejection device described in claim 3, the determining unit determines that the liquid level measuring unit of the first sub-tank is abnormal when only the liquid level drop time of the first sub-tank is greater than the predetermined allowable value, If only one of the liquid level rise time of the second sub-tank and the liquid level fall time of the second sub-tank is greater than the predetermined allowable value, it is determined that the liquid level measuring unit of the second sub-tank has an abnormality.

[0015] The invention described in claim 7 is the droplet ejection device described in claim 1, When the determination unit determines that the liquid delivery unit has an abnormality, the determination unit determines whether the abnormality is gradual or sudden based on the measurement result of the liquid level measurement unit.

[0016] The invention described in claim 8 is the droplet ejection device described in claim 3, When the droplet ejection head is ejecting liquid, the determining unit corrects the predetermined allowable value in accordance with the ejection amount of the liquid.

[0017] The invention described in claim 9 is the droplet ejection device described in claim 8, The determining unit determines that the nozzle has an abnormality based on the measurement result of the liquid level measuring unit.

[0018] The invention described in claim 10 is the droplet ejection device described in claim 2, the liquid level measuring unit notifies the determining unit only when the liquid level in the sub-tank reaches a predetermined lower limit value; The determination unit determines whether or not there is an abnormality in the liquid delivery unit based on the cycle of the liquid level change in the subtank.

[0019] An eleventh aspect of the present invention is the droplet ejection device according to any one of the first to tenth aspects, The liquid delivery control unit is configured to stop delivery of liquid by the liquid delivery unit when the determination unit determines that the liquid delivery unit has an abnormality.

[0020] The invention described in claim 12 is a liquid delivery unit that delivers liquid to the droplet discharge head; the liquid delivery unit includes a main tank that stores a liquid, a sub-tank that stores the liquid supplied from the main tank, and a liquid flow path that connects the main tank, the sub-tank, and the droplet ejection head; the subtank is provided with a liquid level measuring unit that measures changes in the liquid level inside the subtank, A method for detecting an abnormality in a droplet ejection device that ejects liquid from a nozzle of the droplet ejection head, comprising: The method further includes a determination step of determining whether or not there is an abnormality in the liquid delivery section based on the measurement result of the liquid level measurement section.

[0021] The invention described in claim 13 is a droplet ejection head that ejects liquid from a nozzle; a liquid delivery unit that delivers liquid to the droplet discharge head, the liquid delivery unit includes a main tank that stores a liquid, a sub-tank that stores the liquid supplied from the main tank, and a liquid flow path that connects the main tank, the sub-tank, and the droplet ejection head; The subtank is a program that causes a droplet ejection device having a liquid level measurement unit that measures changes in the liquid level inside the subtank to function as a determination unit, The determination unit determines whether or not there is an abnormality in the liquid delivery unit based on the measurement result of the liquid level measurement unit. [Effects of the Invention]

[0022] According to the present invention, an abnormality in the liquid delivery section can be detected with a simple configuration. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a side cross-sectional view of an inkjet recording apparatus. [Figure 2] FIG. 2 is a schematic diagram of a liquid delivery section. [Figure 3] FIG. 1 is a block diagram of an inkjet recording apparatus. [Figure 4A]10 is a graph showing the change over time in the liquid level in the first sub-tank when a clog occurs in the head filter. [Figure 4B] 10 is a graph showing the change over time in the liquid level in the second sub-tank when a clog occurs in the head filter. [Figure 5A] 10 is a graph showing the change over time in the liquid level in the first sub-tank when a blockage occurs in the removal section. [Figure 5B] 10 is a graph showing the change over time in the liquid level in the second sub-tank when a blockage occurs in the removal section. [Figure 6] 10 is a table summarizing the relationship between the occurrence of abnormalities in the liquid delivery unit according to the first embodiment and changes in the liquid level rise time and liquid level fall time of each sub-tank. [Figure 7] 10 is a table summarizing the relationship between the occurrence of abnormalities in the liquid delivery unit according to the second embodiment and changes in the liquid level rise time and liquid level fall time of each sub-tank. [Figure 8A] 10 is a graph showing the change over time in the liquid level in the first sub-tank during normal ejection. [Figure 8B] 10 is a graph showing the change over time in the liquid level of the second sub-tank during normal ejection. [Figure 9A] 10 is a graph showing the change over time in the liquid level in the first sub-tank when a nozzle blockage occurs. [Figure 9B] 10 is a graph showing the change over time in the liquid level in the second sub-tank when a nozzle blockage occurs. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, droplet ejection devices according to embodiments of the present invention will be described in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples. In the following description, components having the same functions and configurations will be given the same reference numerals, and their description will be omitted.

[0025] [First embodiment] [Overall configuration of inkjet recording device] 1 is a side cross-sectional view showing the main configuration of an inkjet recording apparatus 1, which is one embodiment of the droplet ejection device of the present invention. The inkjet recording apparatus 1 includes a paper feed unit 10, an image forming unit 20, a paper discharge unit 30, a liquid delivery unit 40 (see FIG. 2), a control unit 50, and a notification unit 60 (both of which are shown in FIG. 3).

[0026] (Paper feed section) The paper feed unit 10 stores recording media P before image formation. The paper feed unit 10 transports the recording media P to the image forming unit 20 under the control of the control unit 50. The paper feed unit 10 includes a paper feed tray 11, a transport unit 12, and the like.

[0027] {Paper feed tray} The paper feed tray 11 is a plate-like member that stores recording media P. The paper feed tray 11 is provided so that one or more recording media P can be placed on it. The paper feed tray 11 moves up and down depending on the amount of recording media P placed on it. Depending on the direction of the up and down movement, the paper feed tray 11 is held at a position where the top recording medium P is transported by the transport unit 12.

[0028] {Transportation section} The conveying unit 12 conveys the recording medium P from the paper feed tray 11 to the image forming unit 20. The conveying unit 12 includes a conveying mechanism. The conveying mechanism drives a belt 123 to convey the recording medium P on the belt 123. The belt 123 is loop-shaped. The inner side of the belt 123 is supported by a plurality of rollers 121 and 122.

[0029] The conveying unit 12 includes a supply unit. The supply unit delivers the top recording medium P placed on the paper feed tray 11 onto the belt 123. The conveying unit 12 conveys the recording medium P along the belt 123 by the supply unit.

[0030] (Image forming section) The image forming unit 20 cooperates with the liquid supply unit 40 to perform a recording operation on the recording medium P under the control of the control unit 50. The image forming unit 20 includes an image forming drum 21, a delivery unit 22, a paper heating unit 23, a head unit 24, an irradiation unit 25, a delivery unit 26, and the like.

[0031] {Image forming drum} The image forming drum 21 carries the recording medium P along its cylindrical outer circumferential surface and transports the recording medium P as it rotates. The transport surface of the image forming drum 21 faces the paper heating section 23, the head unit 24, and the irradiation section 25. The image forming section 20 performs an image formation process on the recording medium P transported by the image forming drum 21.

[0032] {Delivery unit} The delivery unit 22 is provided at a position interposed between the transport section 12 and the image forming drum 21. The delivery unit 22 includes a claw portion 221, a delivery drum 222, and the like.

[0033] The claw portion 221 is a cylindrical member that holds one end of the recording medium P conveyed by the conveying unit 12. The delivery drum 222 is a member that guides the recording medium P held by the claw portion 221.

[0034] The delivery unit 22 picks up the recording medium P on the conveying section 12 with the claw portion 221 and moves it along the outer circumferential surface of the delivery drum 222. The delivery unit 22 delivers the recording medium P to the image forming drum 21 by this operation.

[0035] {Paper heating section} The paper heating unit 23 includes, for example, an electric heating wire. The paper heating unit 23 generates heat in response to the passage of electricity. The paper heating unit 23 is controlled by the control unit 50. The paper heating unit 23 generates heat so that the recording medium P passing nearby reaches a predetermined temperature. The paper heating unit 23 is located near the outer circumferential surface of the image forming drum 21 and is positioned upstream of the head unit 24 in the transport direction of the recording medium P.

[0036] A temperature sensor (not shown) is provided near the paper heating unit 23. The control unit 50 uses the temperature sensor to detect the temperature near the paper heating unit 23. The control unit 50 controls the heat generation of the paper heating unit 23 based on the detected temperature.

[0037] {Head Unit} The head units 24 form an image by ejecting ink onto the recording medium P. The head units 24 are provided corresponding to the colors C (cyan), M (magenta), Y (yellow), and K (black). In FIG. 1, the head units 24 corresponding to the colors Y, M, C, and K are provided in this order from upstream in the transport direction.

[0038] The head units 24 of this embodiment are arranged in a plurality in the width direction, each having a length (width) sufficient to cover the entire recording medium P. In other words, the inkjet recording apparatus 1 of this embodiment is a line head type. The head unit 24 is configured by arranging a plurality of inkjet heads 24a (see FIG. 2, etc.), which are droplet ejection heads, in the width direction.

[0039] The number of head units 24 provided in the image forming section 20 may be three or less, or five or more. Also, a single inkjet head 24a may constitute a head unit 24. Also, the inkjet recording device 1 may be a serial head type that forms an image by scanning a head unit 24, whose width is shorter than that of the recording medium P, in the width direction.

[0040] The ink ejected by the head unit 24 is, for example, ultraviolet curable ink. The ultraviolet curable ink is a gel ink that changes phase between a gel state and a liquid (sol) state depending on the temperature when not irradiated with ultraviolet light from the irradiation unit 25. The ultraviolet curable ink has a phase change temperature of, for example, about 40 to 100°C, and is uniformly liquefied (solized) when heated to or above the phase change temperature. On the other hand, the ultraviolet curable ink gels at about normal room temperature, i.e., about 0 to 30°C.

[0041] [Inkjet head] The inkjet head 24a has an inlet, which is an ink inlet. The inkjet head 24a ejects ink supplied from the inlet from nozzles provided on its underside. The inkjet head 24a also has an outlet, which is an ink outlet for ejected ink. The inkjet head 24a also has a head filter F (see FIG. 2) that filters the ink, located downstream of the inlet in the liquid sending direction and upstream of the nozzle in the liquid sending direction.

[0042] {Irradiation unit} The irradiation unit 25 includes, for example, a fluorescent tube such as a low-pressure mercury lamp. The irradiation unit 25 emits energy rays such as ultraviolet light by emitting light from the fluorescent tube. The irradiation unit 25 is provided near the outer circumferential surface of the image forming drum 21. The irradiation unit 25 is also provided so as to be located downstream of the head unit 24 in the transport direction of the recording medium P. The irradiation unit 25 irradiates the recording medium P onto which ink has been ejected with energy rays. The ink on the recording medium P is cured by the action of the energy rays.

[0043] The fluorescent tube that emits ultraviolet light is not limited to a low-pressure mercury lamp. The fluorescent tube may be a mercury lamp with an operating pressure of, for example, several hundred Pa to 1 MPa. The fluorescent tube may also be a light source that can be used as a germicidal lamp, such as a cold cathode tube, an ultraviolet laser light source, a metal halide lamp, or a light-emitting diode. Among these, it is desirable that the fluorescent tube be a light source that can irradiate ultraviolet light with higher illuminance and is energy-saving. The fluorescent tube may be, for example, a light-emitting diode.

[0044] The energy rays are not limited to ultraviolet rays, and may be any energy rays that have the property of curing the ink depending on the properties of the ink. The light source may also be replaced depending on the energy rays.

[0045] In addition, although the above example illustrates a case where the head unit 24 ejects ultraviolet curable ink, the present invention is not limited to this. The ink ejected by the head unit 24 may be water-based ink or ink with other physical properties.

[0046] {Delivery Department} The delivery unit 26 includes a transport mechanism. The transport mechanism drives a ring-shaped belt 263, the inside of which is supported by a plurality of rollers 261 and 262, to transport the recording medium P. The delivery unit 26 includes a cylindrical delivery roller 264. The delivery roller 264 delivers the recording medium P from the image forming drum 21 to the transport mechanism. The delivery unit 26 transports the recording medium P delivered onto the belt 263 by the delivery roller 264, and sends it out to the paper discharge unit 30.

[0047] (Paper ejection section) The paper discharge unit 30 discharges the recording medium P on which an image has been formed in the image forming unit 20. The paper discharge unit 30 includes a plate-shaped paper discharge tray 31. The recording medium P sent out from the image forming unit 20 by the delivery unit 26 is placed on the paper discharge tray 31. The paper discharge unit 30 stores the recording medium P until the user removes it.

[0048] (liquid delivery section) Fig. 2 is a schematic diagram of the liquid delivery unit 40. Note that Fig. 2 shows only one inkjet head 24a, omitting the multiple inkjet heads 24a. The liquid delivery unit 40 includes the inkjet head 24a, a main tank 41, a sub-tank 42, a liquid flow path 43, and the like.

[0049] {Main Tank} The main tank 41 contains ink of each color that is supplied to each part of the liquid delivery unit 40. Although omitted in FIG. 2, a main tank 41 is provided for each ink color. The ink is supplied to the inkjet head 24a by a supply pump 4311, which will be described later, via a first liquid flow path 431, a first sub-tank 421, and a second liquid flow path 432. The main tank 41 is replaceable as a whole, and is formed to be detachable from the first liquid flow path 431 regardless of the operating status of the supply pump 4311.

[0050] {Subtank} The sub-tank 42 includes, for example, a first sub-tank 421 and a second sub-tank 422. The sub-tank 42 stores ink therein. The capacity of the sub-tank 42 is less than or approximately the same as that of the main tank 41.

[0051] Each subtank 42 is provided with a liquid level measurement unit LM. The liquid level measurement unit LM is, for example, a float sensor, and acquires measurement data relating to the liquid level position of the ink in each subtank 42 and outputs it to the control unit 50. The control unit 50 acquires the remaining amount of ink in each subtank 42 from the measurement data, and appropriately sends ink from the main tank 41 or the first subtank 421 located upstream in the liquid sending direction. The control unit 50 also acquires the liquid level rise time and liquid level fall time in each subtank 42 from the measurement data.

[0052] In the following description, for the sake of distinction, the liquid level measuring unit LM provided in the first sub-tank 421 will be referred to as the first liquid level measuring unit LM1, and the liquid level measuring unit LM provided in the second sub-tank 422 will be referred to as the second liquid level measuring unit LM2.

[0053] The subtank 42 is also provided with an ink heating unit (not shown) that maintains the ink inside at an appropriate temperature. The ink heating unit is made up of a heater, a heat transfer member that transfers heat from the heater, and the like. The heater that makes up the ink heating unit is, for example, an electric heating wire that generates Joule heat when electricity is applied. The heat transfer member that makes up the ink heating unit is made up of a material with high thermal conductivity, such as a heat conduction plate made of various metals (alloys).

[0054] [1st subtank, 2nd subtank] The first sub-tank 421 is located upstream of the inkjet head 24a in the liquid sending direction. The first sub-tank 421 temporarily stores ink supplied from the main tank 41. The provision of the first sub-tank 421 in the liquid sending unit 40 reduces pressure changes caused by pulsation when the supply pump 4311 supplies ink from the main tank 41. The second sub-tank 422 is located downstream in the liquid sending direction. The second sub-tank 422 temporarily stores ink collected from the inkjet head 24a.

[0055] Each sub-tank 42 is provided with an atmosphere communication passage (not shown) that communicates with the atmosphere. The atmosphere communication passage is provided with an air pressure pump that can suck air from each sub-tank 42 and reduce the pressure under the control of the control unit 50, thereby controlling the pressure inside each sub-tank 42.

[0056] In particular, the control unit 50 constantly creates a pressure difference between the first subtank 421 and the second subtank 422 by, for example, using an air pressure pump to send air from the second subtank 422 to the first subtank 421. Through this control, the control unit 50 constantly sends liquid from the first subtank 421 to the second subtank 422.

[0057] {Liquid flow path} The liquid flow path 43 is an ink flow path that connects the main tank 41 to the inkjet head 24a so as to allow the ink to return. The liquid flow path 43 includes a first liquid flow path 431, a second liquid flow path 432, a third liquid flow path 433, and a fourth liquid flow path 434. The liquid flow path 43 is preferably ink-resistant, and has a hollow, annular tube structure.

[0058] [First liquid flow path] The first liquid flow path 431 is a flow path that connects the main tank 41 and the first sub-tank 421. In the first liquid flow path 431, a supply pump 4311 and a removal unit 4312 are provided.

[0059] When the control unit 50 detects, as a result of measurement by the first liquid level measurement unit LM1, that the liquid level in the first subtank 421 is at a predetermined lower limit, it drives the supply pump 4311. The amount of liquid sent per unit time by the supply pump 4311 is greater than the amount of liquid sent from the first subtank 421 to the second subtank 422. Therefore, while the supply pump 4311 is running, the liquid level in the first subtank 421 continues to rise. The control unit 50 continues to send ink from the main tank 41 until the first liquid level measurement unit LM1 measures that the liquid level in the first subtank 421 has reached a predetermined upper limit.

[0060] <Removal part> The removal unit 4312 is a member that removes foreign matter from the ink flowing through the first liquid flow path 431. The removal unit 4312 is, for example, a flow path filter or a degassing module. The flow path filter is formed, for example, from a mesh-like porous material such as metal or resin, and has a mesh of a predetermined size. The degassing module removes gas dissolved in the ink that has passed through it. The degassing module includes, for example, a gas-permeable membrane that is made airtight and then decompressed by sucking in the air inside. When the ink comes into contact with the gas-permeable membrane, the pressure difference causes the dissolved gas in the ink to pass through the gas-permeable membrane.

[0061] [Second liquid flow path, third liquid flow path] The second liquid flow path 432 is a flow path that connects the first sub-tank 421 and the inlet of the inkjet head 24a, and the third liquid flow path 433 is a flow path that connects the second sub-tank 422 and the outlet of the inkjet head 24a.

[0062] [Fourth liquid flow path] The fourth liquid flow path 434 is a flow path that connects the second sub-tank 422 and the main tank 41. A liquid feed pump 4341 is provided in the fourth liquid flow path 434.

[0063] <Liquid transfer pump> The liquid feed pump 4341 feeds the liquid in the second subtank 422 to the main tank 41. When the control unit 50 detects, as a result of measurement by the second liquid level measurement unit LM2, that the liquid level in the second subtank 422 is at a predetermined upper limit, the control unit 50 drives the liquid feed pump 4341. The amount of liquid fed per unit time by the liquid feed pump 4341 is greater than the amount of liquid fed from the first subtank 421 to the second subtank 422. Therefore, while the liquid feed pump 4341 is driven, the liquid level in the second subtank 422 continues to decrease. The control unit 50 causes the liquid feed pump 4341 to feed ink until the second liquid level measurement unit LM2 measures that the liquid level in the second subtank 422 has reached a predetermined lower limit.

[0064] (Control unit) Fig. 3 is a block diagram showing the internal configuration of the inkjet recording apparatus 1. A control unit 50 controls each unit constituting the inkjet recording apparatus 1. As shown in Fig. 3, the control unit 50 is connected to each unit constituting the inkjet recording apparatus 1. The control unit 50 includes a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), etc.

[0065] The CPU reads out various programs, data, etc. corresponding to the processing content from a storage device such as a ROM and executes them. The CPU controls the operation of each part of the inkjet recording device 1 according to the processing content executed. The RAM temporarily stores various programs, data, etc. processed by the CPU. The ROM stores various programs, data, etc. read out by the CPU, etc.

[0066] In particular, the control unit 50 functions as a determination unit that executes an abnormality detection process and determines whether or not an abnormality exists in the liquid delivery unit 40 based on the measurement results of the liquid level measurement unit LM. A detailed description of the abnormality detection process will be given later. As described above, the control unit 50 also functions as a reflux unit that creates a pressure difference between the first sub-tank 421 and the second sub-tank 422 to deliver liquid from the first sub-tank 421 to the second sub-tank 422. The control unit 50 also functions as an acquisition unit that acquires the liquid level rise time and liquid level fall time in each sub-tank 42 from the measurement results of the liquid level measurement unit LM.

[0067] (Notification Department) The notification unit 60 notifies various pieces of information under the control of the control unit 50. The notification unit 60 is, for example, a display unit having a screen or a speaker that emits sound. Alternatively, the notification unit 60 may be a communication unit or the like that can communicate with other devices via a predetermined network.

[0068] [Abnormality detection processing] The abnormality detection process in the inkjet recording apparatus 1 configured as above will be described with reference to FIG. 4A and subsequent figures.

[0069] The ROM of the control unit 50 stores allowable values ​​for the time it takes for the liquid level to rise or fall from the time the liquid level reaches the upper or lower limit after reaching the lower or upper limit in each subtank 42. These allowable values ​​are calculated in advance, for example, based on experiments conducted before shipping the inkjet recording apparatus 1.

[0070] The control unit 50 executes the abnormality detection process at a predetermined timing, such as during standby, when the liquid level in the first sub-tank 421 and the second sub-tank 422 has reached the lower limit and upper limit values ​​at least once since the previous abnormality detection process.

[0071] First, the control unit 50 acquires the measurement results of the first liquid level measurement unit LM1 and the second liquid level measurement unit LM2. Then, the control unit 50 detects whether or not there is an abnormality in the liquid delivery unit 40 by comparing the liquid level rise time and liquid level fall time of the first sub-tank 421 and the second sub-tank 422 with the allowable values ​​stored in the ROM.

[0072] (Head filter abnormality) 4A and 4B show graphs relating to the transition of the liquid level in the first sub-tank 421 and the second sub-tank 422 when an abnormality (e.g., clogging) occurs in the head filter F. In the following figures, the horizontal axis represents time and the vertical axis represents the liquid level. In the graphs of FIGS. 4A to 5B, the dotted lines represent the transition of the liquid level when no abnormality occurs in the liquid delivery unit 40. In the following graphs, the straight lines represent the transition of the liquid level when an abnormality occurs in the liquid delivery unit 40.

[0073] If the head filter F is clogged, it takes longer to transfer the liquid from the first sub-tank 421 to the second sub-tank 422. Therefore, as shown in Figures 4A and 4B, both the time it takes for the liquid level in the first sub-tank 421 to fall and the time it takes for the liquid level in the second sub-tank 422 to rise are longer than normal.

[0074] (When the liquid level measurement part is abnormal) Furthermore, if an abnormality occurs in the liquid level measuring unit LM, the way in which the liquid level rise time and the liquid level fall time change will differ depending on the liquid level measuring unit LM in which the abnormality occurred and the nature of the abnormality. For example, if the first liquid level measuring unit LM1 is no longer able to detect the upper limit value of the liquid level height in the first subtank 421, only the liquid level rise time of the first subtank 421 will be longer than normal. Also, if the first liquid level measuring unit LM1 is no longer able to detect the lower limit value of the liquid level height in the first subtank 421, only the liquid level fall time of the first subtank 421 will be longer than normal. Also, if the second liquid level measuring unit LM2 is no longer able to detect the upper limit value of the liquid level height in the second subtank 422, only the liquid level rise time of the second subtank 422 will be longer than normal. Furthermore, when the second liquid level measuring unit LM2 is no longer able to detect the lower limit of the liquid level in the second sub-tank 422, only the time it takes for the liquid level in the second sub-tank 422 to fall becomes longer than normal.

[0075] (When the removal part is abnormal) 5A and 5B show graphs relating to the transition of the liquid level in the first sub-tank 421 and the second sub-tank 422 when an abnormality (e.g., clogging) occurs in the removal unit 4312. When an abnormality occurs in the removal unit 4312, it takes longer for the liquid to be transferred from the main tank 41 to the first sub-tank 421. Therefore, as shown in FIGS. 5A and 5B, only the time it takes for the liquid level in the first sub-tank 421 to rise becomes longer than normal.

[0076] As described above, when the first liquid level measuring unit LM1 is no longer able to detect the upper limit value of the liquid level height in the first subtank 421, or when a blockage occurs in the removal unit 4312, only the time for the liquid level to rise in the first subtank 421 becomes longer than normal. Therefore, when only the time for the liquid level to rise in the first subtank 421 becomes longer than normal, the control unit 50 determines that at least one of the first liquid level measuring unit LM1 and the removal unit 4312 has an abnormality.

[0077] If it is determined as a result of the comparison with the allowable value that the liquid delivery unit 40 has an abnormality, the control unit 50 functions as a liquid delivery control unit that stops the delivery of liquid by the liquid delivery unit 40. Then, the control unit 50 notifies the occurrence of an abnormality in the liquid delivery unit 40 via the notification unit 60. With this configuration, it is possible to prevent ink from overflowing from the subtank 42.

[0078] It is more preferable that the time notification unit 60 notifies whether an abnormality has occurred in any of the components of the liquid delivery unit 40 based on the determination result of the control unit 50.

[0079] [Effects of the first embodiment] Fig. 6 shows a table summarizing the relationship between the type of abnormality in the liquid delivery unit 40 and changes in the liquid level rise time and liquid level fall time of each sub-tank 42. As shown in Fig. 6, the liquid level rise time and liquid level fall time of each sub-tank 42 change depending on the type of abnormality in the liquid delivery unit 40. Therefore, the control unit 50 can detect an abnormality in the liquid delivery unit 40 with a simple configuration of acquiring the liquid level rise time and liquid level fall time of the sub-tank 42. Furthermore, with this configuration, even if an abnormality occurs in the liquid level measurement unit LM, the abnormality can be detected.

[0080] [Second embodiment] Next, an abnormality detection process in the liquid delivery unit 40 of the inkjet recording apparatus 1 according to the second embodiment will be described. The inkjet recording apparatus 1 according to the second embodiment differs from the first embodiment in that the liquid level measurement unit LM is configured to detect only the lower limit value of the liquid level height of the subtank 42.

[0081] Specifically, when the control unit 50 receives a signal from the first liquid level measuring unit LM1 that detects that the liquid level in the first sub-tank 421 is at the lower limit, the control unit 50 drives the supply pump 4311. The control unit 50 drives the supply pump 4311 for a predetermined period of time, thereby setting the liquid level in the first sub-tank 421 to the upper limit. Then, the control unit 50 stops driving the supply pump 4311 after the predetermined period of time has elapsed.

[0082] Furthermore, when the control unit 50 receives a signal from the second liquid level measuring unit LM2 that detects that the liquid level in the second subtank 422 is at the lower limit, it stops driving the liquid feed pump 4341. The control unit 50 sets the liquid level in the second subtank 422 to the upper limit by feeding the liquid from the first subtank 421 to the second subtank 422 for a predetermined period of time while the driving of the liquid feed pump 4341 is stopped. Then, the control unit 50 resumes driving the liquid feed pump 4341 after the predetermined period of time has elapsed.

[0083] The control unit 50 compares the cycle of the liquid level change with a predetermined tolerance value when detecting the presence or absence of an abnormality in the liquid delivery unit 40 according to the second embodiment. In other words, the control unit 50 compares the time from when the liquid level measurement unit LM detects that the liquid level in the corresponding subtank 42 is at the lower limit value until when it detects that the liquid level has again reached the lower limit value with the predetermined tolerance value.

[0084] 7 shows a table summarizing the relationship between the presence or absence of an abnormality in the liquid delivery unit 40 according to the second embodiment and the period of change in the liquid level of each sub-tank 42. As shown in FIG. 7, even if the liquid level measuring unit LM is configured to detect only the lower limit value of the liquid level height of the sub-tank 42, the control unit 50 can determine the presence or absence of an abnormality in the liquid delivery unit 40 based on the period of change in the liquid level of the sub-tank 42.

[0085] [Other configurations] Although the present invention has been specifically described above based on the embodiments thereof, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention as defined in the claims and their equivalents.

[0086] For example, in the first and second embodiments, the abnormality determination process in the liquid delivery unit 40 during standby has been described, but the timing for executing the abnormality determination process is not limited to during standby. That is, even during image formation processing, it is possible to determine whether or not there is an abnormality in the liquid delivery unit 40.

[0087] 8A and 8B are graphs showing the transition of the liquid level in the first sub-tank 421 and the second sub-tank 422 during image formation processing. Note that in Figures 8A to 8B, the dotted line graphs show the transition of the liquid level during standby.

[0088] 8A, during image formation processing, i.e., while ink is being ejected, the time it takes for the liquid level in the first sub-tank 421 to fall is shorter than during standby, depending on the amount of ink ejected. Also, as shown in Fig. 8B, during ink ejection, the time it takes for the liquid level in the second sub-tank 422 to rise is longer than during standby, depending on the amount of ink ejected.

[0089] Therefore, when performing the abnormality determination process during the image formation process, it is preferable to correct the allowable value of the liquid level fall time in the first sub-tank 421 and the allowable value of the liquid level rise time in the second sub-tank 422. In particular, it is more preferable that the control unit 50 vary the amount of correction depending on the amount of ink ejected.

[0090] Furthermore, during image formation processing, it is possible to determine whether or not there is an abnormality (e.g., clogging) in the nozzles of the inkjet head 24a, not just in the liquid delivery unit 40. Graphs showing the transition of the liquid level in the first sub-tank 421 and the second sub-tank 422 when an abnormality occurs in the nozzles are shown in Figures 9A and 9B. In Figures 9A and 9B, the dashed-dotted line graphs show the transition of the liquid level during image formation processing when no abnormality occurs in the nozzles.

[0091] 9A, when a nozzle malfunctions, the time it takes for the liquid level to fall in the first sub-tank 421 is shorter than during normal standby and longer than during normal image formation. Also, as shown in FIG. 9B, the time it takes for the liquid level to rise in the second sub-tank 422 is longer than during normal standby and shorter than during normal image formation.

[0092] In addition, although the above description has been given of an example in which the droplet ejection device is an inkjet recording device 1 that ejects ink, the present invention is not limited to this. In other words, the present invention may be applied to various types of droplet ejection devices that eject droplets of liquid other than ink from nozzles.

[0093] Furthermore, although the above example illustrates a configuration in which the liquid delivery unit 40 includes two sub-tanks 42, the present invention is not limited to this. That is, even if the liquid delivery unit 40 includes only the first sub-tank 421, the abnormality detection process can be performed.

[0094] Furthermore, when the control unit 50 determines that the liquid delivery unit 40 has an abnormality, it may further determine whether the occurrence of the abnormality is gradual or sudden. Specifically, for example, the control unit 50 can determine whether the occurrence of the abnormality is gradual or sudden, based on whether the deviation from the allowable value is gradual for multiple liquid level rise times and liquid level fall times in the target subtank 42 immediately before it is determined that the abnormality has occurred. By determining whether the occurrence of the abnormality is gradual or sudden, the location of the abnormality can be identified with higher accuracy.

[0095] In particular, if only the time taken for the liquid level to rise in the first sub-tank 421 is greater than the predetermined allowable value and the abnormality occurs suddenly, it can be determined that an abnormality has occurred in the first liquid level measuring unit LM1. On the other hand, if only the time taken for the liquid level to rise in the first sub-tank 421 is greater than the predetermined allowable value and the abnormality occurs gradually, it can be determined that an abnormality has occurred in the removal unit 4312.

[0096] Although examples have been disclosed in which a hard disk or a semiconductor nonvolatile memory is used as a computer-readable medium for the program according to the present invention, the present invention is not limited to this. Other computer-readable media include portable recording media such as CD-ROMs. Furthermore, carrier waves are also applicable as a medium for providing the program data according to the present invention via a communication line. [Explanation of symbols]

[0097] 1. Inkjet recording device (droplet ejection device) 24a Inkjet head (droplet ejection head) 40 Liquid delivery section 41 Main Tank 42 Subtank 421 1st Subtank 422 Second Subtank 43 Liquid flow path 4312 Removal section 50 control unit (reflux unit, determination unit, acquisition unit, liquid transfer control unit) Front head filter LM liquid level measurement section

Claims

1. A droplet ejection device that ejects liquid from a nozzle of a droplet ejection head, a liquid delivery unit that delivers liquid to the droplet ejection head; and a determination unit, the liquid delivery unit includes a main tank that stores a liquid, a sub-tank that stores the liquid supplied from the main tank, and a liquid flow path that connects the main tank, the sub-tank, and the droplet ejection head; the subtank is provided with a liquid level measuring unit that measures changes in the liquid level inside the subtank, The droplet ejection device is configured such that the determining unit determines whether or not there is an abnormality in the liquid delivery unit based on the measurement result of the liquid level measuring unit.

2. the sub-tank includes a first sub-tank provided upstream of the droplet ejection head in the liquid sending direction, and a second sub-tank provided downstream of the droplet ejection head in the liquid sending direction, the liquid flow path communicates with the main tank so that the liquid in the droplet ejection head can be returned; The droplet ejection device according to claim 1 , further comprising a reflux section that sends liquid from the first sub-tank to the second sub-tank by creating a pressure difference between the first sub-tank and the second sub-tank.

3. an acquisition unit that acquires a liquid level rise time and a liquid level fall time in the sub-tank from the liquid level measurement unit, The droplet ejection device according to claim 2 , wherein the determination unit determines whether or not there is an abnormality in the liquid delivery unit by comparing the liquid level rise time and the liquid level fall time acquired by the acquisition unit with a predetermined allowable value.

4. The droplet ejection device according to claim 3, wherein the determination unit determines that the head filter of the droplet ejection head is abnormal if the liquid level drop time of the first sub-tank and the liquid level rise time of the second sub-tank are both greater than the predetermined allowable value.

5. the liquid flow path includes a removal unit that removes foreign matter from the liquid, the removal unit being located downstream of the main tank in the liquid sending direction and upstream of the first sub-tank in the liquid sending direction; The droplet ejection device according to claim 3 , wherein the determination unit determines that the liquid level measurement unit or the removal unit of the first sub-tank is abnormal if only the liquid level rise time of the first sub-tank is longer than the predetermined allowable value.

6. the determining unit determines that the liquid level measuring unit of the first sub-tank is abnormal if only the liquid level drop time of the first sub-tank is greater than the predetermined allowable value, A droplet ejection device as described in claim 3, wherein if either the liquid level rise time of the second sub-tank or the liquid level fall time of the second sub-tank is greater than the specified allowable value, it is determined that the liquid level measurement unit of the second sub-tank has an abnormality.

7. The droplet ejection device according to claim 3, wherein when the determination unit determines that the liquid delivery unit has an abnormality, the determination unit determines whether the abnormality is gradual or sudden based on the measurement results of the liquid level measurement unit.

8. 4. The droplet ejection device according to claim 3, wherein the determining unit corrects the predetermined allowable value in accordance with the amount of liquid ejected when the droplet ejection head is ejecting liquid.

9. The droplet ejection device according to claim 8 , wherein the determining unit determines that the nozzle is abnormal based on the measurement result of the liquid level measuring unit.

10. the liquid level measuring unit notifies the determining unit only when the liquid level in the sub-tank reaches a predetermined lower limit value; The droplet ejection device according to claim 2 , wherein the determining unit determines whether or not there is an abnormality in the liquid delivery unit based on a period of change in the liquid level in the subtank.

11. The droplet ejection device according to claim 1 , further comprising a liquid delivery control unit that stops delivery of liquid by the liquid delivery unit when the determination unit determines that the liquid delivery unit has an abnormality.

12. a liquid delivery unit that delivers liquid to the droplet discharge head; the liquid delivery unit includes a main tank that stores a liquid, a sub-tank that stores the liquid supplied from the main tank, and a liquid flow path that connects the main tank, the sub-tank, and the droplet ejection head; the subtank is provided with a liquid level measuring unit that measures changes in the liquid level inside the subtank, A method for detecting an abnormality in a droplet ejection device that ejects liquid from a nozzle of the droplet ejection head, comprising: An abnormality detection method comprising a determination step of determining whether or not there is an abnormality in the liquid delivery unit based on the measurement result of the liquid level measurement unit.

13. a droplet ejection head that ejects liquid from a nozzle; a liquid delivery unit that delivers liquid to the droplet discharge head, the liquid delivery unit includes a main tank that stores a liquid, a sub-tank that stores the liquid supplied from the main tank, and a liquid flow path that connects the main tank, the sub-tank, and the droplet ejection head; The subtank is a program that causes a droplet ejection device having a liquid level measurement unit that measures changes in the liquid level inside the subtank to function as a determination unit, The determination unit is a program that determines whether or not there is an abnormality in the liquid delivery unit based on the measurement results of the liquid level measurement unit.

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