Ink jet recording apparatus and abnormality detection method for ink flow path

Abstract

To facilitate apparatus repair by improving the accuracy of detecting abnormalities in an ink flow path, and detecting the abnormalities before they become severe.SOLUTION: An ink jet recording apparatus which includes an ink flow path that connects a recording head and an ink tank that stores ink to be supplied to the recording head, comprises: a pressure sensor which detects the liquid pressure within the ink flow path or the ink tank; a liquid feeding unit which applies pressure to the ink in the ink flow path or the ink tank and feeds the ink at a flow rate different from that during printing; and a determination unit which determines whether an abnormality exists in the ink flow path on the basis of the liquid pressure of the ink fed at the different flow rate.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an inkjet recording apparatus and a method for detecting an abnormality in an ink flow path.

Background Art

[0002] In an inkjet recording apparatus, as a method for detecting an abnormality (clogging, leakage) in an ink flow path, for example, as shown in Patent Document 1, a method of detecting using a pressure sensor disposed in a flow path or a tank is known.

[0003] The liquid ejection apparatus of Patent Document 1 is provided with a pressure sensor in an ink supply path for supplying ink from an ink tank to a recording head, and determines whether there is an abnormality in the flow path based on the pressure of the ink detected by the pressure sensor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in an inkjet recording apparatus, it is known that the pressure of the ink flowing through the ink flow path varies considerably (widely) depending on the amount of air in the ink, the temperature of the ink, etc., even when it is normal.

[0006] Therefore, in a structure such as the inkjet recording apparatus of Patent Document 1, in which the pressure value of the ink flowing through the flow path is simply detected and the abnormality of the flow path is determined based on the detected pressure value, the measured value has variations even if it is a normal value. Therefore, there is a problem that the pressure value of the measured abnormal state is buried within the range of the normal pressure value with such variations.

[0007] As a result, it has been found that with the conventional configuration, abnormalities cannot be detected until a serious abnormality appears in the ink flow path. Therefore, since maintenance of the apparatus can only be performed after a serious abnormality has occurred, there has been a problem that it becomes difficult to repair the apparatus.

[0008] The present invention has been made in view of such points, and an object thereof is to provide an inkjet recording apparatus and an ink flow path abnormality detection method capable of enhancing the detection accuracy of an abnormality in the ink flow path, detecting the abnormality before it becomes a serious abnormality, and facilitating the repair of the apparatus.

Means for Solving the Problems

[0009] One aspect of the inkjet recording apparatus according to the present invention is In an inkjet recording apparatus including an ink flow path connecting a recording head and an ink tank that stores ink to be supplied to the recording head, a pressure sensor that detects the hydraulic pressure in the ink flow path or in the ink tank, a liquid feeding unit that applies pressure to the ink in the ink flow path or in the ink tank and feeds the liquid at a flow rate different from that during printing, a determination unit that determines whether or not there is an abnormality in the ink flow path based on the hydraulic pressure of the ink fed at the different flow rate; and has a configuration including these.

[0010] One aspect of the method for detecting an abnormality in the ink flow path of the present invention is a method for detecting an abnormality in an ink flow path that supplies ink from an ink tank to a recording head, a liquid feeding step of feeding the ink in the ink flow path at a flow rate different from that during printing, a detection step of detecting the hydraulic pressure of the ink fed at the flow rate different from that during printing in the ink flow path, a determination step of comparing the detected hydraulic pressure with the hydraulic pressure of the ink normally fed at a flow rate different from that during printing to determine whether or not there is an abnormality in the ink flow path; and is configured to include these.

Advantages of the Invention

[0011] According to the present invention, the detection accuracy of abnormalities in the ink flow path can be improved, and the abnormalities can be detected before they become serious abnormalities, making it easy to repair the device.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0013] With reference to the accompanying drawings below, preferred embodiments of the present disclosure will be described in detail. In this specification and the drawings, components having substantially the same function are denoted by the same reference numerals, and redundant descriptions are omitted.

[0014] [Overall Configuration of Inkjet Recording Apparatus] Hereinafter, with reference to FIGS. 1 to 3, the configuration of an inkjet recording apparatus (hereinafter also referred to as a "recording apparatus") 1 according to an embodiment of the present invention will be described.

[0015] FIG. 1 is a diagram showing a schematic configuration of an inkjet recording apparatus 1 according to an embodiment of the present invention. The recording apparatus 1 includes a paper feeding unit 10, an image forming unit 20, a paper discharging unit 30, and a control unit 40. Under the control of the control unit 40, the recording apparatus 1 conveys the recording medium P stored in the paper feeding unit 10 to the image forming unit 20, ejects ink onto the recording medium P in the image forming unit 20 to record an image, and conveys the recording medium P on which the image is recorded to the paper discharging unit 30. Specifically, the recording apparatus 1 records a color image on the recording medium P by superimposing colors on the recording medium P for each of the four colors of yellow (Y), magenta (M), cyan (C), and black (K) at a predetermined number of recording gradations.

[0016] As the recording medium P, in addition to paper such as plain paper and coated paper, various media capable of fixing the ink landing on the surface, such as fabric or sheet-like resin, can be used.

[0017] The paper feeding unit 10 includes a paper feeding tray 11 for storing the recording medium P, and a medium supply unit 12 for conveying and supplying the recording medium P from the paper feeding tray 11 to the image forming unit 20. The medium supply unit 12 includes an annular belt supported inside by two rollers, and conveys the recording medium P from the paper feeding tray 11 to the image forming unit 20 by rotating the rollers with the recording medium P placed on the belt.

[0018] The image forming unit 20 includes a conveying unit 21, a delivery unit 22, a heating unit 23, a head unit 24, an irradiation unit 25, and a delivery unit 27.

[0019] The conveying unit 21 holds the recording medium P placed on the conveying surface of the cylindrical conveying drum 211. The conveying unit 21 conveys the recording medium P on the conveying drum 211 in the conveying direction along the conveying surface by rotating and circulating the conveying drum 211 around a rotation axis (cylindrical axis) extending in the width direction of the recording medium P.

[0020] The conveying drum 211 is provided with claw portions and an air intake portion (not shown) for holding the recording medium P on its conveying surface. The recording medium P is held on the conveying surface by having its end pressed by the claw portions and being attracted to the conveying surface by the air intake portion.

[0021] The delivery unit 22 is provided at a position between the medium supply unit 12 of the paper feeding unit 10 and the conveying unit 21. The delivery unit 22 holds and picks up one end of the recording medium P conveyed from the medium supply unit 12 with the swing arm portion 221, and delivers it to the conveying unit 21 via the delivery drum 222.

[0022] The heating unit 23 is provided between the arrangement position of the delivery drum 222 and the arrangement position of the head unit 24, and heats the recording medium P conveyed by the conveying unit 21 so that the temperature of the recording medium P falls within a predetermined temperature range. The heating unit 23 has, for example, an infrared heater or the like, and energizes the infrared heater based on a control signal supplied from the control unit 40 to cause the infrared heater to generate heat.

[0023] The head unit 24 records an image by discharging ink onto the recording medium P from nozzle openings provided on the ink discharge surface facing the conveying surface of the conveying drum 211 at an appropriate timing corresponding to the rotation of the conveying drum 211 on which the recording medium P is held.

[0024] The head unit 24 has a plurality of inkjet heads, and is arranged such that the ink (droplet) discharge surface of the inkjet head and the conveying surface are separated by a predetermined distance.

[0025] In the recording apparatus 1 of the present embodiment, four head units 24 corresponding to the four colors of Y, M, C, and K are arranged at predetermined intervals in the order of the colors of Y, M, C, and K from the upstream side in the conveyance direction of the recording medium P. That is, each head unit 24 is configured to be able to eject a plurality of different types of inks.

[0026] The head unit 24 is used with its position fixed during image recording, and by sequentially ejecting ink at predetermined intervals (conveyance direction intervals) at different positions in the conveyance direction in accordance with the conveyance of the recording medium P, an image is recorded in a single-pass method.

[0027] FIG. 2 is a schematic diagram showing the configuration of the head unit 24. Here, the surface of the head unit 24 facing the outer peripheral surface of the conveyance drum 211 is shown.

[0028] Here, the head unit 24 includes three inkjet heads (recording heads) 240 attached to the attachment member 244. Each inkjet head 240 is provided with a plurality of image forming elements (recording elements) each having a pressure chamber (not shown) for storing ink, a piezoelectric element (not shown) provided on the wall surface of the pressure chamber, and a nozzle 243.

[0029] When a drive signal for deforming the piezoelectric element is input to the inkjet head 240 of this image forming element, the pressure chamber deforms due to the deformation of the piezoelectric element, the pressure in the pressure chamber changes, and ink is ejected from the nozzle 243 communicating with the pressure chamber.

[0030] The three inkjet heads 240 are arranged in a staggered grid pattern such that the arrangement ranges in the X direction of the nozzle rows are continuously connected without gaps. The arrangement range in the X direction of the nozzles 243 included in the head unit 24 covers the width in the X direction of the area on the recording medium P conveyed by the conveyance drum 211 where an image is formed. The head unit 24 is used while being fixed with respect to the rotation axis of the conveyance drum 211 during image formation. That is, the head unit 24 has a line head capable of discharging ink over the image formation possible width in the X direction with respect to the recording medium P.

[0031] The inkjet head 240 includes an ink heating unit (not shown) that heats the ink stored in the inkjet head 240, and discharges the heated ink in a sol state. When this sol-state ink is discharged onto the recording medium P, after the ink droplets land on the recording medium P, the ink is quickly gelled and solidified on the recording medium P by natural cooling.

[0032] The irradiation unit (fixing unit) 25 is arranged across the width of the conveyance unit 21, and irradiates the recording medium P placed on the conveyance unit 21 with energy rays (electromagnetic waves) such as ultraviolet rays. The irradiation unit 25 cures the ink and fixes it to the recording medium P by applying predetermined energy to the ink discharged onto the recording medium P. The irradiation unit 25 is arranged to face the conveyance surface between the arrangement position of the head unit 24 and the arrangement position of the delivery drum 271 of the delivery unit 27 in the conveyance direction.

[0033] The delivery unit 27 includes a belt loop 272 having an annular belt supported by two rollers on the inside, and a cylindrical delivery drum 271 that delivers the recording medium P from the conveyance unit 21 to the belt loop 272. The delivery unit 27 conveys the recording medium P delivered from the conveyance unit 21 onto the belt loop 272 by the delivery drum 271 and sends it out to the paper discharge unit 30 by the belt loop 272.

[0034] The paper discharge unit 30 has a plate-shaped paper discharge tray 31 on which the recording medium P sent out from the image forming unit 20 by the delivery unit 27 is placed.

[0035] Figure 3 is a block diagram showing the main functional configuration of the recording apparatus 1. The recording apparatus 1 includes a control unit 40, a head unit driving unit 50, a conveyance driving unit 60, an image processing unit 70, an input / output interface 80, and an ink supply unit 90.

[0036] The control unit 40 has a CPU 41 (Central Processing Unit), a RAM 42 (Random Access Memory), a ROM 43 (Read Only Memory), and a storage unit 44. The control unit 40 comprehensively controls the overall operation of the recording apparatus 1.

[0037] The head unit driving unit 50 supplies a driving signal corresponding to the image data to the recording elements of the head unit 24 at an appropriate timing based on the control of the control unit 40, and discharges an amount of ink corresponding to the pixel values of the image data from the nozzles of the head unit 24.

[0038] The conveyance driving unit 60 supplies a driving signal to the conveyance drum motor provided on the conveyance drum 211 based on the control signal supplied from the control unit 40 to rotate the conveyance drum 211 at a predetermined speed and timing. Also, the conveyance driving unit 60 supplies a driving signal to the motors for operating the medium supply unit 12, the delivery unit 22, and the delivery unit 27 based on the control signal supplied from the control unit 40. The conveyance driving unit 60 causes the motor to supply the recording medium P to the conveyance unit 21 and discharge it from the conveyance unit 21.

[0039] The image processing unit 70 performs predetermined image processing on the image data input from the input / output interface 80 and stores the obtained image data in the storage unit 44. This image processing includes correction processing for correcting the image data, as well as color conversion processing, gradation correction processing, pseudo halftone processing, and the like.

[0040] The input / output interface 80 is connected to the input / output interface of an external device (e.g., a personal computer) and mediates the transmission and reception of data between the control unit 40 and the external device. The input / output interface 80 is composed of, for example, any one of various serial interfaces, various parallel interfaces, or a combination thereof.

[0041] The ink supply unit 90 supplies the ink stored in the main tank 112 (see FIG. 4) to each of a plurality of inkjet heads 240 provided in the head unit 24. The ink supply unit 90 adjusts the amount of ink supplied to each of the plurality of inkjet heads 240 according to a control signal from the control unit 40.

[0042] [Configuration of Ink Supply Unit 90] Hereinafter, the configuration of the ink supply unit 90 according to the present embodiment will be described. The ink supply unit 90 includes an ink circulation system 100 having an ink flow path 110 and a determination unit (control unit) 150.

[0043] The ink supply unit 90 supplies ink from the main tank 112 to the inkjet heads 240 in the ink circulation system 100.

[0044] This ink circulation system 100 pumps ink through the ink flow path 110, the first storage tank 120, and the second storage tank 140, discharges it from the inkjet heads 240, and executes printing.

[0045] The ink circulation system 100 is a system that supplies ink from an ink tank to an inkjet head 240 as a supply target through a flow path. In this system, the ink was pumped through the flow path and the pressure was detected. Then, the inventor found that when clogging occurs in the flow path, the hydraulic pressure of the ink increases. In addition, the inventor found that when a leak occurs in the flow path, the hydraulic pressure of the ink decreases. Specifically, the inventor found that when clogging occurs in the ink flow path 110, the first storage tank 120, and the second storage tank 140, respectively, the pressure value of the ink inside each becomes higher than the normal state. Also, the inventor found that when a leak occurs in each of the ink flow path 110, the first storage tank 120, and the second storage tank 140, the pressure value of the ink inside each becomes lower than the normal state. And, in the abnormal states of "clogging" and "leak", by pumping the ink at a flow rate different from the flow rate of the ink pumped during printing (normal time), it was found that the pressure value (abnormal value) in the abnormal state and the pressure value in the normal normal state can be more clearly distinguished. Note that "clogging" is mainly the "clogging" in the ink flow path 110, but it is the "clogging" of the part as the flow path through which the ink flows, and in FIG. 4, it also includes the "clogging" at the filter 134.

[0046] Based on this, the ink supply unit 90 determines, by the determination unit 150, an abnormality (abnormality due to leak or clogging, etc.) of the ink flowing through the ink flow path 110 of the ink circulation system 100.

[0047] FIG. 4 is a diagram showing a main configuration of an ink circulation system of an inkjet recording apparatus according to an embodiment of the present invention. Note that the ink circulation system 100 shown in FIG. 4 is provided for each color of ink.

[0048] The ink circulation system 100 has an ink flow path 110 that supplies ink from the main tank 112 to the inkjet head 240. The ink circulation system 100 includes, from the upstream side of the ink flow path 110, the main tank 112, the first storage tank 120, the filter 134, the second storage tank 140, and the inkjet head 240. Further, the ink circulation system 100 has a first pressure sensor 122 and a first valve 124 connected to the first storage tank 120, and a second pressure sensor 142 and a second valve 144 connected to the second storage tank 140. In addition, the ink circulation system 100 has a supply pump (liquid feeding unit) 114, a supply valve 116, a circulation pump (liquid feeding unit) 132, a third pressure sensor 136, a first circulation valve 137, and a second circulation valve 138 on the ink flow path 110.

[0049] The ink flow path 110 has a first supply flow path 110a, an inter-tank flow path 110b, a second supply flow path 110c, and a recovery flow path 110d. The first supply flow path 110a connects the main tank 112 and the first storage tank 120. In the first supply flow path 110a, a supply pump 114 and a supply valve 116 are arranged in order from the upstream side between the main tank 112 and the first storage tank 120. The first supply flow path 110a supplies ink from the main tank 112 to the first storage tank 120.

[0050] The inter-tank flow path 110b connects the first storage tank 120 and the second storage tank 140. In the inter-tank flow path 110b, a circulation pump (liquid feeding unit) 132, a third pressure sensor 136, and a first circulation valve 137 are arranged in order from the upstream side between the first storage tank 120 and the second storage tank 140. The inter-tank flow path 110b supplies ink from the first storage tank 120 to the second storage tank 140.

[0051] The second supply flow path 110c connects the second storage tank 140 and the inkjet head 240, and supplies ink from the second storage tank 140 to the inkjet head 240.

[0052] The recovery channel 110d connects the inkjet head 240 and the first storage tank 120, and via the second circulation valve 138, recovers the ink that has not been ejected by the inkjet head 240 and returns it to the first storage tank 120.

[0053] This ink circulation system 100 supplies ink to the pressure chambers of the respective recording elements (image forming elements) in the inkjet head 240 via the second supply channel 110c. Of the ink supplied to the pressure chambers of the respective recording elements in the inkjet head 240, the ink that is not ejected from the nozzles 243 of the inkjet head 240 is recovered to the first storage tank 120 via the recovery channel 110d. Note that the second supply channel 110c is connected to the ink inlet of the inkjet head 240, and the recovery channel 110d is connected to the ink outlet of the inkjet head 240.

[0054] The inter-tank channel 110b, the second supply channel 110c, and the recovery channel 110d, together with the first storage tank 120 and the second storage tank 140, constitute a circulation channel for circulating the ink to the inkjet head 240. Note that the first supply channel 110a, the inter-tank channel 110b, the second supply channel 110c, and the recovery channel 110d are constituted by piping formed of, for example, hoses or pipes.

[0055] Also, in FIG. 2, three inkjet heads 240 are shown, but in this embodiment, the three inkjet heads 240 each have a similar configuration. When not distinguishing the three inkjet heads 240, only one of these inkjet heads 240 will be described.

[0056] The main tank 112 stores or reserves the ink supplied to the inkjet head 240 on the most upstream side of the ink flow path.

[0057] The supply pump 114 sends the ink inside the main tank 112 to the side of the inkjet head 240, specifically, to the first storage tank 120. The supply pump 114 is disposed on the first supply flow path 110a together with the supply valve 116. The ink sent out from the supply pump 114 is supplied to or stopped from being supplied to the first storage tank 120 by opening and closing the supply valve 116.

[0058] The supply pump 114 is disposed, for example, between the main tank 112 and the first storage tank 120, that is, in the first supply flow path 110a. When the supply valve 116 is open, the supply pump 114 sends the ink in the first supply flow path 110a to the first storage tank 120. The supply pump 114 is controlled by a control signal from the control unit 40 or the ink supply unit 90.

[0059] The supply valve 116 is a valve that opens and closes the ink flow path from the main tank 112 to the first storage tank 120 and is normally in a closed state (NC), and is opened during supply. The supply valve 116 controls the supply state or the stop of the supply of ink from the main tank 112 to the first storage tank 120.

[0060] The first storage tank 120 stores the ink supplied from the main tank 112 during image formation and supplies the stored ink to the second storage tank 140 provided on the downstream side via the tank - to - tank flow path 110b.

[0061] The first valve 124 opens and closes the first storage tank 120 to seal or open the inside of the first storage tank 120. The first valve 124 is controlled by the control unit 40 or the ink supply unit 90 (determination unit 150) and is normally in an open state.

[0062] The first pressure sensor 122 detects the ink pressure in the ink flow path 110 (for example, the ink pressure in the first storage tank 120 via the air in the first storage tank 120). The first pressure sensor 122 outputs a sensor signal indicating the magnitude of the detected pressure (hereinafter, the pressure sensor value) [N / m 2 . The sensor signal of the first pressure sensor 122 is sent to the determination unit 150. Note that the first pressure sensor 122 is connected to, for example, the first storage tank 120.

[0063] The circulation pump 132 sends the ink inside the first storage tank 120 to the inkjet head 240 side, specifically to the second storage tank 140, via the ink flow path 110, for example, the inter-tank flow path 110b.

[0064] The circulation pump 132 sends the ink in the ink flow path 110 (for example, the inter-tank flow path 110b) to the second storage tank 140 via the filter 134, and further supplies it to the inkjet head 240 via the second storage tank 140.

[0065] The circulation pump 132 sends the ink in the circulation flow path to the inkjet head 240 so as to circulate the ink. The circulation pump 132 closes the supply valve 116, the first valve 124, and the second valve 144, and opens the first circulation valve 137 and the second circulation valve 138 to put the circulation flow path in a communicating state, and sends the ink to the downstream side. As a result, an ink circulation flow is generated in the circulation flow path by the circulation pump.

[0066] The circulation pump 132 supplies ink to the inkjet head 240 and returns the ink not ejected from the inkjet head 240 to the first storage tank 120 via the recovery flow path 110d. That is, by driving the circulation pump 132, an ink circulation flow that returns from the first storage tank 120 to the second storage tank 140, passes through the inkjet head 240, and returns to the first storage tank 120 is generated in the circulation path. The circulation pump 132 is controlled by a control signal from the control unit 40 or the ink supply unit 90.

[0067] Filter 134 removes foreign substances such as dust and dirt mixed in the ink flowing through the ink flow path 110. In FIG. 4, the filter 134 is disposed between the first storage tank 120 and the second storage tank 140, that is, in the ink intermediate flow path 110b. The filter 134 is configured to include, for example, a nonwoven fabric having a porous structure.

[0068] The second storage tank 140 has an inlet (ink inlet) communicating with the first storage tank 120 via the tank intermediate flow path 110b and an outlet (ink outlet) communicating with the ink inlet of the corresponding ink jet head 240 via the second supply flow path 110c. Note that a plurality of second storage tanks 140 are provided corresponding to the plurality of ink jet heads 240.

[0069] The second storage tank 140 temporarily stores the ink supplied from the first storage tank 120 during image formation and supplies the ink to the ink jet head 240 through the second supply flow path 110c.

[0070] The second pressure sensor 142 detects the ink pressure in the ink flow path 110 (for example, the ink pressure in the second storage tank 140 via the air in the second storage tank 140). The second pressure sensor 142 outputs a sensor signal indicating the magnitude of the detected pressure (hereinafter, pressure sensor value) [N / m 2 .

[0071] The sensor signal of the second pressure sensor 142 is sent to the determination unit 150 (which may be the control unit 40). Note that the second pressure sensor 142 is connected to the second storage tank 140, for example.

[0072] The second valve 144 opens and closes the second storage tank 140 to seal or open the inside of the second storage tank 140. The second valve 144 is controlled by the control unit 40 or the ink supply unit 90 (determination unit 150) and is normally open.

[0073] For simplicity, only one inkjet head 240 is shown in FIG. 4, but actually, more inkjet heads 240 can be added. In this case, the second storage tank 140, the inter-tank flow path 110b, and the second supply flow path 110c may be added by the number of the added inkjet heads 240.

[0074] The inkjet head 240 has an inlet (ink inlet) communicating with the second storage tank 140 via the second supply flow path 110c, and an outlet (ink outlet) communicating with the first storage tank 120 via the recovery flow path 110d.

[0075] In this example, the ink supplied to the inkjet head 240 through the second supply flow path 110c and the remaining ink not ejected by the inkjet head 240 are recovered into the first storage tank 120 through the recovery flow path 110d by the operation of the circulation pump 132. The recovered ink is reused by being supplied again from the first storage tank 120 to the inkjet head 240 through the pipe t4 or the like.

[0076] The first circulation valve 137 and the second circulation valve 138 open and close to recover and circulate the ink supplied to the inkjet head 240 but not ejected by the inkjet head 240 for reuse. The first circulation valve 137 and the second circulation valve 138 are controlled by the control unit 40 or the ink supply unit 90 (determination unit 150) and are normally in a closed state (NC).

[0077] Note that the ink circulation system 100 has a third pressure sensor 136 directly disposed on the ink flow path 110. The third pressure sensor 136 is installed, for example, on the inter-tank flow path 110b between the circulation pump 132 and the filter 134. The third pressure sensor 136 detects the pressure of the ink in the inter-tank flow path 110b and outputs a sensor signal indicating the magnitude of the detected pressure (hereinafter, the pressure sensor value) [N / m 2 .

[0078] The determination unit 150 is connected to the control unit 40 and, like the control unit 40, has a CPU, a RAM, a ROM, and a storage unit. The determination unit 150 is mainly connected to each part of the ink circulation system 100 (each valve 116, 124, 137, 138, 142, the first to third pressure sensors 122, 142, 136) and also has the function of appropriately controlling these. Note that the determination unit 150 may be configured as a component included in the control unit 40.

[0079] The determination unit 150 mainly drives a liquid feed pump (specifically, the circulation pump 132) to feed ink into the ink flow path 110, and detects the pressure value of the ink by each of the first pressure sensor 122, the second pressure sensor 14, and the third pressure sensor 136.

[0080] The determination unit 150 feeds ink to the ink flow path 110, the first storage tank 120, and the second storage tank 140 at a flow rate different from the normal time, and compares the detected pressure value with the pressure value detected when flowing at the normal time flow rate.

[0081] Through this comparison, the determination unit 150 detects an abnormality, particularly a serious abnormality (failure), in the ink flow path 110, the first storage tank 120, the second storage tank 140, etc. before it occurs.

[0082] The determination unit 150 controls each part constituting the ink circulation system 100 based on information such as information regarding the execution and non - execution of printing, for example, to execute and not execute printing. The determination unit 150 sets a target value for the back pressure of the nozzles 243 of the inkjet head 240. The determination unit 150 performs feedback control on the output of the supply pump 114 so that the ink pressure in the first storage tank 120 and the second storage tank 140 reaches the set target values (the first and second target pressures).

[0083] [Abnormality Detection Control of Ink Flow Path in Ink Circulation System 100] In the ink circulation system 100, the determination unit 150 detects the hydraulic pressure of the ink in the ink flow path 110 through which ink is fed at a flow rate different from that during printing. Based on this detection result, the determination unit 150 will explain the process of detecting an abnormality in the ink flow path 110, particularly an abnormality before it becomes a serious abnormality (failure). Also, since the abnormality detection control of the flow path cannot be performed during printing, it is performed at a timing different from the printing mode. Further, by accumulating the ink pressure (hydraulic pressure) value in the ink flow path during normal operation as data, more sensitive control can be performed. Therefore, for example, it is preferable to perform the abnormality detection control of the flow path when the power of the inkjet recording apparatus 1 is turned on. As a result, by accumulating the detection data, it becomes possible to predict an abnormality that will occur after a predetermined period due to an abnormality that occurs over time.

[0084] [When using the first pressure sensor] With reference to FIGS. 5 and 6, the ink circulation system 100 (determination unit 150) will explain the flow path abnormality detection process using the first pressure sensor 122. Here, an example is shown in which the determination unit 150 detects the hydraulic pressure of the ink fed at a flow rate lower than that during normal printing and determines an abnormality in the ink flow path 110 by comparing it with the normal pressure value.

[0085] FIG. 5 is a flowchart showing an example of the in-flow path abnormality detection process using the first pressure sensor. As shown in FIG. 5, for example, when a signal indicating the start of the ink flow path abnormality detection process is input from the control unit 40 to the ink supply unit 90, the determination unit 150 executes the flow path failure detection process.

[0086] In step S1 in the ink circulation system 100, the determination unit 150 closes the first valve 124 and proceeds to step S2. In step S2, the determination unit 150 opens the first circulation valve 137 and proceeds to step S3.

[0087] In step S3, the determination unit 150 drives (turns "ON") the circulation pump 132 to feed the ink so that ink at a flow rate different from normal, for example, a flow rate less than the normal flow rate, flows in the ink flow path.

[0088] The determination unit 150 drives the circulation pump 132 so that ink is supplied to the first storage tank 120 at a flow rate less than the normal flow rate, for example, at half of the normal flow rate.

[0089] In step S4, the determination unit 150 measures the pressure applied to the ink by the first pressure sensor 122 and proceeds to step S5. In step S5, the determination unit 150 performs a fault diagnosis based on the measured pressure value (for example, the diagram shown in FIG. 6A).

[0090] The fault diagnosis is determined by comparing the pressure value measured by the determination unit 150 with the normal value of the hydraulic pressure of the ink when a liquid is sent at a flow rate different from the normal flow rate set in advance from a storage unit (which may be the storage unit 44) not shown in the figure. In step S5, the determination unit 150 compares the actually measured pressure value with the preset normal value. If the measured value is different from the normal value, it is determined that there is a leak (fault). In the determination of step S5, if the measured value is the normal value or a value regarded as the normal value, the determination unit 150 determines that the ink flow path is normal.

[0091] The normal value or the value regarded as the normal value is caused by variations that occur even when there is no abnormality in general pressure measurement. This variation is, for example, the variation due to individual differences in the pump (circulation pump) itself. Therefore, the circulation pump 132 is a pump with a clear performance in advance. When replacing parts such as the pump, data on the pressure transition for each pump to be used is acquired and stored. By comparing with this value, an abnormality in the ink flow path is detected. Specifically, the normal value for each pump operating normally is set within a predetermined range. By comparing the value within this range with the actually measured value, it is possible to detect the variation of the values in the abnormal state itself and eliminate the variation due to individual differences in the pump.

[0092] In this way, after the valve operation, the circulation pump 132 is rotated to measure the pressure value in the ink flow path. For example, even if the normal flow rate is set to 3 - 6 cc / sec, variations occur due to individual differences in the pumps and usage conditions as described above. For example, if there is an abnormality (leak) in the flow path around the first storage tank 120 at a flow rate of 5 cc / sec during normal measurement, the negative pressure value measured by the first pressure sensor 122 becomes smaller, and in FIG. 6B, it shows a pressure decrease of about 6% measured at the normal flow rate.

[0093] On the other hand, when the pressure measurement is carried out with the flow rate of the circulation pump 132 being reduced to half of the normal value, for example, 1.5 - 3 cc / sec (2.5 cc / sec during this measurement), the pressure decrease during an abnormality (leak) is about 24%, showing a large difference from the normal time.

[0094] As described above, variations in the normal pressure values occur not only due to individual differences in the pumps but also, for example, due to variations in the amount of air in the first storage tank 120, the amount of air in the ink, the ink temperature, the power supply situation, etc., resulting in certain variations. Therefore, when measuring the hydraulic pressure of the ink while changing the various variation factors described above, it was found that variations of -4.2 to -4.8 kPa occur at the normal flow rate. If there are variations within such a range in the normal value, there are cases where the pressure during an abnormality (leak) overlaps with the normal pressure, making it difficult to judge a failure. However, when the hydraulic pressure was measured by sending ink with a flow rate less than normal into the ink flow path 110, particularly when the ink flow rate was half of the normal ink flow rate, the variation in the normal ink was -3.5 to -4.1 kPa. As a result, the pressure of the ink during an abnormality (leak) does not overlap with the pressure of the ink during normal times, enabling failure judgment.

[0095] FIG. 6A is a diagram showing the relationship between the normal pressure value and the abnormal pressure value of the hydraulic pressure of ink supplied at a flow rate less than normal in the ink flow path. FIG. 6B is a diagram showing the relationship between the normal pressure value and the abnormal pressure value of the hydraulic pressure of ink supplied at the normal flow rate in the ink flow path.

[0096] Specifically, as shown in FIGS. 6A and 6B, when the liquid is fed at a flow rate that is half of the normal ink flow rate (a flow rate lower than normal), the difference between the normal and abnormal pressure values of the ink is greater than when the liquid is fed at the normal ink flow rate.

[0097] In FIG. 6A, at half of the normal ink flow rate, the pressure value indicating the normal value and the pressure value indicating an abnormality (leak) have a difference of 24%, and the difference between the two in FIG. 6B is 6%. The difference between the pressure values at normal and abnormal (leak) times shown in FIG. 6A is greater than the difference between the two in FIG. 6B.

[0098] That is, when the ink flow rate in the ink flow path is reduced to half of the normal value, the determination unit 150 can more easily compare the pressure value of the hydraulic pressure of the ink in the first storage tank 120 (which may also be the ink flow path) with the normal value and more clearly determine an abnormality.

[0099] Note that although the flow rate is set to half of the normal value as a flow rate lower than that during normal printing, it is not limited to this. As long as the flow rate is lower than that during normal printing and is 0.1 times or more and 0.7 times or less of the flow rate during normal printing, within this range of flow rates, as described above, even if there is variation in the detected value, the pressure value in the normal state and the pressure value in the abnormal state do not overlap, and the two can be distinguished.

[0100] In this way, when the detected hydraulic pressure of the ink is lower than the normal pressure value, it is determined that there is a failure due to a leak in the ink tank (similarly for the ink flow path), but it can also be determined that it is a failure of the on-off valve disposed in the ink flow path. It may also be determined that it is a failure of the circulation pump 132.

[0101] In this case, similarly using the third pressure sensor, the hydraulic pressure of the ink fed at a flow rate different from that during normal printing is detected and compared with the normal pressure value. Thereby, an abnormality in a minor state before it becomes a serious abnormality (failure) can be detected.

[0102] [When using the second pressure sensor] Using FIGS. 7 and 8, the ink circulation system 100 (determination unit 150) will explain the abnormal detection process of the flow path using the second pressure sensor 142. FIG. 7 is a flowchart showing an example of the abnormal detection process in the flow path using the second pressure sensor.

[0103] As shown in FIG. 7, for example, when a signal indicating the start of the detection process of the abnormality of the ink flow path is input from the control unit 40 to the ink supply unit 90, the determination unit 150 executes the flow path failure detection process.

[0104] In step S21 of the ink circulation system 100, the determination unit 150 closes the second valve 144 and proceeds to step S22. In step S22, the determination unit 150 opens the second circulation valve 138 and proceeds to step S23.

[0105] In step S23, the determination unit 150 drives (turns "ON") the circulation pump 132 so that ink with a flow rate different from normal, for example, a flow rate larger than the normal ink flow rate, flows in the ink flow path, and sends the ink.

[0106] The determination unit 150 drives the circulation pump 132 so that ink is supplied to the second storage tank 140 at a flow rate higher than the normal flow rate, for example, at twice the normal flow rate.

[0107] In step S24, the determination unit 150 measures the pressure applied to the ink by the second pressure sensor 142 and proceeds to step S25. In step S25, the determination unit 150 performs a failure diagnosis based on the measured pressure value (refer to the normal value and abnormal value shown in FIG. 8).

[0108] The failure diagnosis is determined by comparing the pressure value measured by the determination unit 150 with the normal value of the liquid pressure of the ink when sending liquid at a flow rate different from normal set in advance from a storage unit (storage unit 44) not shown.

[0109] In step S25, the determination unit 150 compares the actually measured pressure value with a preset normal value. If the measured value is different from the normal value, it determines that there is an abnormality (clogging, failure). In the determination of step S25, if the measured value is the normal value or a value regarded as the normal value, the determination unit 150 determines that the ink flow path is normal.

[0110] In this way, after the valve operation, the circulation pump is rotated to measure the pressure value.

[0111] If the filter 134 is clogged, the first circulation valve 137 fails, or the ink flow path (second supply flow path 110c) between the second storage tank 140 and the ink jet head 240 is clogged, the pressure value of the second pressure sensor 142 will decrease. Therefore, similar to the first pressure sensor 122, the flow rate of the circulation pump 132 is set to measure the pressure value.

[0112] In order to detect an abnormality (clogging) in the ink flow path, the flow rate was increased, for example, in this case, the liquid was sent at twice the normal flow rate, and the pressure was measured. The pressure reduction rate during the occurrence of an abnormality (clogging) was 11% in the case of the normal flow velocity, while a large difference of 22% could be obtained at twice the flow rate.

[0113] FIG. 8A is a diagram showing the relationship between the normal pressure value and the abnormal pressure value of the liquid pressure of the ink supplied at a flow rate higher than normal in the ink flow path. FIG. 8B is a diagram showing the relationship between the normal pressure value and the abnormal pressure value of the liquid pressure of the ink supplied at the normal flow rate in the ink flow path.

[0114] Specifically, as shown in FIGS. 8A and 8B, it was found that the difference between the normal and abnormal values of the pressure value of the ink is larger when the liquid is sent at twice the normal flow rate (a flow rate higher than normal) than when the liquid is sent at the normal ink flow rate.

[0115] In FIG. 8A, the difference between the pressure value indicating the normal value and the pressure value indicating an abnormality (clogging) is 22%, and the difference between the two in FIG. 8B is 11%. The difference between the pressure values in the normal and abnormal (clogging) states shown in FIG. 8A is larger than the difference between the two in FIG. 8B. When the ink flow rate in the ink flow path is reduced to half of the normal value, the determination unit 150 can more easily compare the pressure value of the hydraulic pressure of the ink in the second storage tank 140 (which may be an ink flow path) with the normal value and more clearly determine an abnormality.

[0116] Therefore, the determination unit 150 can clearly determine a normal state and a failure (abnormality, clogging) state that cannot be discriminated at the normal ink flow rate, and then can prevent a serious failure by corresponding to a serious failure among minor failures.

[0117] Note that the flow rate is set to twice the normal flow rate as a flow rate higher than that during normal printing, but it is not limited to this. As long as the flow rate is higher than that during normal printing and is 1.5 times or more and 3 times or less the flow rate during normal printing, within this range of flow rates, as described above, even if there is variation in the detected value, the pressure value in the normal state and the pressure value in the abnormal state do not overlap, and the two can be distinguished.

[0118] In this way, when the detected hydraulic pressure of the ink is higher than the normal pressure value, it is determined as a failure due to a leak in the ink tank (similarly for the ink flow path), but it can also be determined as a failure of the on-off valve disposed in the ink flow path. It may also be determined as a failure of the circulation pump 132.

[0119] In this case, similarly using the third pressure sensor, the hydraulic pressure of the ink fed at a flow rate different from that during normal printing is detected and compared with the normal pressure value. Thereby, an abnormality in a minor state before becoming a serious abnormality (failure) can be detected.

[0120] [When Using the Third Pressure Sensor] The determination unit 150 uses the third pressure sensor 136 to feed the ink at a flow rate different from that during printing and measures the hydraulic pressure of the ink in the ink flow path (the inter-tank flow path 110b).

[0121] For example, as in the case of using the first pressure sensor 122, ink with a flow rate less than the normal flow rate is fed. Also, for example, as in the case of using the second pressure sensor 142, ink with a flow rate greater than the normal flow rate is fed. Then, the determination unit 150 detects the hydraulic pressure of the fed ink and compares it with the normal hydraulic pressure to determine whether there is an abnormality in the ink flow path respectively. In this way, even when using the third pressure sensor 136, it is possible to determine a failure (abnormality before a serious abnormality) in the flow path 110b between the tanks in the same manner as when using the first pressure sensor 122 and the second pressure sensor 142.

[0122] The first pressure sensor 122 and the second pressure sensor 142 measure the air pressure in the first storage tank 120 and the second storage tank 140, and use it as a medium to measure the hydraulic pressure of the ink inside each tank. Since air has the effect of absorbing pressure, when using air as the medium, the sensitivity of the sensor will decrease slightly. In contrast, since the third pressure sensor 136 is directly arranged in the ink flow path 110, the sensitivity of the first pressure sensor and the second pressure sensor will not decrease.

[0123] <Effect> When detecting an abnormality (failure) in the ink flow path, in the conventional device, since the configuration is to detect an error in the normal use state at the normal flow rate using a pressure sensor, it is impossible to detect until a serious failure (abnormality) actually occurs in the ink flow path, and it is impossible to present that fact. Also, since it is impossible to determine whether the failure is a clogging-type failure or a leakage-type failure, even when detecting a serious failure that has occurred and repairing it, the failure location is unknown and it takes time for repair.

[0124] In contrast, according to the inkjet recording apparatus of the present embodiment, the ink is fed at a flow rate different from the normal flow rate, and the pressure (corresponding to the hydraulic pressure) in the ink flow path (the ink flow path 110 itself, the first storage tank 120, the second storage tank 140) at that time is detected.

[0125] It has been found that there are the following two cases for detecting an abnormality in the ink flow path. One is the case where when the ink feeding amount is larger than the normal total amount, the pressure fluctuation of the fed ink becomes larger and the detection accuracy increases. For example, abnormal systems where a larger feeding amount is advantageous include clogging of the ink flow path or clogging of the filter 134. In the case of clogging system abnormalities (failures), since the ink with a higher flow rate accumulates at the clogging part in the ink flow path, the pressure becomes significantly higher.

[0126] The other is the case where when the ink feeding amount is smaller than the normal feeding amount, the pressure fluctuation of the ink becomes larger and the detection accuracy increases. For example, abnormal systems where a smaller feeding amount is advantageous include leakage of the ink flow path or performance degradation of the circulation pump (pump) 132. In the case of abnormalities (failures) such as leakage systems or pump performance degradation, the ink flow rate decreases compared to normal. When the original ink flow rate is sufficiently high, even if the ink flow rate decreases, the decrease amount is likely to be buried in the error within the normal variation range, resulting in poor detection sensitivity. Conversely, when the ink flow rate is lowered, the sensitivity increases.

[0127] The inkjet recording apparatus 1 controls the detection of abnormalities in the ink flow path using the determination unit 150, changes the ink feeding amount, and detects the pressure (hydraulic pressure) of the ink.

[0128] That is, it detects abnormalities in the ink flow path that supplies ink from the ink tank 112 to the inkjet head (recording head) 240. The ink in the ink flow path 110 is fed at a flow rate different from that during printing, and then the hydraulic pressure of the ink fed at a flow rate different from that during printing is detected in the ink flow path 110. Next, the detected hydraulic pressure of the ink is compared with the hydraulic pressure of the ink normally fed at a flow rate different from that during printing to determine whether there is an abnormality in the ink flow path 110.

[0129] As a result, the inkjet recording apparatus 1 can detect the variation itself of the values in the abnormal state by using the determination unit 150, and can detect an abnormality in the ink flow path, particularly a failure that leads to a serious failure, with high detection accuracy for each abnormal system. Specifically, even a minor abnormality can be detected, so that repairs can be easily performed. Furthermore, when it deteriorates (gets clogged) according to the usage time like the filter 134, it can also be used for predictive detection of durability.

[0130] The embodiments of the present invention have been described above. Note that the above description is an illustration of a preferred embodiment of the present invention, and the scope of the present invention is not limited thereto. That is, the description of the configuration of the above device and the shape of each part is an example, and it is obvious that various changes and additions to these examples are possible within the scope of the present invention.

Industrial Applicability

[0131] The inkjet recording apparatus according to the present invention is useful as having an effect of being able to detect a failure particularly before it becomes a serious failure and enabling easy repair.

Explanation of Signs

[0132] 1 Inkjet recording apparatus 10 Paper feeding unit 11 Paper feed tray 12 Medium supply unit 20 Image forming unit 21 Conveying unit 22 Delivery unit 23 Heating unit 24 Head unit 25 Irradiation unit 27 Delivery section 30 Paper discharge unit 31 Paper discharge tray 40 Control unit 44 Storage unit 50 Head unit driving unit 60 Conveying driving unit 70 Image processing unit 80 Input / output interface 90 Ink Supply Unit 100 Ink Circulation System 110a First Supply Flow Path 110b Ink Intermediate Flow Path 110c Second Supply Flow Path 110d Recovery Flow Path 112 Main Tank 114 Supply Pump 116 Supply Valve 120 First Storage Tank 122 First Pressure Sensor 124 First Valve 132 Circulation Pump (Liquid Feeding Section) 134 Filter 136 Third Pressure Sensor 137 First Circulation Valve 138 Second Circulation Valve 140 Second Storage Tank 142 Second Pressure Sensor 144 Second Valve 150 Judgment Section 211 Conveyor Drum 221 Guide Arm Section 222, 271 Transfer Drum 240 Ink Jet Head (Recording Head) 243 Nozzle 244 Mounting Member 272 Belt Loop

Claims

1. In an inkjet recording apparatus including an ink flow path connecting a recording head and an ink tank for storing ink to be supplied to the recording head, a pressure sensor for detecting the hydraulic pressure in the ink flow path or in the ink tank; a liquid feeding unit for applying pressure to the ink in the ink flow path or in the ink tank to feed the liquid at a flow rate different from that during printing; a determination unit for determining whether there is an abnormality in the ink flow path based on the hydraulic pressure of the ink fed at the different flow rate; having an inkjet recording apparatus.

2. The flow rate different from that during printing is a flow rate higher than that during normal printing, and the determination unit detects the hydraulic pressure of the ink at the flow rate of the ink fed at the high flow rate and determines the abnormality by comparing it with the normal pressure value. The inkjet recording apparatus according to Claim 1.

3. The flow rate different from that during printing is a flow rate lower than that during normal printing, and the determination unit detects the hydraulic pressure of the ink at the flow rate of the ink fed at the low flow rate and determines the abnormality by comparing it with the normal pressure value. The inkjet recording apparatus according to Claim 1.

4. When the detected hydraulic pressure of the ink is higher than the normal pressure value, the determination unit determines that the abnormality is a clogging in the ink flow path or in the ink tank. The inkjet recording apparatus according to Claim 2.

5. When the detected hydraulic pressure of the ink is lower than the normal pressure value, the determination unit determines that the abnormality is a leak in the ink flow path or in the ink tank. The inkjet recording apparatus according to Claim 3.

6. When the detected hydraulic pressure of the ink is lower than the pressure value during normal operation, the determination unit determines that the abnormality is a failure of the pump as the liquid feeding unit. The inkjet recording apparatus according to claim 3.

7. When the detected hydraulic pressure of the ink is lower than the pressure value during normal operation, the determination unit determines that the abnormality is a failure of the on-off valve disposed in the ink flow path. The inkjet recording apparatus according to claim 3.

8. The high flow rate is 1.5 times or more and 3 times or less the flow rate during normal printing. The inkjet recording apparatus according to claim 2.

9. The low flow rate is 0.1 times or more and 0.7 times or less the flow rate during normal printing. The inkjet recording apparatus according to claim 3.

10. An ink flow path abnormality detection method for supplying ink from an ink tank to a recording head, A liquid feeding step of feeding the ink in the ink flow path at a flow rate different from that during printing, A detection step of detecting the hydraulic pressure of the ink fed at a flow rate different from that during printing in the ink flow path, A determination step of comparing the detected hydraulic pressure with the hydraulic pressure of the ink normally fed at a flow rate different from that during printing to determine whether there is an abnormality in the ink flow path, having An ink flow path abnormality detection method.

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