JP2017113976A - Inkjet printer and liquid feeding state confirming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet printer that can confirm whether or not ink is normally circulating without installing a sensor in a circulation pathway for the ink.SOLUTION: The inkjet printer comprises: a head 32 comprising a plurality of nozzles 33 for discharging ink to a recording medium; a tank 53 for supplying ink to the head 32; ink circulation means 500 for feeding ink from the head 32 to the tank 53; and a pressure adjusting portion 60 that when pressure in the tank 53 is a predetermined value or less, performs negative pressure reducing processing by which pressure in the tank 53 is raised. Further, the printer comprises: an operation detecting portion that detects the number of times or frequencies of the negative pressure reducing processing performed by the pressure adjusting portion 60; and an error detecting portion that determines whether or not the ink circulation portion 500 is normally operated, on the basis of a detection signal from the operation detecting portion.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an ink jet printer and a liquid feeding state confirmation method in an ink jet printer.

  Conventionally, a printing apparatus having an ejection head that ejects ink onto a recording medium has been used. A conventional printing apparatus is described in Patent Document 1, for example.

  When ink is not ejected from the ejection head for a long time, the ink component may settle or aggregate in the ejection head or in the conduit through which the ink passes. When the ink component settles or aggregates, there is a risk that ink ejection from the ejection head may be defective. Therefore, in this type of printing apparatus, it is desirable to circulate ink during a period when the printing process is not performed to prevent sedimentation and aggregation of ink components.

JP 2001-138544 A

  In the ink circulation process, if the ink components have already settled or aggregated inside the ejection head or the pipe line through which the ink passes, the ink may not be normally circulated. For this reason, in the ink circulation process, it is necessary to confirm whether the ink is normally circulated.

  In the printing apparatus described in Patent Document 1, a pressure sensor is provided in an ink circulation path, and whether or not ink is normally circulated is confirmed with reference to a measurement value of the pressure sensor. However, when the pressure sensor is provided, the number of components of the circulation path increases, and the manufacturing cost of the printing apparatus increases. In addition, when ink components settle or aggregate around the pressure sensor, it is difficult for the pressure sensor to accurately measure the pressure.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a technique capable of confirming whether ink is normally circulated without providing a sensor in the ink circulation path. To do.

  In order to solve the above problems, a first invention of the present application includes a head including a plurality of nozzles that eject ink to a recording medium, a tank that stores the ink and supplies the ink to the head, An ink recirculation means for sending the ink from the head to the tank; a pressure adjusting section for performing a negative pressure reduction process for increasing the pressure in the tank when the pressure in the tank becomes a predetermined value or less; Based on a detection signal from the operation detection unit that detects the number or frequency of the negative pressure reduction processing performed by the pressure adjusting unit, and a detection signal from the operation detection unit, it is determined whether or not the ink reflux unit is operating normally. And an error detection unit.

  A second invention of the present application is the ink jet printer according to the first invention, wherein the pressure adjusting unit is interposed in the atmosphere opening pipe that communicates the tank and the outside, and is inserted in the atmosphere opening pipe. And an atmosphere release valve that switches between a communication state and a shut-off state, and the pressure adjusting unit performs the negative pressure reduction process by opening the atmosphere release valve to release the tank to the atmosphere.

  A third invention of the present application is the ink jet printer according to the first invention or the second invention, wherein the error detecting unit operates normally when the number of times or the frequency does not match a predetermined condition. Judge that it is not.

  A fourth invention of the present application is the ink jet printer according to any one of the first to third inventions, wherein the ink reflux means includes an ink storage portion for storing the ink, and the ink from the head to the ink storage portion. And a supply pump for feeding the ink from the ink reservoir to the tank.

  A fifth invention of the present application is the ink jet printer according to the fourth invention, wherein the error detection unit determines whether or not the ink reflux means is operating normally based on the detection signal when the reflux pump is operated. Judging.

  A sixth invention of the present application is the ink jet printer according to any one of the first to fifth inventions, comprising a plurality of the heads.

  A seventh invention of the present application is the ink jet printer according to any one of the first to sixth inventions, wherein an error is notified when the error detecting unit determines that the ink reflux means is not operating normally. An error notification unit is further included.

  According to an eighth aspect of the present invention, there is provided a head having a plurality of nozzles for ejecting ink to a recording medium, a tank for supplying the ink to the head, and ink reflux for feeding the ink from the head to the tank. A liquid feeding state confirmation method for confirming a liquid feeding state of the ink from the head to the tank, and a) while refluxing the ink from the head to the tank, Measuring the pressure in the tank and determining whether the pressure in the tank has become a predetermined value or less; b) during the execution of the step a), the pressure in the tank is not more than the predetermined value. When a negative pressure is reached, a step of performing a negative pressure reduction process for increasing the pressure in the tank, and c) detecting and detecting the number or frequency of the negative pressure reduction process during the execution of the step a). Based on the number or the frequency to, and a step of determining whether the ink recirculation means is operating normally.

  A ninth invention of the present application is the liquid feeding state confirmation method of the eighth invention, wherein, in the step b), the negative pressure reducing process is a process of opening the tank to the atmosphere.

  The tenth invention of the present application is the liquid feeding state confirmation method of the eighth invention or the ninth invention, wherein in the step c), the number of times or the frequency of the negative pressure reduction processing does not match a predetermined condition. , It is determined that the ink reflux means is not operating normally.

  According to the first to tenth aspects of the present application, it is possible to confirm whether or not the ink is normally circulated without providing a sensor in the ink circulation system path.

1 is a diagram conceptually illustrating a configuration of a printing apparatus according to an embodiment. It is a bottom view of the head unit concerning one embodiment. It is the figure which showed notionally the structure of the ink supply system of the printing apparatus which concerns on one Embodiment. It is the block diagram which showed the control system of the printing apparatus which concerns on one Embodiment. It is a flowchart which shows the flow of the ink circulation process which concerns on one Embodiment. It is a flowchart which shows the flow of the meniscus control process which concerns on one Embodiment. It is a flowchart which shows the flow of the ink circulation process which concerns on a modification. It is a flowchart which shows the flow of the ink circulation process which concerns on a modification.

  Embodiments of the present invention will be described below with reference to the drawings. Hereinafter, the direction in which the printing paper 9 is transported is referred to as “transport direction”, and the horizontal direction orthogonal to the transport direction is referred to as “width direction”.

<1. Configuration of printing device>
FIG. 1 is a diagram conceptually showing the configuration of a printing apparatus 1 according to an embodiment of the present invention. FIG. 2 is a bottom view of the head unit 30. FIG. 3 is a diagram conceptually illustrating the configuration of the ink supply system of the printing apparatus 1.

  The printing apparatus 1 ejects ink droplets from the plurality of ejection heads 32 of the head unit 30 onto the printing paper 9 while conveying the printing paper 9 that is a long belt-like recording medium, thereby forming a color image on the printing paper 9. Is an inkjet printer. As illustrated in FIGS. 1 to 3, the printing apparatus 1 includes a transport mechanism 20, five head units 30, a UV lamp 40, an ink supply unit 50, a pressure adjustment unit 60, an operation unit 70, and a control unit 10. .

  The transport mechanism 20 is a mechanism for transporting the printing paper 9 in the transport direction, which is the longitudinal direction of the print paper 9. The transport mechanism 20 according to the present embodiment includes an unwinding unit 21, a plurality of transport rollers 22, and a winding unit 23.

  A motor (not shown) serving as a power source is connected to the unwinding unit 21, the plurality of transport rollers 22, and the winding unit 23. When the control unit 10 drives the motor, the unwinding unit 21, the plurality of transport rollers 22, and the winding unit 23 rotate. Note that a part or all of the transport roller 22 may be a driven roller that is not connected to the motor and rotates according to the movement of the printing paper 9.

  The plurality of transport rollers 22 constitute a transport path for the printing paper 9. Each conveyance roller 22 guides the printing paper 9 to the downstream side of the conveyance path by rotating about the horizontal axis. Further, when the printing paper 9 comes into contact with the plurality of conveying rollers 22, tension is applied to the printing paper 9. In this manner, the printing paper 9 is fed out from the unwinding unit 21 and conveyed to the winding unit 23 along the conveyance path constituted by the plurality of conveyance rollers 22. The conveyed printing paper 9 is collected to the winding unit 23.

  The five head units 30 are arranged above the transport path of the printing paper 9 and spaced in the transport direction. The five head units 30 discharge white (W), cyan (C), magenta (M), yellow (Y), and black (K) ink droplets onto the upper surface of the printing paper 9, respectively. In the printing apparatus 1 of the present embodiment, UV curable UV ink is used.

  The printing apparatus 1 according to the present embodiment ejects ink droplets from each head unit 30 while the printing paper 9 passes only under each head unit 30 once, thereby causing a desired image pattern on the printing paper 9. Is a so-called one-pass type recording apparatus. Since the structures of the five head units 30 are substantially the same, the structure of one head unit 30 will be described below.

  As shown in FIG. 2, the head unit 30 includes a housing 31 and a plurality of ejection heads 32 attached to the housing 31. Each discharge head 32 has a discharge surface exposed on the lower surface of the housing 31. A plurality of nozzles 33 are two-dimensionally arranged on the ejection surface, which is the lower surface of the ejection head 32. The individual nozzles 33 are arranged with their positions shifted in the width direction, and one nozzle 33 is assigned to an area of 1 pixel width on the printing paper 9.

  As shown in FIG. 2, the plurality of ejection heads 32 are arranged in a staggered manner (alternatingly in an oblique manner) along the width direction. That is, the plurality of ejection heads 32 includes a first ejection head row 301 arranged in the width direction and a second ejection head row 302 arranged in the width direction at a position downstream of the first ejection head row 301. And have. The ejection heads 32 of the first ejection head row 301 and the ejection heads 32 of the second ejection head row 302 are alternately arranged in the width direction. As described above, the plurality of ejection heads 32 are arranged in a staggered manner, so that the plurality of ejection heads 32 are arranged at a high density in the width direction.

  As shown in FIG. 3, each of the ejection heads 32 includes a casing 321, an ink storage chamber 322 and a plurality of ink chambers 323 provided in the casing 321, an ink supply port 324, an ink discharge port 325, and a plurality of And a nozzle 33.

  The ink storage chamber 322 is primarily filled with ink supplied from the outside of the ejection head 32 via the ink supply port 324. The ink supply port 324 and the ink discharge port 325 that communicate the ink storage chamber 322 and the outside are both disposed in the upper portion of the ink storage chamber 322. The ink storage chamber 322 and each of the plurality of ink chambers 323 communicate with each other via a communication port 326. Accordingly, when the pressure in the ink chamber 323 decreases, ink is supplied from the ink storage chamber 322 to the ink chamber 323.

  The ink chamber 323 is secondarily filled with ink in the ejection head 32. In FIG. 3, six ink chambers 323 are shown for convenience, but in the actual ejection head 32, ink chambers 323 are provided for each of a large number of nozzles 33.

  A nozzle 33 is provided at each lower end of the ink chamber 323. The nozzle 33 is a small hole that communicates the ink chamber 323 with the external space. When ink is not ejected, the ink surface forms a meniscus inside the nozzle 33. The lower end portion of the nozzle 33 is disposed so as to be exposed on the lower surface of the casing 321.

  A pressure generating element 327 is disposed on each wall surface of the ink chamber 323. The pressure generating element 327 is an in-head pressurizing mechanism that pressurizes ink stored in the ink chamber 323.

  The discharge head 32 of this embodiment is a so-called piezo-type discharge head. Therefore, a piezoelectric element is used for the pressure generating element 327 of the present embodiment. When an ejection signal that is an electrical signal is sent from the control unit 10 to the pressure generating element 327, the pressure generating element 327 is deformed and pressure is applied to the ink filled in the ink chamber 323. When the pressure in the ink chamber 323 increases, the ink in the ink chamber 323 is ejected from the nozzle 33 as droplets.

  The head of the present invention is not limited to the piezo method. For example, a so-called thermal-type ejection head that uses a heater as the pressure generating element to heat the liquid in the pressure chamber to generate bubbles to increase the pressure in the pressure chamber may be used.

  The UV lamp 40 irradiates ultraviolet rays on the upper surface side of the printing paper 9 conveyed by the conveyance mechanism 20 on the downstream side of the five head units 30. The ink droplets ejected on the printing paper 9 are cured by irradiation with ultraviolet rays. As a result, the image is fixed on the printing paper 9.

  The printing apparatus 1 includes five ink supply units 50 corresponding to the five head units 30 respectively. Since the structures of the five ink supply units 50 are substantially the same, the structure of one ink supply unit 50 will be described below.

  As shown in FIG. 3, the ink supply unit 50 includes a main tank 51, a supply pump 52, a sub tank 53, a reflux pump 54, and a pipe 55. The pipe 55 includes a first supply pipe 551, a second supply pipe 552, a plurality of third supply pipes 553, a plurality of first return pipes 554, and a second return pipe 555.

  The main tank 51 is an ink storage unit that stores ink. The volume of ink that can be stored in the main tank 51 is larger than the volume of ink that can be stored in the sub tank 53.

  The first supply pipe 551 is a pipe that connects the main tank 51 and the sub tank. One end of the first supply pipe 551 is connected to the inside of the main tank 51 in the vicinity of the lower end portion of the main tank 51. The other end of the first supply pipe 551 is connected to the inside of the sub tank 53.

  A first on-off valve 556, a supply pump 52, and a filter 557 are interposed in the first supply pipe 551. The first on-off valve 556 is disposed between the main tank 51 and the supply pump 52. The filter 557 is disposed between the supply pump 52 and the sub tank 53.

  The supply pump 52 is liquid feeding means for sending ink from the main tank 51 to the sub tank 53. The supply pump 52 is inserted in the first supply pipe 551. The supply pump 52 generates an ink flow from the main tank 51 to the sub tank 53 in the first supply pipe 551 in accordance with an operation signal from the control unit 10. Accordingly, the ink stored in the main tank 51 is supplied to the sub tank 53 via the first supply pipe 551.

  When the first on-off valve 556 is in the closed state, the communication of the first supply pipe 551 is blocked. That is, when the first on-off valve 556 is in the closed state, the communication between the main tank 51 and the sub tank 53 is blocked. On the other hand, when the 1st on-off valve 556 is an open state, the communication of the 1st supply piping 551 is ensured. The first on-off valve 556 is normally closed, and is opened only when the supply pump 52 is operated to supply ink from the main tank 51 to the sub tank 53. Thereby, it is possible to prevent the pressure fluctuation in the sub tank 53 from affecting the main tank 51.

  The filter 557 removes solid components and foreign matters of ink that passes through the first supply pipe 551. Thereby, it is suppressed that solid components and foreign matters are mixed in the ink supplied to the sub tank 53 and the ejection head 32. The filter 557 may be disposed at a place other than between the supply pump 52 and the sub tank 53 as long as the filter 557 is inserted in the first supply pipe 551.

  The sub tank 53 is a tank that temporarily stores ink. The sub tank 53 supplies the ink stored therein to each ejection head 32. The sub tank 53 includes a liquid level sensor 531. Ink is stored in the lower part of the sub tank 53, and the upper part of the sub tank 53 is filled with clean air.

  The liquid level sensor 531 is a sensor that detects the liquid level height of the ink stored in the sub tank 53. Based on the signal from the liquid level sensor 531, the control unit 10 detects the liquid level of the ink in the sub tank 53 and determines whether or not to supply ink to the sub tank 53. When supplying ink from the main tank 51 to the sub tank 53, the control unit 10 opens the first on-off valve 556 and operates the supply pump 52. When the supply of ink from the main tank 51 to the sub tank 53 is stopped, the control unit 10 stops the supply pump 52 and closes the first on-off valve 556.

  The second supply pipe 552 and the plurality of third supply pipes 553 connect the sub tank 53 and each of the plurality of discharge heads 32. That is, the sub tank 53 is connected to each discharge head 32 via the second supply pipe 552 and each third supply pipe 553.

  One end of the second supply pipe 552 is connected to the inside of the sub tank 53 in the vicinity of the lower end portion of the sub tank 53. The other end of the second supply pipe 552 is connected to one end of a plurality of third supply pipes 553. The other ends of the plurality of third supply pipes 553 are each connected to the ink supply port 324 of the ejection head 32. Thereby, the ink stored in the sub tank 53 is supplied to the ink storage chamber 322 of the ejection head 32 via the second supply pipe 552, the third supply pipe 553, and the ink supply port 324.

  As described above, the sub tank 53 is indirectly connected to the ink storage chamber 322 and the ink chamber 323 of the ejection head 32 via the second supply pipe 552 and the third supply pipe 553. Therefore, the pressure in the discharge head 32 can be adjusted by adjusting the pressure in the sub tank 53.

  The plurality of first return pipes 554 and the second return pipe 555 connect each of the plurality of discharge heads 32 to the main tank 51. One end of each of the plurality of first reflux pipes 554 is connected to the ink discharge port 325 of each ejection head 32. Further, the other ends of the plurality of first reflux pipes 554 are connected to one end of the second reflux pipe 555. The other end of the second reflux pipe 555 is connected in communication with the inside of the main tank 51.

  A second on-off valve 558 is interposed in each first return pipe 554. When the second on-off valve 558 is in the closed state, the communication of the first return pipe 554 through which the second on-off valve 558 is inserted is blocked. That is, when the second on-off valve 558 is in the closed state, the communication between the ink storage chamber 322 of the corresponding ejection head 32 and the second reflux pipe 555 is blocked. On the other hand, when the 2nd on-off valve 558 is an open state, the communication of the 1st return piping 554 by which the said 2nd on-off valve 558 is inserted is ensured. That is, when the second on-off valve 558 is in the open state, communication between the ink storage chamber 322 of the corresponding ejection head 32 and the second reflux pipe 555 is ensured.

  A reflux pump 54 and a third on-off valve 559 are inserted in the second reflux pipe 555. The third on-off valve 559 is disposed between the reflux pump 54 and the main tank 51.

  The reflux pump 54 is liquid feeding means for feeding ink from the ink storage chamber 322 of each discharge head 32 to the main tank 51. The reflux pump 54 is inserted in the second reflux pipe 555. The reflux pump 54 generates an ink flow from each first reflux pipe 554 toward the main tank 51 inside the second reflux pipe 555 in accordance with an operation signal from the control unit 10. As a result, the ink stored in the ink storage chamber 322 of each ejection head 32 is returned to the main tank 51 via the first return pipe 554 and the second return pipe 555.

  When the third on-off valve 559 is in the closed state, the communication of the second reflux pipe 555 is blocked. That is, when the third on-off valve 559 is in the closed state, the communication between each first return pipe 554 and the main tank 51 is blocked. On the other hand, when the 3rd on-off valve 559 is an open state, the communication of the 2nd recirculation | reflux piping 555 is ensured. The third on-off valve 559 is normally closed, and is opened only when the reflux pump 54 is operated to return the ink from each discharge head 32 to the main tank 51.

  As described above, the second opening / closing valve 558 is provided in each first return pipe 554, whereby ink can be returned to the individual ejection heads 32. When the ink is returned from some of the ejection heads 32 to the main tank 51, the second on-off valve 558 and the third on-off valve 559 corresponding to the target ejection head 32 are opened, and The other second on-off valve 558 is closed, and the reflux pump 54 is operated.

  Thus, the main tank 51, the supply pump 52, the reflux pump 54, the first supply pipe 551, the plurality of first return pipes 554, the second return pipe 555, the first on-off valve 556, the second on-off valve 558, and the third The on-off valve 559 constitutes an ink reflux means 500 that feeds ink from the ejection head 32 to the sub tank 53.

  The pressure adjusting unit 60 controls the pressure in the sub tank 53 and the discharge head 32. The pressure adjustment unit 60 includes a first main pipe 61, a buffer tank 62, a second main pipe 63, an air release part 64, an exhaust part 65, and a pressure sensor 66. The atmosphere release unit 64 includes an atmosphere release pipe 641 and an atmosphere release control valve 642. The exhaust unit 65 includes an exhaust pipe 651, an exhaust pump 652, and an exhaust control valve 653.

  One end of the first main pipe 61 is connected to the inside of the sub tank 53 in the upper part of the sub tank 53. In the subtank 53, the ink level is positioned near the level sensor 531. Therefore, one end of the first main pipe 61 is not in contact with the ink in the sub tank 53 and is disposed in the gas above the sub tank 53. The other end of the first main pipe 61 is connected to the inside of the buffer tank 62.

  The buffer tank 62 is a sealed tank filled with gas. The pressure sensor 66 measures the pressure in the buffer tank 62. Here, when the inside of the sub tank 53 and the inside of the buffer tank 62 communicate with each other via the first main pipe 61, the pressure in the sub tank 53 and the pressure in the buffer tank 62 become substantially the same. For this reason, the pressure sensor 66 indirectly measures the pressure in the sub tank 53.

  Note that the sub tank 53 may be connected to the atmosphere opening portion 64 and the exhaust portion 65 without the buffer tank 62 interposed therebetween. In that case, the pressure sensor 66 may measure the pressure in the sub tank 53 in the upper part of the sub tank 53. As described above, when the pressure sensor 66 directly measures the pressure in the sub tank 53, noise is likely to be generated in the measurement value of the pressure sensor 66 due to the pulsation of the supply pump 52 when the supply pump 52 is operated. When the buffer tank 62 is provided and the pressure sensor 66 measures the pressure in the buffer tank 62 as in this embodiment, noise due to the pulsation of the supply pump 52 can be reduced.

  One end of the second main pipe 63 is connected to the inside of the buffer tank 62. The other end of the second main pipe 63 is connected to one end of the air release pipe 641 and one end of the exhaust pipe 651. In other words, the atmosphere opening part 64 and the exhaust part 65 are connected to the other end of the second main pipe 63. Thereby, the buffer tank 62 is connected to the atmosphere opening part 64 and the exhaust part 65.

  One end of the air release pipe 641 is connected to the other end of the second main pipe 63. The other end of the air release pipe 641 is open to the atmosphere. An air release control valve 642 is inserted in the air release pipe 641. The atmosphere release control valve 642 switches the sub tank 53 and the outside between a communication state and a cutoff state. When the atmosphere release control valve 642 is in the open state, the second main pipe 63 is opened to the atmosphere. That is, when the atmosphere release control valve 642 is in the open state, the sub tank 53 and the buffer tank 62 are communicated with the outside and released to the atmosphere. Further, when the atmosphere release control valve 642 is in a closed state, the second main pipe 63 and the outside are blocked.

  Therefore, when the pressure in the sub tank 53 is higher than the atmospheric pressure and the pressure in the sub tank 53 is to be lowered, the control unit 10 opens the atmosphere release control valve 642. Then, the pressure in the sub tank 53 and the buffer tank 62 can be quickly reduced to atmospheric pressure.

  In addition, when the desired pressure is a negative pressure lower than the atmospheric pressure, the pressure in the sub tank 53 is lower than the desired pressure, and the pressure in the sub tank 53 is to be increased, the control unit 10 performs air release control. The valve 642 is opened for a certain time. Then, the pressure in the sub tank 53 and the buffer tank 62 can be brought close to the atmospheric pressure, and the pressure can be increased.

  One end of the exhaust pipe 651 is connected in communication with the other end of the second main pipe 63. An exhaust pump 652 is connected to the other end of the exhaust pipe 651. The exhaust pump 652 is an airflow generating unit that exhausts the gas in the exhaust pipe 651. An exhaust control valve 653 is inserted in the exhaust pipe 651. When the exhaust control valve 653 is in the open state, the second main pipe 63 and the exhaust pump 652 communicate with each other. Further, when the exhaust control valve 653 is closed, the communication between the second main pipe 63 and the exhaust pump 652 is blocked.

  Therefore, when the exhaust control valve 653 is opened and the exhaust pump 652 is driven, the gas in the sub tank 53 and the buffer tank 62 is exhausted through the exhaust pipe 651. As a result, the pressure in the sub tank 53 can be reduced to a negative pressure. That is, the exhaust part 65 can depressurize the sub tank 53.

  In the printing process and the standby time, the pressure in the ink chamber 323 is adjusted to a pressure at which an ink meniscus is formed in the nozzle 33 (hereinafter referred to as a meniscus pressure). In the present embodiment, since the ink chamber 323 is disposed below the ink storage chamber 322, it is necessary to set the pressure in the sub tank 53 so that the pressure in the ink storage chamber 322 becomes negative. When the pressure in the ink chamber 323 is higher than the meniscus pressure, the control unit 10 opens the exhaust control valve 653 and drives the exhaust pump 652 to reduce the pressure in the sub tank 53 to the meniscus pressure.

  When the printing apparatus 1 performs a printing process, ink droplets are ejected from the plurality of ejection heads 32 of each head unit 30 onto the upper surface of the printing paper 9 while the printing paper 9 is conveyed by the conveyance mechanism 20. Each head unit 30 is provided with a plurality of nozzles 33 for ejecting ink droplets at positions opposed to substantially the entire width of the upper surface of the printing paper 9. For this reason, each head unit 30 can eject ink droplets over substantially the entire width of the upper surface of the printing paper 9.

  By sequentially performing such ink droplet ejection processing in the five head units 30 in charge of each color, a multicolor pattern is formed on the upper surface of the printing paper 9.

  The operation unit 70 includes a display unit 71 and an input unit 72. The display unit 71 displays information such as the operating status of the printing apparatus 1 input from the control unit 10. The operator can input a command from the input unit 72 to the control unit 10. As the display unit 71, for example, a liquid crystal display is used. For the input unit 72, for example, a keyboard or a mouse is used. The display unit 71 is provided with a speaker 73. The speaker 73 constitutes a notification unit that notifies an operator of an error using voice in accordance with a command from the control unit 10. The display unit 71 may constitute a notification unit that displays characters or images and notifies an operator of an error.

  In the operation unit 70 according to the present embodiment, the display unit 71 and the input unit 72 are separate devices independent of the printing apparatus 1, but the touch panel type in which the display unit 71 and the input unit 72 are integrated. The operation unit 70 may be attached to the main body of the printing apparatus 1.

  The control unit 10 is a part for controlling the operation of each unit in the printing apparatus 1. As conceptually shown in FIG. 1, the control unit 10 of the present embodiment is configured by a computer having an arithmetic processing unit 11 such as a CPU, a memory 12 such as a RAM, and a storage unit 13 such as a hard disk drive. Yes. Further, as shown in FIG. 4, the control unit 10 includes the transport mechanism 20, the pressure generating elements 327 of the five head units 30, the UV lamp 40, the supply pump 52, the liquid level sensor 531, the reflux pump 54, the first The on-off valve 556, the second on-off valve 558, the third on-off valve 559, the atmosphere release control valve 642, the exhaust pump 652, the exhaust control valve 653, the pressure sensor 66, the display unit 71 and the input unit 72 are electrically connected to each other. ing.

  The control unit 10 temporarily reads the computer program 131 and data 132 stored in the storage unit 13 into the memory 12, and the arithmetic processing unit 11 performs arithmetic processing based on the computer program 131 and data 132. The operation of each unit in the printing apparatus 1 is controlled. Thereby, the printing process in the printing apparatus 1 and the ink circulation process described later proceed. In addition, the control part 10 may be comprised with the electronic circuit.

  The control unit 10 includes an operation detection unit 101 and an error detection unit 102 as processing units realized on software. That is, the operation detection unit 101 and the error detection unit 102 are realized by the arithmetic processing unit 11, the memory 12, and the storage unit 13 described above. The operation detection unit 101 detects the number or frequency of negative pressure reduction processing performed by the pressure adjustment unit 60. The error detection unit 102 determines whether the ink reflux unit 500 is operating normally based on the detection signal from the operation detection unit 101.

<2. About ink circulation process>
Next, the ink circulation process in the printing apparatus 1 will be described with reference to FIG. FIG. 5 is a flowchart showing the flow of the ink circulation process of the present embodiment.

  In the printing apparatus 1, as described above, ultraviolet curable UV ink is used. White (W) UV ink contains titanium oxide which is a sedimentation component. For this reason, the white (W) UV ink is more likely to settle and aggregate inside the ejection head 32 and inside the conduit through which the ink passes, as compared with other types of ink.

  Therefore, the printing apparatus 1 periodically performs an ink circulation process on at least the white (W) head unit 30 and the ink supply unit 50 during a period when the printing process is not performed. For example, an ink circulation process of 3 minutes per time is performed every 5 minutes.

  The “period in which the printing process is not performed” includes not only a period in which all the head units 30 are not performing the printing process but also a period in which the target head unit 30 is not used in the printing process. In other words, even when the printing process is performed using the other four colors, when the white (W) head unit 30 is not used, the white (W) head unit 30 and the ink supply unit 50 are An ink circulation process is performed.

  As shown in FIG. 5, in the ink circulation process, first, the control unit 10 starts counting the number of negative pressure reduction processes (step S101). Specifically, the operation detection unit 101 of the control unit 10 starts detecting the number of negative pressure reduction processes performed by the pressure adjustment unit 60. Then, the control unit 10 sets the head number n to 1 (step S102). In this printing apparatus 1, the number of heads N is 6 because the number of ejection heads included in one head unit 30 is six.

  Next, the control unit 10 circulates ink from the nth ejection head 32 to the main tank 51 (step S103). Specifically, the control unit 10 opens the second on-off valve 558 and the third on-off valve 559 corresponding to the nth discharge head, and operates the reflux pump 54. Then, after a predetermined time has elapsed, the reflux pump 54 is stopped, and the opened second open / close valve 558 and the third open / close valve 559 are closed. In the present embodiment, the control unit 10 performs such a reflux operation several times in step S103.

  When the circulation operation is performed, the ink is discharged from the ejection head 32. As a result, if the ink is normally circulated, the pressure in the ejection head 32, the sub tank 53, and the buffer tank 62 is reduced.

  Here, during the ink circulation process and the printing process, the control unit 10 causes the pressure adjustment unit 60 to perform the meniscus control process. Thereby, the pressure in the ejection head 32 is controlled to be a meniscus pressure. In the present embodiment, the negative pressure reduction process and the positive pressure reduction process are performed, so that the pressure in the ejection head 32 is controlled to be within a certain range.

  FIG. 6 is a flowchart showing the flow of the meniscus control process of the present embodiment. As shown in FIG. 6, in the meniscus control step, it is determined whether or not the pressure value measured by the pressure sensor 66 is smaller than a predetermined lower limit value (step S201).

  If the control unit 10 determines in step S201 that the pressure value measured by the pressure sensor 66 is smaller than a predetermined lower limit value, a negative pressure reduction process is performed (step S202). Specifically, the control unit 10 opens the atmosphere release control valve 642 and closes it after a predetermined time has elapsed. Thereby, the sub tank 53 and the buffer tank 62 are opened to the atmosphere for a predetermined time, and the pressure in the discharge head 32, the sub tank 53, and the buffer tank 62 increases. When step S202 ends, the process returns to step S201.

  On the other hand, when the control unit 10 determines in step S201 that the pressure value measured by the pressure sensor 66 is greater than the predetermined lower limit value, the process proceeds to step S203. Then, it is determined whether or not the pressure value measured by the pressure sensor 66 is greater than a predetermined upper limit value (step S203).

  If the control unit 10 determines in step S203 that the pressure value measured by the pressure sensor 66 is greater than a predetermined upper limit value, a positive pressure reduction process is performed (step S204). Specifically, the control unit 10 opens the exhaust control valve 653 and operates the exhaust pump 652. Then, after a predetermined time has elapsed, the exhaust pump 652 is stopped and the exhaust control valve 653 is closed. Thereby, the gas in the sub tank 53 and the buffer tank 62 is discharged, and the pressure in the discharge head 32, the sub tank 53, and the buffer tank 62 decreases. When step S204 ends, the process returns to step S201.

  As described above, when the reflux operation is performed in step S103, the pressure in the ejection head 32, the sub tank 53, and the buffer tank 62 decreases if the ink circulates normally. For this reason, if the ink circulates normally, the control unit 10 should perform the negative pressure reduction process with the reflux operation in step S103. Therefore, the control unit 10 can determine whether or not the ink is normally circulated by detecting the number of times of the negative pressure reduction processing during steps S101 to S106.

  Subsequent to step S103, the control unit 10 increments the head number n (step S104). Thereafter, the control unit 10 determines whether or not the head number n is larger than the head number N (step S105).

  In step S105, when the control unit 10 determines that the head number n is equal to or less than the number N of heads, the control unit 10 returns to step S103 and performs a reflux operation for the next ejection head 32. On the other hand, if the control unit 10 determines in step S105 that the head number n is larger than the head number N, the control unit 10 counts the negative pressure reduction processing by the operation detection unit 101, assuming that the reflux operation for all the ejection heads 32 is completed. The process ends (step S106).

  Thereafter, the error detection unit 102 of the control unit 10 determines whether or not the number of negative pressure reduction processes between step S101 to step S106 is included in a predetermined range (step S107). That is, the error detection unit 102 determines whether or not the ink reflux unit 500 is operating normally based on the detection signal from the operation detection unit 101 when the reflux pump 54 is operating.

  If the error detection unit 102 determines in step S107 that the number of negative pressure reduction processes is within the predetermined range, the process proceeds to step S108. In other words, the error detection unit 102 determines that the ink reflux unit 500 is operating normally when the number of negative pressure reduction processes matches a predetermined condition. In this case, the control unit 10 determines that the ink is normally circulated, and continues the ink circulation process. Then, the control unit 10 performs an ink supply operation to the sub tank 53 (step S108).

  In step S <b> 108, the control unit 10 first determines whether it is necessary to supply ink to the sub tank 53 based on the detection signal from the liquid level sensor 531. When determining that ink supply is necessary, the control unit 10 opens the first on-off valve 556 and operates the supply pump 52. When it is determined that the ink level in the sub tank 53 has reached a predetermined upper limit based on the detection signal from the liquid level sensor 531, the supply pump 52 is stopped and the first on-off valve 556 is closed. And Thereafter, the ink circulation process is terminated. If it is determined in step S108 that the ink supply is unnecessary, the control unit 10 normally ends the ink circulation process.

  On the other hand, in step S107, when the error detection unit 102 determines that the number of negative pressure reduction processes is not included in the predetermined range, the control unit 10 determines that the ink is not normally circulated. That is, the error detection unit 102 determines that the ink reflux unit 500 is not operating normally when the number of negative pressure reduction processes does not match a predetermined condition. When an error is detected in this way, the control unit 10 performs error notification by the error notification unit. In the present embodiment, the control unit 10 notifies the operator of an error using sound from the speaker 73 provided in the display unit 71.

  As described above, in the printing apparatus 1, ink is recirculated from the ejection head 32 to the sub tank 53 via the main tank 51 in the ink circulation process. On the other hand, while performing such a reflux, the pressure in the sub tank 53 is measured by the pressure sensor 66 via the buffer tank 62, and when the pressure falls below a predetermined value, a negative pressure reduction process is performed. Then, the control unit 10 detects the number of negative pressure reduction processes during execution of the circulation process, and determines whether the ink reflux unit 500 is operating normally based on the detected number of times. That is, while performing the ink circulation process, it is determined whether or not the ink is normally circulated by detecting the number or frequency of the negative pressure reduction processing that the pressure adjustment unit 60 performs as part of the meniscus control.

  Thereby, it is possible to confirm whether or not the ink is normally circulated without providing a pressure sensor in the ink circulation path. Further, it is possible to confirm whether or not the ink is normally circulated without adding new parts.

<3. Modification>
Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.

  FIG. 7 is a flowchart showing the flow of an ink circulation process according to a modification. In the example of FIG. 7, the control unit 10 first sets the head number n to 1 (step S301). Then, the operation detection unit 101 of the control unit 10 starts counting the number of negative pressure reduction processes (step S302). Next, the controller 10 circulates ink from the nth ejection head 32 to the main tank 51 (step S303). And the count of the negative pressure reduction process by the operation | movement detection part 101 is complete | finished (step S304).

  Thereafter, the error detection unit 102 of the control unit 10 determines whether or not the number of times of negative pressure reduction processing between step S302 and step S305 is included in a predetermined range (step S305). In step S305, when the error detection unit 102 determines that the number of negative pressure reduction processes is within a predetermined range, the process proceeds to step S306. On the other hand, when the error detection unit 102 determines in step S305 that the number of negative pressure reduction processes is not included in the predetermined range, an error is notified.

  In step S306, the control unit 10 increments the head number n. Subsequently, the control unit 10 determines whether or not the head number n is larger than the head number N (step S307). In step S307, when the control unit 10 determines that the head number n is equal to or less than the head number N, the control unit 10 returns to step S302 and performs the reflux operation for the next ejection head 32. On the other hand, when the control unit 10 determines in step S307 that the head number n is larger than the head number N, the process proceeds to step S308, and the ink supply operation to the sub tank 53 is performed.

  As in the example of FIG. 7, each time the reflux operation for each ejection head 32 is completed, it may be determined whether or not the number of negative pressure reduction processes in the ink circulation process is within a predetermined range.

  FIG. 8 is a flowchart showing the flow of an ink circulation process according to another modification. In the example of FIG. 8, first, the operation detection unit 101 of the control unit 10 starts counting the number of negative pressure reduction processes (step S401). Then, the control unit 10 sets the head number n to 1 (step S402). Next, the control unit 10 circulates ink from the nth ejection head 32 to the main tank 51 (step S403). Subsequently, the control unit 10 performs an ink supply operation to the sub tank 53 (step S404). Thereafter, the control unit 10 increments the head number n (step S405).

  When step S405 is completed, the control unit 10 determines whether or not the head number n is larger than the head number N (step S406). In step S406, when the control unit 10 determines that the head number n is equal to or less than the number N of heads, the control unit 10 returns to step S403 and performs the reflux operation for the next ejection head 32. On the other hand, when the control unit 10 determines in step S406 that the head number n is larger than the head number N, the control unit 10 proceeds to step S407 and ends the negative pressure reduction processing count by the operation detection unit 101.

  Thereafter, the error detection unit 102 of the control unit 10 determines whether or not the number of negative pressure reduction processes between step S401 to step S407 is included in a predetermined range (step S408). In step S408, when the error detection unit 102 determines that the number of negative pressure reduction processes is within the predetermined range, the control unit 10 normally ends the ink circulation process. On the other hand, in step S408, when the error detection unit 102 determines that the number of negative pressure reduction processes is not included in the predetermined range, an error is notified.

  As in the example of FIG. 8, the ink supply operation to the sub tank 53 may be performed every time the reflux operation for each ejection head 32 is completed. In particular, when a large amount of ink is recirculated in the recirculation operation for each discharge head 32, or when the number of the discharge heads 32 is large, when the recirculation operation for one or a predetermined number of the discharge heads 32 is completed, the sub tank The ink supply operation to 53 is preferably performed.

  Moreover, although the printing apparatus of the above embodiment has five head units, the number of head units may be 1 to 4, or 6 or more.

  Moreover, although the ultraviolet curable UV ink was used in the printing apparatus of the above embodiment, the present invention is not limited to this. Instead of the UV ink, other types of ink such as oil-based ink or water-based ink dried by hot air may be used. In that case, the printing apparatus may not have a UV lamp.

  Further, the printing apparatus of the above-described embodiment prints an image on printing paper as a recording medium. However, the printing apparatus of the present invention may print a pattern such as an image on a sheet-like recording medium (for example, a resin film) other than general paper.

  Moreover, you may combine suitably each element which appeared in said embodiment and modification in the range which does not produce inconsistency.

DESCRIPTION OF SYMBOLS 1 Inkjet printer 10 Control part 30 Head unit 32 Discharge head 33 Nozzle 50 Ink supply part 51 Main tank 52 Supply pump 53 Sub tank 54 Reflux pump 60 Pressure adjustment part 64 Atmospheric release part 65 Exhaust part 66 Pressure sensor 73 Speaker 101 Operation | movement detection part 102 Error detector 641 Atmospheric release piping 642 Atmospheric release control valve 651 Exhaust piping

Claims (10)

A head having a plurality of nozzles for discharging ink to a recording medium;
A tank for storing the ink and supplying the ink to the head;
Ink reflux means for feeding the ink from the head to the tank;
A pressure adjusting unit for performing a negative pressure reduction process for increasing the pressure in the tank when the pressure in the tank becomes a predetermined value or less;
An operation detection unit that detects the number or frequency of the negative pressure reduction processing performed by the pressure adjustment unit;
Based on a detection signal from the operation detection unit, an error detection unit for determining whether or not the ink reflux means is operating normally;
An inkjet printer. The inkjet printer according to claim 1,
The pressure adjusting unit is
An open-air piping communicating the tank and the outside;
An atmosphere release valve that is inserted into the atmosphere release pipe and switches the tank and the outside between a communication state and a cutoff state;
Have
The said pressure adjustment part is an inkjet printer which performs the said negative pressure reduction process by open | releasing the said air release valve and releasing the said tank to air | atmosphere. The inkjet printer according to claim 1 or 2,
The error detection unit is an ink jet printer that determines that the ink reflux unit is not operating normally when the number of times or the frequency does not match a predetermined condition. An inkjet printer according to any one of claims 1 to 3,
The ink reflux means includes
An ink reservoir for storing the ink;
A reflux pump for feeding the ink from the head to the ink reservoir;
A supply pump for feeding the ink from the ink reservoir to the tank;
An inkjet printer. The inkjet printer according to claim 4,
The error detection unit is an ink jet printer that determines whether or not the ink reflux means is operating normally based on the detection signal when the reflux pump is operated. The inkjet printer according to any one of claims 1 to 5,
An ink jet printer having a plurality of the heads. The inkjet printer according to any one of claims 1 to 6,
An ink jet printer further comprising an error notifying unit for notifying an error when the error detecting unit determines that the ink reflux means is not operating normally. A head having a plurality of nozzles for discharging ink to a recording medium;
A tank for supplying the ink to the head;
Ink reflux means for feeding the ink from the head to the tank;
In the ink jet printer having the above, a liquid feeding state confirmation method for confirming a liquid feeding state of the ink from the head to the tank,
a) measuring the pressure in the tank while refluxing the ink from the head to the tank, and determining whether the pressure in the tank has become a predetermined value or less;
b) performing a negative pressure reduction process for increasing the pressure in the tank when the pressure in the tank becomes equal to or lower than the predetermined value during the execution of the step a);
c) Detecting the number or frequency of the negative pressure reduction processing during the execution of the step a), and determining whether or not the ink reflux means is operating normally based on the detected number or frequency. Process,
A liquid feeding state confirmation method. It is a liquid feeding state confirmation method of Claim 8, Comprising:
In step b)
The negative pressure reduction process is a process of opening the tank to the atmosphere.
How to check the delivery status. It is a liquid feeding state confirmation method of Claim 8 or Claim 9, Comprising:
In step c)
When the number of times or the frequency of the negative pressure reduction processing does not match a predetermined condition, it is determined that the ink return means is not operating normally;
How to check the delivery status.

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