JP2020179533A - Inkjet recording device and abnormality detection method - Google Patents

Abstract

To provide an inkjet recording device that can further readily return to a proper image recording operation, and to provide an abnormality detection method.SOLUTION: An inkjet recording device includes: a recording head with a nozzle for discharging ink; an ink storage chamber communicated to the nozzle; a pressure adjustment unit for operating to make internal pressure of the ink storage chamber negative pressure; and a determination unit for determining whether a liquid level of ink at the nozzle has any abnormality on the basis of pressure variation characteristics.SELECTED DRAWING: Figure 6

Description

The present invention relates to an inkjet recording device and an abnormality detection method.

There is an inkjet recording device that ejects ink from a nozzle to record an image or the like. By appropriately pushing and pulling the ink in the nozzle by applying pressure fluctuation to the ink in the ink flow path, the ink with an appropriate speed, liquid amount and droplet diameter is ejected from the nozzle and flies. ..

At this time, if the pressure applied to the ink is not properly maintained with respect to the atmospheric pressure, there is a problem that the ink ejection amount and the ejection speed vary, and the recorded image also varies in density and the like. On the other hand, a predetermined negative pressure, which is a reference pressure applied to the ink so that the ink does not leak from the nozzle during standby, is applied to the atmospheric pressure based on the pressure change of the negative pressure tank communicating with the ink cartridge. There is a technique for keeping the pressure constant (Patent Document 1).

JP-A-2010-155428

However, even if an attempt is made to apply an appropriate pressure fluctuation to the ink, if the liquid surface (meniscus) of the ink in the nozzle is not properly in contact with the wall surface, air is entrained with the pressure fluctuation and applied to the ink. The pressure does not properly propagate in the ink, causing an abnormality in the ink ejection. Since such an abnormality in the liquid level becomes worse when it occurs, there is a problem that the slower the detection, the larger the need for a large-scale response and the time and effort required.

An object of the present invention is to provide an inkjet recording device and an abnormality detection method capable of more easily returning to an appropriate image recording operation.

In order to achieve the above object, the invention according to claim 1 is
A recording head with a nozzle that ejects ink,
An ink storage chamber that communicates with the nozzle and
A pressure adjusting unit that operates to make the air pressure in the ink storage chamber negative.
A discriminant unit that determines the presence or absence of an abnormality in the ink liquid level in the nozzle based on the change characteristic of the atmospheric pressure,
It is an inkjet recording apparatus characterized by the above.

The invention according to claim 2 is the invention according to claim 1 in the inkjet recording apparatus according to claim 1.
The discriminating unit is characterized in that the presence or absence of the abnormality is discriminated according to the rate of change of the atmospheric pressure.

The invention according to claim 3 is the invention according to claim 2 in the inkjet recording apparatus according to claim 2.
A control unit that controls the operation of the pressure adjusting unit is provided.
The control unit starts the decompression operation by the pressure adjusting unit when the air pressure is larger than the first reference value, and stops the decompression operation when the air pressure is less than the second reference value smaller than the first reference value. Let me
The discriminating unit is characterized in that the abnormality is determined when the elapsed time from the stop to the start is shorter than the reference time.

The invention according to claim 4 is the invention according to claim 3 in the inkjet recording apparatus according to claim 3.
The pressure adjusting unit is characterized by having a fan that sucks air from the ink storage chamber.

The invention according to claim 5 is the invention according to claim 3 or 4.
It is characterized by including a storage unit for storing the reference time.

Further, the invention according to claim 6 is in the inkjet recording apparatus according to any one of claims 3 to 5.
An air storage chamber connected to the ink storage chamber to store air and
A switching unit that switches the presence or absence of the connection in the air storage chamber, and
With
The control unit is characterized in that the presence / absence of the connection by the switching unit is switched according to the operating status of the recording head.

The invention according to claim 7 is the invention according to claim 6 in the inkjet recording apparatus according to claim 6.
The control unit is characterized in that when the recording head is not performing the ink ejection operation, the switching unit is switched so that the connection of the air storage chamber is not made.

Further, the invention according to claim 8 is
Ink in the nozzle of an inkjet recording apparatus including a recording head having a nozzle for ejecting ink, an ink storage chamber communicating with the nozzle, and a pressure adjusting unit for operating the pressure in the ink storage chamber as a negative pressure. It is a method of detecting abnormalities in the liquid level of
A step of determining the presence or absence of an abnormality in the liquid level in the nozzle based on the change characteristic of the atmospheric pressure.
It is characterized by including.

According to the present invention, there is an effect that the inkjet recording apparatus can more easily return to the proper image recording operation.

It is a schematic diagram which looked at the structure of the inkjet recording apparatus from the front. It is a bottom view which shows the surface which faces the transport surface in a head unit. It is a figure explaining the ink supply path to a recording head. It is a block diagram which shows the functional structure of an inkjet recording apparatus. It is a figure which shows the example of the change of the atmospheric pressure in the ink tank. It is a figure which shows the example of the change of the atmospheric pressure in the ink tank. It is a flowchart which shows the control procedure of the liquid level state detection processing.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view of the configuration of the inkjet recording device 1 of the embodiment as viewed from the front.

The inkjet recording device 1 includes a medium supply unit 10, an image forming unit 20, a medium ejection unit 30, a control unit 40 (see FIG. 3), and the like. In the inkjet recording device 1, the recording medium M stored in the medium supply unit 10 is conveyed to the image forming unit 20 based on the control operation by the control unit 40, and after the image is formed, it is discharged to the medium discharging unit 30. To.

The medium supply unit 10 includes a medium supply tray 11, a supply transfer unit 12, and the like.
The medium supply tray 11 is a plate-shaped member provided so that one or more recording media M can be placed. The medium supply tray 11 moves up and down according to the amount of the mounted recording medium M, and the uppermost recording medium M is held at the transfer start position by the supply transfer unit 12.
As the recording medium M, various media such as printing papers, cells, films and fabrics having various thicknesses are used. The recording medium M may have a surface made of a non-absorbent material through which the ink does not penetrate.
The supply transport unit 12 includes a plurality of (for example, two) rollers 121 and 122, a ring-shaped belt 123 supported by the rollers 121 and 122 on the inner surface thereof, and a recording medium M placed on the medium supply tray 11. It has a supply unit (not shown) that delivers the top one to the belt 123. The supply transport unit 12 conveys the recording medium M delivered on the belt 123 by the supply unit according to the orbital movement of the belt 123 due to the rotation of the rollers 121 and 122, and sends the recording medium M to the image forming unit 20.

The image forming unit 20 includes an image forming drum 21, a delivery unit 22, a head unit 23, a fixing unit 24, a delivery unit 25, and the like.

The image forming drum 21 has a cylindrical outer peripheral shape, supports the recording medium M on the outer peripheral surface (conveying surface), and conveys the recording medium M by a conveying path corresponding to the rotation operation thereof. A heater is provided on the inner surface side of the image forming drum 21, and the transport surface can be heated so that the recording medium M placed on the transport surface reaches a predetermined set temperature.

The delivery unit 22 delivers the recording medium M delivered from the supply / transport unit 12 to the image forming drum 21. The delivery unit 22 is provided at a position between the supply / transfer unit 12 of the medium supply unit 10 and the image forming drum 21. The delivery unit 22 has a claw portion 221 that grips one end of the recording medium M sent by the supply / transport unit 12, a cylindrical transfer drum 222 that guides the recording medium M gripped by the claw portion 221 and the like. The recording medium M acquired from the supply / transport unit 12 by the claw portion 221 moves along the outer peripheral surface of the transfer drum 222 that rotates when sent to the transfer drum 222, and is guided to the outer peripheral surface of the image forming drum 21 as it is. Delivered.

The head unit 23 moves relative to the head unit 23 from a plurality of nozzle openings provided on the ink ejection surface facing the recording medium M in response to the rotation of the image forming drum 21 on which the recording medium M is supported. An image is formed by ejecting ink droplets to various places (medium to be landed with ink). In the inkjet recording device 1 of the present embodiment, four head units 23 are arranged at predetermined intervals, separated from the outer peripheral surface of the image forming drum 21 by a preset distance. The four head units 23 output inks of four CMYK colors (cyan, magenta, yellow, and black), respectively. Here, each color ink of C, M, Y, and K is ejected in order from the upstream side in the transport direction of the recording medium M. Any ink can be used, but here, an ink that undergoes a phase change between a sol state and a gel state depending on the temperature and is fixed by irradiation with a predetermined energy ray, for example, ultraviolet rays. Used. When the ink ejected from the head unit 23 in the sol state lands on the recording medium M, the temperature drops and gels rapidly to increase the viscosity, and the ink is transferred to the recording medium M by the ultraviolet rays emitted from the fixing portion 24. Settle.
Each of the head units 23 is, here, a line head capable of forming an image over the image recording width on the recording medium M in combination with the rotation of the image forming drum 21.

The fixing unit 24 irradiates the surface of the recording medium M with a predetermined energy ray, here, ultraviolet rays as described above. The fixing unit 24 includes, for example, an LED lamp that emits ultraviolet rays. The fixing portion 24 is in the vicinity of the outer peripheral surface of the image forming drum 21, and after the ink is ejected from the head unit 23 onto the recording medium M conveyed by the rotation of the image forming drum 21, the recording medium M is used for the image. The recording medium M is arranged so as to be able to irradiate ultraviolet rays in a range before passing from the forming drum 21 to the delivery unit 25.

The delivery unit 25 conveys the recording medium M on which the ink is ejected and fixed from the image forming drum 21 to the medium discharge unit 30. The delivery unit 25 includes a plurality of (for example, two) rollers 251 and 252, a ring-shaped belt 253 supported by the rollers 251 and 252 on the inner surface, a cylindrical transfer roller 254, and the like. The delivery unit 25 guides the recording medium M on the image forming drum 21 onto the belt 253 by the delivery roller 254, and moves the delivered recording medium M together with the belt 253 that orbits as the rollers 251 and 252 rotate. As a result, it is conveyed and sent out to the medium discharge unit 30.

The medium discharging unit 30 stores the recording medium M after image recording sent out from the image forming unit 20 until it is taken out by the user. The medium discharge unit 30 has a plate-shaped medium discharge tray 31 on which the recording medium M conveyed by the delivery unit 25 is placed.

FIG. 2 is a bottom view showing a surface of the head unit 23 facing the transport surface.
Since the head units 23 of each color have the same shape and configuration, any one of them will be described here.

In the head unit 23, eight recording heads 231 are fixed here. On the bottom surface of each recording head 231, a plurality of nozzles N openings are arranged in the width direction at a predetermined nozzle pitch. The opening positions of the nozzles N may be different in the transport direction as long as they are arranged at predetermined intervals in the width direction. Here, in the recording head 231, the openings of the nozzles N are arranged in a houndstooth pattern. The number and size of the openings of the nozzle N shown in this figure are for the purpose of explanation, and as will be described later, the number and the size are actually larger than this, and the size is the arrangement range of the nozzle N in the width direction. Small enough compared to the width of.

The eight recording heads 231 included in one head unit 23 are arranged in a houndstooth pattern at different positions. Along with this, the arrangement ranges of the nozzle N in each recording head 231 in the width direction are located different from each other, and image recording can be performed in different recording ranges. The ends of the arrangement range of the nozzles N in the width direction of the adjacent recording heads 231 slightly overlap. Therefore, in the head unit 23, by combining the recording ranges in the width direction of each of the eight recording heads 231 at the above nozzle pitch over the entire width of the recording medium (there may be some margins at both ends) in the width direction. , It is possible to eject ink from a plurality of nozzles divided into each recording head 231.

FIG. 3 is a diagram illustrating an ink supply path to the recording head 231.
The ink that has flowed from the upstream tank (not shown) into the ink tank 70 (ink storage chamber communicating with the nozzle N) through the supply path 701 by the liquid feed pump 81 is supplied to each nozzle N of the recording head 231 via the inflow path 702. To. The number of recording heads 231 to which ink is supplied from the ink tank 70 does not have to be one. Here, the ink may be discharged through the discharge flow path 703 without discharging the ink from the nozzle N of the recording head 231. The discharged ink may be collected in the upstream tank and supplied to the recording head 231 again.

The ink tank 70 has no opening other than the pipe. An air layer A is provided in the ink tank 70, and a measuring unit 64 (pressure detecting unit) for measuring (detecting) the atmospheric pressure of the air layer A is provided.

The ink tank 70 is connected to the first solenoid valve 71 and the second solenoid valve 72 via a pipe 704. The first solenoid valve 71 is a solenoid valve that switches whether or not the pipe 704 communicates with the atmosphere. The second solenoid valve 72 is a solenoid valve that switches whether or not to communicate the pipe 704 with the suction pump 82. The suction pump 82 (pressure adjusting unit) sucks air from the pipe 704 to make the air pressure in the ink tank 70 a negative pressure.

The pipe 704 that branches between the second solenoid valve 72 and the suction pump 82 is connected to the third solenoid valve 73 (switching portion). The third solenoid valve 73 is a solenoid valve that switches whether or not the pipe 704 (ink tank 70) communicates with the air chamber 83 (air storage chamber) (whether or not it is connected). The air chamber 83 has a volume sufficiently larger than the volume of air in the air layer A of the ink tank 70, and stores air. When the second solenoid valve 72 and the third solenoid valve 73 are opened and connected to the ink tank 70, the air layer A of the air layer A corresponding to the increase or decrease of the ink in the ink tank 70 due to the ejection of ink from the recording head 231 or the like. Fluctuations in atmospheric pressure are suppressed.

FIG. 4 is a block diagram showing a functional configuration of the inkjet recording device 1 of the present embodiment.
In addition to the image forming unit 20, the measuring unit 64, the first solenoid valve 71, the second solenoid valve 72, the third solenoid valve 73, the liquid feed pump 81, and the suction pump 82, the inkjet recording device 1 includes a control unit 40. (It also operates as a discriminating unit), includes a transport drive unit 45, a storage unit 50, a communication unit 61, a display unit 62, an operation reception unit 63, a bus 90, and the like.

The image forming unit 20 includes a plurality of nozzles N, a head driving unit 28 for ejecting ink from the plurality of nozzles N, a fixing driving unit 29, and the like.

The head drive unit 28 operates a mechanism for applying pressure to the ink in the ink flow path that communicates with each nozzle N to supply ink, and causes the head unit 23 (head module 230, recording head 231) to perform a recording operation. Let me do it. For example, the head drive unit 28 generates a drive voltage signal for a piezoelectric element that deforms the wall surface of the pressurizing unit (pressure chamber) provided in the ink flow path and outputs the drive voltage signal to the piezoelectric element. The deformation of the piezoelectric element deforms the pressure chamber to give pressure fluctuations to the ink in a predetermined pattern, and accordingly, ink droplets of a desired amount of liquid are ejected from the opening of the nozzle N at a desired speed.

The fixing drive unit 29 outputs a drive signal to the fixing unit 24 to emit (emit) a predetermined energy ray (here, ultraviolet rays).

The control unit 40 controls the overall operation of the inkjet recording device 1 and controls the operation of each unit. The control unit 40 includes a CPU 41 (Central Processing Unit), a RAM 42 (Random Access Memory), and the like.

The CPU 41 performs various arithmetic processes and controls the transfer of the recording medium M, the supply of ink, the ejection of ink, the maintenance operation, and the like in the inkjet recording device 1. Further, the CPU 41 performs various processes related to image recording based on the image data, the status signal of each unit, the clock signal, and the like according to the program read from the storage unit 50.

The RAM 42 provides the CPU 41 with a working memory space and stores temporary data. The RAM 42 may include a non-volatile memory, and the data stored in the non-volatile memory and the data stored in the storage unit 50 are appropriately allocated.

The storage unit 50 stores job data related to image recording acquired from the outside via the communication unit 61, control programs and setting data related to various control operations of the control unit 40, and the like. A DRAM is mainly used as a configuration for temporarily storing job data and its processing data, and an HDD (Hard Disk Drive), a non-volatile memory, or the like is used as a configuration for storing control programs and setting data. Not limited to. For example, the job data may be stored in the non-volatile memory, or the initial program, the initial setting data, and the like may be stored in a mask ROM or the like that cannot be rewritten and updated. The control program includes a program 51 related to a liquid level state detection process for determining the presence or absence of an ink liquid level abnormality (meniscus abnormality).

Further, in the data stored in the storage unit 50, the reference time Tet (see FIG. 6) for determining the presence or absence of an abnormality in the liquid level state is predetermined and stored according to the presence or absence of the connection of the air chamber 83 and the like. 52 is included.

The transport drive unit 45 operates each unit that transports and moves the recording medium M, such as the supply transport unit 12, the image forming drum 21, the transfer unit 22, and the delivery unit 25. The transport drive unit 45 includes a motor that rotates each roller, drum, and the like, and also operates the claw unit 221. Of these, at least the image forming drum 21 and the transfer drive unit 45 form the transfer unit in the inkjet recording device 1 of the present embodiment.

The communication unit 61 is a communication interface that controls a communication operation with an external device. The communication interface includes one or a plurality of communication interfaces corresponding to various communication protocols such as a LAN card. The communication unit 61 acquires the original image data to be recorded and the setting data (job data) related to the image recording from the external device based on the control of the control unit 40, and also transmits the status information and the like to the external device. be able to.

The display unit 62 displays the status of the inkjet recording device 1 and the operation menu in response to the control signal from the control unit 40. The display unit 62 has a display screen such as a liquid crystal screen. Further, the display unit 62 may have an LED or the like used for the notification operation.

Further, the operation reception unit 63 receives the user's operation and outputs it to the control unit 40. The operation reception unit 63 has, for example, a touch sensor provided so as to overlap the display screen. The control unit 40 associates the menu content and position information displayed on the display screen with the user's touch operation type and position information received by the operation reception unit 63, and performs processing according to the operation by inkjet. A control operation is performed on each part of the recording device 1. The operation reception unit 63 may include a push button switch, a numeric keypad, or the like.

As described above, the measuring unit 64 is a barometric pressure sensor. As the atmospheric pressure sensor, a well-known one such as one using a piezoelectric element can be used. The measuring unit 64 may have ink resistance.

The first solenoid valve 71 to the third solenoid valve 73 are switched between opening and closing according to the control signal of the control unit 40, respectively.

The liquid feed pump 81 is a pump that feeds ink to be supplied to the ink tank 70. The type of the liquid feed pump 81 is not particularly limited, but is, for example, a diaphragm type pump or the like.

The suction pump 82 is provided with, for example, a fan, and sucks the air in the pipe 704 to the outside according to the rotational operation based on the control of the control unit 40. The rotation speed of the fan may be adjustable.

The bus 90 is a signal transmission path that electrically connects the control unit 40 and each of the above configurations to exchange signals.

Next, the back pressure control of the recording head 231 and the liquid level state in the nozzle N will be described.
In the inkjet recording device 1, the ink in the ink tank 70 is made lower than the atmospheric pressure by a predetermined pressure (for example, -3 kPa) to balance the ink in the nozzle N with the gravity and prevent the ink from leaking from the nozzle N. .. For this reason, when the atmospheric pressure measured by the measuring unit 64 is not within the reference range, the first solenoid valve 71 is opened to allow the atmosphere to flow in to raise the atmospheric pressure, or the second solenoid valve 72 is opened. The suction pump 82 can be operated in this state to lower the atmospheric pressure. In reality, since the ink tank 70 is not completely airtight, air gradually enters the ink tank 70 and the air pressure rises. Therefore, in the inkjet recording device 1, the suction pump 82 is operated at substantially constant intervals for a substantially constant time.

5 and 6 are diagrams showing an example of a change in atmospheric pressure in the ink tank 70. As shown in FIG. 5A, the operation of the suction pump 82 causes the suction pump 82 to operate when the pressure drops from the initial pressure (atmospheric pressure) to less than the lower limit PL (second reference value). It will be stopped. When the air pressure gradually rises during the time Te when the suction pump 82 is stopped and exceeds the upper limit PH (first reference value) larger than the lower limit PL (when it is larger than), The operation (decompression operation) of the suction pump 82 is started (restarted). Then, when the atmospheric pressure falls below the lower limit value PL in the suction operation during the time Ti, the operation of the suction pump 82 is stopped again. The upper limit value PH and the lower limit value PL may be variable values defined relative to the fluctuating atmospheric pressure. For this purpose, the measuring unit 64 may separately have a barometric pressure sensor for measuring the atmospheric pressure. The difference between the upper limit PH and the lower limit PL (for example, 0.1 kPa) is smaller than the difference between the atmospheric pressure and the lower limit PL (for example, 3 kPa as described above).

At this time, if the third solenoid valve 73 is opened, the sum of the volumes of the ink tank 70 and the air chamber 83 is greatly increased. Therefore, as shown in FIG. 5B, the third solenoid valve 73 is closed. Compared to the case where it is (thick line), the change in atmospheric pressure becomes relatively gentle (thin line). Since it is preferable that the change in back pressure is small during the ink ejection operation, the third solenoid valve 73 may be opened. On the contrary, since the abnormality can be detected more quickly when the change is larger, the third solenoid valve 73 may be closed when the ink ejection operation is not performed. That is, the opening / closing of the third solenoid valve 73 (whether or not the air chamber 83 is connected) can be switched according to the presence or absence of the ink ejection operation (operating status of the recording head). The suction pump 82 may be appropriately operated so that the back pressure does not become positive when the third solenoid valve 73 is opened in response to a change in atmospheric pressure while the third solenoid valve 73 is closed.

When an abnormality occurs in the liquid level of the ink in the nozzle N and the meniscus is torn, the liquid level does not cover the entire cross section of the nozzle N, so that a gap is created and air enters. As a result, as shown in FIG. 6, the air that has entered flows into the ink tank 70, and the air pressure (atmospheric pressure) in the ink tank 70 rises normally (solid line) faster, and the air pressure falls slower (solid line). Dashed line). Therefore, based on such a change characteristic of the air pressure in the ink tank 70, here, in particular, the rate of increase (change rate) of the air pressure of the ink tank 70, that is, the air pressure is the upper limit from the lower limit value PL (second reference value). When the elapsed time for increasing to the value PH (first reference value) is shorter than the reference time Tet, it can be determined that an abnormality has occurred in the liquid level of the ink. The reference time Tet is not particularly limited and may be adjusted by the number of nozzles N to which ink is supplied from one ink tank 70, but may be set to, for example, 1/3 of the normal time Te. .. Further, the reference time Tet is changed according to the opening / closing of the third solenoid valve 73, that is, the presence / absence of communication with the air chamber 83, as described above.

FIG. 7 is a flowchart showing a control procedure by the control unit 40 of the liquid level state detection process executed by the inkjet recording device 1 of the present embodiment. This liquid level state detection process is continuously executed during the operation of the inkjet recording device 1, but may be temporarily stopped when the image recording operation is interrupted. Further, when cleaning of the head or the like is performed, it may be temporarily stopped.

When the liquid level state detection process is started, the control unit 40 (CPU 41) closes the first solenoid valve 71 (usually remains in the closed state) (step S101). The control unit 40 opens the second solenoid valve 72 (step S102).

The control unit 40 determines whether or not there is a recording operation, that is, whether or not the recording operation is in progress or immediately before the recording operation is started in response to the instruction of the recording operation (step S103). When it is determined that the recording operation is in progress (“YES” in step S103), the control unit 40 opens the third solenoid valve 73 (step S114). Then, the process of the control unit 40 shifts to step S105. When it is determined that the recording operation is not in progress (“NO” in step S103), the control unit 40 closes the third solenoid valve 73 (step S104). Then, the process of the control unit 40 shifts to step S105.

When the process shifts to the process of step S105, the control unit 40 starts the operation of the suction pump 82 (step S105). The control unit 40 determines whether or not the air pressure in the ink tank 70 measured by the measurement unit 64 is less than the lower limit value PL (step S106). If it is determined that the value is not less than the lower limit PL (“NO” in step S106), the control unit 40 repeats the process of step S106. If the atmospheric pressure does not fall below the lower limit PL for a long period of time, a larger abnormality is expected due to a failure of the first solenoid valve 71, etc., so the operation is stopped, a predetermined notification operation is performed, and processing is performed. You may cancel.

When it is determined that the atmospheric pressure is less than the lower limit value PL (“YES” in step S106), the control unit 40 stops the operation of the suction pump 82 (step S107). At this time, the control unit 40 starts counting the elapsed time. The control unit 40 determines whether or not the atmospheric pressure of the ink tank 70 exceeds the upper limit value PH (step S108). If the upper limit value PH is not exceeded (“NO” in step S108), the control unit 40 repeats the process of step S108.

When it is determined that the atmospheric pressure exceeds the upper limit value PH (“YES” in step S106), the control unit 40 determines whether the stop time of the suction pump 82 up to this timing is less than the reference time Tet (“YES”). Step S109). If it is determined that the time is not less than the reference time Tet (or more than the reference time Tet), the process returns to step S103.

When it is determined that the stop time of the suction pump 82 is less than the reference time Tet (“YES” in step S109), the control unit 40 determines that the liquid level (meniscus) of the nozzle N is abnormal (“YES”). (Abnormality determination) is performed, various operations related to ink ejection and the like such as an image recording operation and a recording medium transfer operation are stopped, and a predetermined notification operation is performed (step S110). The control unit 40 ends the liquid level state detection process.

As described above, the inkjet recording device 1 of the present embodiment has an operation in which the recording head 231 having the nozzle N for ejecting ink, the ink tank 70 communicating with the nozzle N, and the atmospheric pressure in the ink tank 70 are negative pressures. The suction pump 82 and the control unit 40 are provided. As a discriminating unit, the control unit 40 discriminates whether or not there is an abnormality in the liquid level of the ink in the nozzle N based on the change characteristic of the atmospheric pressure. If there is an abnormality in the ink liquid level in the nozzle N (the meniscus is torn), air enters from the torn part and flows into the ink tank 70 in a negative pressure state, and the ink tank is faster than usual. The pressure inside the 70 rises, or the pressure drop during the operation of the suction pump 82 is delayed. Since the suction pump 82 is operating intermittently to maintain the negative pressure, the inkjet recording device 1 can perform an image reading operation or the like after the recording operation by examining the change characteristic of the atmospheric pressure in this operation cycle. Even if it is not, the abnormality of the liquid level of the ink can be detected efficiently and quickly. In this way, by promptly detecting the abnormality before the recording operation and during the recording operation, it is possible to promptly perform the recovery process before the abnormality worsens, and it is easier to return to the proper image recording operation. be able to.

In addition, the control unit 40, as a discrimination unit, determines the presence or absence of an abnormality according to the rate of change in atmospheric pressure. As described above, since the intrusion of air from the ink liquid surface affects the change in the negative pressure in the ink tank 70, it is possible to determine the abnormality by obtaining the change rate of the atmospheric pressure under a predetermined condition. Since the atmospheric pressure information itself is originally configured to maintain the negative pressure, it is possible to easily detect an abnormality without adding a special configuration.

Further, the control unit 40 starts the decompression operation by the suction pump 82 when the atmospheric pressure is larger than the upper limit value PH, and stops the decompression operation when the atmospheric pressure is less than the lower limit value PL smaller than the upper limit value PH, and serves as a discriminating unit. When the elapsed time from the stop to the start is shorter than the reference time Tet, it is determined that there is an abnormality.
In this way, when the suction pump 82 is operated intermittently between the upper limit value PH and the lower limit value PL of the atmospheric pressure, the increase time of the atmospheric pressure due to the intrusion of air is the decrease time of the atmospheric pressure due to the suction of the suction pump 82. Since it is easier to measure than, the difference from the reference time Tet can be easily discriminated, and the arithmetic processing is also easy.

Further, the suction pump 82 has a fan that sucks air from the ink tank 70. The inside of the ink tank 70 need only be maintained at a negative pressure, and even when the negative pressure is eliminated and the pressure is increased, the atmosphere only needs to flow in. Therefore, as long as the pressure adjusting unit can perform a suction operation, Good. Then, by using a fan as this suction operation, an appropriate negative pressure can be maintained with a simple configuration.

Further, the inkjet recording device 1 also includes a storage unit 50 that stores the reference time Tet as the reference time information 52. Since the reference time Tet is usually almost unchanged, by holding it in advance in this way, it is not necessary for the user to separately input and set it at startup.

Further, the inkjet recording device 1 includes an air chamber 83 that is connected to the ink tank 70 to store air, and a third solenoid valve 73 that switches whether or not the air chamber 83 is connected. The control unit 40 switches the presence / absence of connection by opening / closing the third solenoid valve 73 according to the operating status of the recording head 231. By connecting the air chamber 83 in this way, the capacity related to the negative pressure can be expanded, so that fluctuations in atmospheric pressure during operation can be suppressed as necessary. On the other hand, by making it possible to disconnect the air chamber 83, it is possible to reduce the capacity related to the negative pressure, shorten the change time of the atmospheric pressure, and detect the abnormality of the ink liquid level more quickly.

Further, the control unit 40 switches the third solenoid valve 73 so that the air chamber 83 is not connected when the recording head 231 is not performing the ink ejection operation. That is, since it is preferable to reduce the fluctuation of the negative pressure during the ink ejection operation, it is preferable to connect the air chamber 83, but in other cases, the ink liquid level abnormality can be switched to detectable more quickly. Can be done.

Further, in the abnormality detection method of the present embodiment, a recording head 231 having a nozzle N for ejecting ink, an ink tank 70 communicating with the nozzle N, and a suction pump that operates with the air pressure in the ink tank 70 as a negative pressure. 82 is a method for detecting an abnormality in the liquid level of ink in the nozzle N of the inkjet recording apparatus 1 including the above, and a step of determining the presence or absence of an abnormality in the liquid level in the nozzle N based on the change characteristic of the atmospheric pressure in the ink tank 70. ,including.
As a result, it is possible to efficiently and quickly detect an abnormality in the liquid level of the ink. By promptly detecting the abnormality before the recording operation and during the recording operation in this way, it is possible to quickly perform the recovery process before the abnormality worsens, and it is easier to return to the proper image recording operation. Can be done.

The present invention is not limited to the above embodiment, and various modifications can be made.
For example, in the above embodiment, the abnormality of the ink liquid level is determined based on the time from when the suction pump 82 is turned off to when it is turned on, but the time from on to off may be used. Also, from on to off and from off to on, the shortening / extension of the elapsed time depending on the presence or absence of an abnormality has the opposite characteristic, but since the time from off to on is longer, one such as on to on, off to off, etc. Abnormality can also be determined by measuring the time of the cycle.

Further, for example, the abnormality can be determined by comparing the increase width of the atmospheric pressure within a predetermined time with the reference width during the period from the off to the on of the suction pump 82.

Further, if it is not necessary to acquire the atmospheric pressure value as described above, even if the measuring unit 64 simply detects only the magnitude relationship between the upper limit value PH and the lower limit value PL and outputs the detection signal to the control unit 40. Good. Further, in this case, the control signal may be output to the control unit 40 only at the timing when the magnitude is reversed, and the control unit 40 turns on / on the operation of the suction pump 82 according to the control signal. The process of switching off may be started, and the process may be terminated after the switching.

Further, since it is only necessary to acquire pressure information, the measuring unit 64 may be an external device or module that does not belong to the inkjet recording device 1, and a signal may be acquired from the external device via the communication unit 61. ..

Further, in the above embodiment, the suction pump 82 is used to maintain the negative pressure, but the present invention is not limited to this as long as the negative pressure can be continuously maintained.

Further, the reference time Tet may be input and set by the user each time, or may be updated at appropriate intervals. The value at the time of update may be input by the user, or is set to a constant multiple, for example, 1/3 times, based on the average measurement time from off to on of the suction pump 82 during normal operation. You may. Further, the constant may be appropriately adjusted and set so that the measurement time when an abnormality is actually detected is included.

Further, in the above embodiment, the air chamber 83 is provided, and the air chamber 83 is connected or disconnected by the third solenoid valve 73 depending on the presence or absence of the recording operation, but the air chamber 83 is always connected. Alternatively, the air chamber 83 may not be provided.

Further, the presence / absence of the connection of the air chamber 83 is not switched only depending on the presence / absence of the ink ejection operation, but other operations of the recording head 231 such as a pressure fluctuation that does not eject ink or a maintenance state of the recording head 231. It may be switched according to the above.

Further, in the above embodiment, one recording head 231 is attached to the ink tank 70 to supply ink individually, but a plurality of recording heads are attached to the ink tank 70. Ink may be distributed from the ink tank 70 to these plurality of recording heads. In this case, when an abnormality occurs in the liquid level in any of the plurality of recording heads, the negative pressure change characteristic of the ink tank 70 changes.

In addition, the ink is not limited to colored ink, and includes transparent clear ink and the like. The clear ink may be used to form a coating on the surface of the recording medium. Further, in a 3D printer, the ink may be laminated and solidified after ejection to form a three-dimensional structure.

Further, in the above embodiment, the negative pressure of the ink tank 70 that supplies ink to the recording head 231 (nozzle N) has been described as an example, but the ink discharged from the recording head 231 (nozzle N) is collected. Similarly, when a negative pressure is applied to the ink tank, the presence or absence of an abnormality in the liquid level state may be determined based on the pressure change characteristic of the ink tank on the recovery side.

Further, the pressure fluctuation applying method (thermal method may be used) of the recording head and the nozzle arrangement pattern (the number of recording heads is arbitrary, and even if the recording head ejects ink while being scanned against the recording medium). Good), type of ink (regardless of dye, pigment, etc.), shape of recording medium (for example, paper or cloth continuous in the transport direction), configuration of transport system (for example, recording by belt, etc.) The configuration of the inkjet recording apparatus 1 is not limited to the above embodiment, such as (the medium may be conveyed straight in a plane).
In addition, specific details such as the configuration, structure, arrangement, control content, and procedure shown in the above embodiment can be appropriately changed without departing from the spirit of the present invention.

1 Inkjet recording device 10 Media supply unit 11 Media supply tray 12 Supply transport unit 121, 122 Roller 123 Belt 20 Image formation unit 21 Image formation drum 22 Delivery unit 221 Claw portion 222 Delivery drum 23 Head unit 230 Head module 231 Recording head 24 Fixation Unit 25 Delivery unit 251, 252 Roller 253 Belt 254 Delivery roller 28 Head drive unit 29 Fixing drive unit 30 Media discharge unit 31 Media discharge tray 40 Control unit 41 CPU
42 RAM
45 Transport drive unit 50 Storage unit 51 Program 52 Reference time information 61 Communication unit 62 Display unit 63 Operation reception unit 64 Measurement unit 70 Ink tank 701 Supply path 702 Inflow path 703 Discharge flow path 704 Piping 71 First solenoid valve 72 Second solenoid Valve 73 Third solenoid valve 81 Liquid transfer pump 82 Suction pump 83 Air chamber 90 Bus A Air layer M Recording medium N Nozzle PH Upper limit PL Lower limit Tet Reference time

Claims (8)

A recording head with a nozzle that ejects ink,
An ink storage chamber that communicates with the nozzle and
A pressure adjusting unit that operates to make the air pressure in the ink storage chamber negative.
A discriminant unit that determines the presence or absence of an abnormality in the ink liquid level in the nozzle based on the change characteristic of the atmospheric pressure,
An inkjet recording device characterized by comprising. The inkjet recording apparatus according to claim 1, wherein the discrimination unit determines the presence or absence of the abnormality according to the rate of change of the atmospheric pressure. A control unit that controls the operation of the pressure adjusting unit is provided.
The control unit starts the decompression operation by the pressure adjusting unit when the air pressure is larger than the first reference value, and stops the decompression operation when the air pressure is less than the second reference value smaller than the first reference value. Let me
The inkjet recording apparatus according to claim 2, wherein the discrimination unit determines that the abnormality is present when the elapsed time from the stop to the start is shorter than the reference time. The inkjet recording apparatus according to claim 3, wherein the pressure adjusting unit has a fan that sucks air from the ink storage chamber. The inkjet recording apparatus according to claim 3 or 4, further comprising a storage unit that stores the reference time. An air storage chamber connected to the ink storage chamber to store air and
A switching unit that switches the presence or absence of the connection in the air storage chamber, and
With
The inkjet recording device according to any one of claims 3 to 5, wherein the control unit switches the presence or absence of the connection by the switching unit according to the operating state of the recording head. The inkjet recording device according to claim 6, wherein the control unit switches the switching unit so that the connection of the air storage chamber is not made when the recording head is not performing the ink ejection operation. Ink in the nozzle of an inkjet recording device including a recording head having a nozzle for ejecting ink, an ink storage chamber communicating with the nozzle, and a pressure adjusting unit for operating the pressure in the ink storage chamber as a negative pressure. It is a method of detecting abnormalities in the liquid level of
A step of determining the presence or absence of an abnormality in the liquid level in the nozzle based on the change characteristic of the atmospheric pressure.
Anomaly detection method comprising.

Images