JP6828412B2 - Recording unit maintenance method and inkjet recording device - Google Patents

Description

The present invention relates to a method for maintaining a recording unit and an inkjet recording device.

Conventionally, there is an inkjet recording device that ejects ink from a plurality of nozzles and lands it on a recording medium to record an image. In some inkjet recording devices, many nozzles are arranged in accordance with the demand for high speed and high accuracy of image recording. When increasing the number of nozzles in an inkjet recording device, a technique of arranging a plurality of inkjet heads (recording units) in which a predetermined number of nozzles are arranged is widely used.

In this inkjet recording device, it is necessary to eject ink at an appropriate speed and amount from an opening of a nozzle at an appropriate timing. For this purpose, a technique is known in which an appropriate amount of ink is pumped from an ink tank that stores ink to a nozzle or a tank that generates back pressure according to the pressure of ink near the nozzle. (Patent Document 1). Further, at this time, there is a technique of changing the liquid feed amount (liquid feed rate) according to the temperature of the ink to reduce the change in the liquid feed amount according to the viscosity (Patent Document 2).

On the other hand, in an inkjet recording device, if the nozzles or the ink flow path are clogged or air is mixed in, the ink is not ejected properly and the image quality of the recorded image deteriorates. On the other hand, conventionally, ink is circulated by providing a flow path for ejecting ink from a nozzle or returning ink from a recording unit to an ink tank on a regular basis under predetermined conditions and according to a command based on an operation by a user. Maintenance technology is used to flush out thickened ink, mixed foreign matter, air, etc. by letting them flow.

Japanese Unexamined Patent Publication No. 2014-87983 Japanese Unexamined Patent Publication No. 2011-178060

However, when performing maintenance to flush air or foreign matter from the nozzle, it is necessary to apply a pressure appropriate for the flushing operation to the ink. On the other hand, if the ink pressurized at a predetermined pressure is constantly discharged to the outside from the openings of all the nozzles, there is a problem that the amount of ink leaked increases and there is a lot of waste.

An object of the present invention is to provide a recording unit maintenance method and an inkjet recording device capable of effectively performing maintenance of a target recording unit while reducing waste due to unnecessary ink leakage.

In order to achieve the above object, the invention according to claim 1 is
An ink flow path connecting two or more predetermined number of recording units having nozzles for ejecting ink, a liquid feeding unit for feeding ink, the liquid feeding unit and the predetermined number of recording units, and the ink. It is a maintenance method of a recording unit in an inkjet recording apparatus including the predetermined number of switching units for switching whether or not ink can be supplied to each of the predetermined number of recording units in a flow path.
A liquid feed amount setting step in which the amount of liquid to be fed per unit time in which the ink pressure in the selected recording unit of the predetermined number of recording units is maintained within a predetermined reference range for a reference time or longer is defined as the liquid feed amount during pressurization. ,
A liquid feeding target switching step for switching whether or not ink can be supplied by the predetermined number of switching units depending on whether or not the predetermined number of recording units are selected.
A boosting step in which the selected recording unit is fed by the liquid feeding unit at a boosting liquid feeding amount defined as a liquid feeding amount per unit time when the ink pressure is boosted within the reference range.
A pressurization maintenance step in which the selected recording unit whose ink pressure is within the reference range in the boosting step is fed by the liquid feeding unit at the time of pressurization over the reference time. Including
The liquid feed amount during pressurization is equal to or greater than the maximum value of the liquid feed amount during pressurization that can be determined in the liquid feed amount setting step, and the liquid feed amount during pressurization determined in the liquid feed amount setting step. It is characterized by being set to a fixed value in advance regardless of the value .

The invention of claim 2, in the maintenance method of the recording unit according to claim 1 Symbol placement,
The liquid feed amount setting step is characterized in that the liquid feed amount at the time of pressurization is determined based on the number of the selected recording units.

Further, the invention according to claim 3 is the method for maintaining the recording unit according to claim 1 or 2 .
When the number of the recording units set as the target of liquid transfer is larger than the predetermined upper limit number, the set recording units are each divided into a plurality of groups equal to or less than the upper limit number, and the plurality of times are selected. It is characterized by including a step of selecting a liquid to be sent.

The invention according to claim 4 is the method for maintaining the recording unit according to any one of claims 1 to 3 .
The liquid feeding amount setting step is characterized in that the liquid feeding amount at the time of pressurization is determined based on the information related to the viscosity of the ink to be fed.

The invention according to claim 5 is the method for maintaining the recording unit according to any one of claims 1 to 4 .
The liquid feeding amount setting step is characterized in that the liquid feeding amount at the time of pressurization is determined based on the temperature of the ink to be fed.

The invention according to claim 6 is the method for maintaining the recording unit according to any one of claims 1 to 5 .
The pressurization maintenance step is characterized in that it is started based on the measured value of the pressure sensor that measures the ink pressure.

Further, the invention according to claim 7
Two or more predetermined number of recording units having nozzles for ejecting ink, and
The liquid feeding part that feeds ink and
An ink flow path connecting the liquid feeding unit and the predetermined number of recording units,
The predetermined number of switching units for switching whether or not ink can be supplied to each of the predetermined number of recording units in the ink flow path,
A control unit that controls the amount of liquid sent by the liquid feeding unit per unit time,
With
The control unit
The amount of liquid to be fed per unit time in which the ink pressure in the selected recording unit of the predetermined number of recording units is maintained within the predetermined reference range for the reference time or longer is defined as the amount of liquid to be fed during pressurization.
Whether or not ink can be supplied by the predetermined number of switching units is switched according to whether or not the predetermined number of recording units are selected.
The selected recording unit is fed by the liquid feeding unit at a pressure feeding amount determined as a liquid feeding amount per unit time when the ink pressure is increased within the reference range.
The selected recording unit whose ink pressure is within the reference range is fed by the liquid feeding unit at the pressurizing liquid feeding amount over the reference time.
The feature is that the pressure-pressing liquid feed amount is equal to or more than the maximum value defined as the pressurization liquid feed amount, and is predetermined to a constant value regardless of the pressurization liquid feed amount. It is an inkjet recording device.

According to the present invention, there is an effect that maintenance of the target recording unit can be effectively performed while reducing waste due to leakage of unnecessary ink in the inkjet recording apparatus.

It is an overall perspective view of the inkjet recording apparatus of embodiment of this invention. It is a figure explaining the structure which concerns on the ink flow path in an inkjet recording apparatus. It is a block diagram which shows the functional structure of an inkjet recording apparatus. It is a figure explaining the change of the ink pressure in the inkjet head in the pressure maintenance process. It is a figure explaining the increase of ink pressure in the inkjet head to be pressurized. It is a flowchart which shows the control procedure of the head abnormality detection processing executed by the inkjet recording apparatus of this embodiment. It is a flowchart which shows the control procedure of the individual maintenance process called in the head abnormality detection process. It is a flowchart which shows the modification of the individual maintenance process.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall perspective view of the inkjet recording device 100 according to the embodiment of the present invention.

The inkjet recording device 100 has a plurality of line heads and records an image by a one-pass method, and includes a transport unit 10, an image forming unit 20, an ink storage unit 30, and the like.

The transport unit 10 includes a drive roller 11, a transport motor 12, a transport belt 14, and the like. The transfer motor 12 rotates the drive roller 11 at a predetermined speed. An endless transport belt 14 is wound around the drive roller 11 together with a driven roller (not shown), and the transport belt 14 orbits around the drive roller 11 due to the rotation of the drive roller 11. The recording medium is placed on the transport surface with the outer surface of the transport belt 14 as the transport surface, and the recording medium is transported in the transport direction as the transport belt 14 orbits.

The image forming unit 20 includes a carriage 22, a carriage elevating unit 23, a reading unit 24, and the like, and the combination of the carriage 22 and the carriage elevating unit 23 is provided with a number of sets (8 sets in this case) according to the number of ink colors. Has been done. Each of the carriages 22 extends in a direction intersecting the transport direction (x direction) of the recording medium by the transport unit 10, here, in the width direction (y direction) orthogonal to each other, and is a surface of the transport surface of the recording medium by the transport unit 10. A plurality of inkjet heads 211 (see FIG. 2) are fixed so as to be able to eject ink droplets from the nozzle openings over the entire width of the recording medium arranged above (z direction) to form a line head structure. I'm doing it. The number of nozzles possessed by each inkjet head 211 is appropriately determined according to the recording resolution, the size of the inkjet head 211, and the like. The plurality of carriages 22 are provided at different positions in the transport direction. The carriage 22 is provided so that the distance from the transport surface upward can be changed by the carriage elevating portion 23, and the distance from the transport surface of the inkjet head 211 is also changed as the carriage 22 moves.

The carriage elevating unit 23 changes the distance of the carriage 22 from the transport surface. The carriage elevating portion 23 includes an elevating motor 232, an electromagnetic brake 233, a beam member 234, a support portion 235, and the like.
Two beam members 234 are provided on the upper portion of the transport belt 14 (on the transport surface side of the recording medium) in a direction intersecting the transport direction (here, in the orthogonal direction, that is, in the width direction) substantially in parallel, and the beam member 234 is provided. Support portions 235 are fixed to both ends. An elevating motor 232, an electromagnetic brake 233, and a carriage 22 are attached to the support portion 235.
The carriage 22 is moved up and down in accordance with the operation of the elevating motor 232 and the electromagnetic brake 233 driven based on the control signal from the control unit 40 (see FIG. 3) to determine the position.

The elevating motor 232 moves the carriage 22 at a predetermined elevating speed. As the elevating motor 232, for example, a servo motor or a stepping motor is used.

The electromagnetic brake 233 maintains the fixed state of the carriage 22, and by releasing this fixed state in response to a drive signal, the carriage 22 can be temporarily moved by the elevating motor 232. That is, in a normal state including when the power is turned off, the electromagnetic brake 233 fixes the carriage 22. As the electromagnetic brake 233, for example, a disc brake is used.

The reading unit 24 reads the image recorded on the recording medium. The reading unit 24 includes a line sensor having an image pickup element arranged so that the surface of the recording medium can be imaged over the recordable width of the recording medium. As the line sensor, a well-known one such as a CCD sensor or a CMOS sensor is used. By sequentially imaging in the width direction with the line sensor while transporting the recording medium in the transport direction, it is possible to perform two-dimensional imaging on the recording medium, and the imaging data is sequentially sent to the control unit 40. It is used for inspection of recorded images.

The ink storage unit 30 stores inks of each color used for image recording and supplies them to the inkjet head 211. Here, each configuration of the ink storage unit 30 is arranged in a dedicated rack 35 or the like, and is connected to the image forming unit 20 via a pipe such as a tube.

Next, the configuration related to the ink flow path from the ink storage unit 30 to the image forming unit 20 in the inkjet recording apparatus 100 of the present embodiment will be described.
FIG. 2 is a diagram illustrating a configuration related to an ink flow path in the inkjet recording device 100 of the present embodiment.

The ink storage unit 30 includes a main tank 31, a supply pump 32, and the like.
The main tanks 31 are provided for each ink color and are arranged in the rack 35. The ink in the main tank 31 is sent to the image forming unit 20 by the supply pump 32. The main tank 31 is entirely replaceable, and is formed to be detachably attached to and detachable from the ink flow path to the supply pump 32 regardless of the operating state of the supply pump 32. That is, when the main tank 31 is attached while the supply pump 32 is in the operating state, the ink supply to the image forming unit 20 is immediately restarted.
The supply pump 32 is not particularly limited, but for example, a diaphragm pump, a tube pump, or the like can be used.

In the image forming unit 20, the ink sent from the main tank 31 by the supply pump 32 is stored in the sub tank 251 (storage unit). The sub tank 251 is provided with an ink flow path that returns the ink sent from the sub tank 251 to the sub tank 251 after reaching the inkjet head 211.

The ink flow path from the sub tank 251 to the inkjet head 211 is provided with a flow meter 252, a liquid feed pump 253 (liquid feed unit), a filter 254, a degassing module 255, and a liquid feed common flow path 256. ing. A plurality of individual flow paths 257 are branched from the liquid feed common flow path 256, and ink is sent to the inkjet head 211 through the individual supply valve 258 (switching section) and the damper 259, respectively. Two inkjet heads 211 are connected to each damper 259, and a head unit 21 (recording unit) is configured by two inkjet heads 211 connected to the same damper 259. An ink pressure sensor 256a (pressure sensor) is provided in the liquid feeding common flow path 256, measures the ink hydraulic pressure, and outputs a signal according to the measured value to the control unit 40 (see FIG. 3). The ink pressure sensor is not limited to the liquid feeding common flow path 256, and can measure the ink pressure between the liquid feeding pump 253 and the inkjet head 211 (when the individual supply valve 258 is opened) during the individual maintenance process described later. It suffices if it is provided at a suitable position.

Between the degassing module 255 and the liquid feed common flow path 256, the ink flow path is branched into an intermediate tank flow path 260 and a maintenance flow path 265. The intermediate tank flow path 260 is provided with an intermediate tank flow valve 261, an intermediate tank 262, a common supply valve 263, and the like.
The maintenance flow path 265 is provided with a maintenance flow path flow valve 266.

In the collection flow path 27 from the collection port (outlet) of the inkjet head 211 to the sub tank 251 first, the check valves 271 are connected after the flow paths of the ink discharged from the two inkjet heads 211 branched by the damper 259 merge. It joins the recovery common flow path 272. Then, the ink is returned from the recovery common flow path 272 to the sub tank 251 via the recovery valve 273 and the circulation valve 274. Further, a recovery pump 275 is provided in parallel with the circulation valve 274.

The end of the liquid feed common flow path 256 opposite to the ink inflow side end is directly connected to the downstream side of the recovery valve 273 via the bypass valve 270.
Further, between the liquid feed pump 253 and the filter 254, a check valve is located on the downstream side of the maintenance flow path flow valve 266 of the maintenance flow path 265 and on the downstream side of the intermediate tank flow valve 261 of the intermediate tank flow path 260, respectively. A release flow path for returning ink to the sub tank 251 via 281, 282, and 283 is provided. When the ink sent from the sub tank 251 by the liquid feeding pump 253 does not flow to the inkjet head 211 or cannot flow due to a defect in the filter 254, the degassing module 255, the intermediate tank 262, the liquid feeding common flow path 256, etc. When the ink staying in the middle of the flow path increases and the ink pressure rises, when the pressure of this ink exceeds a predetermined pressure threshold, the check valves 281 to 283 as these relief valves are opened and the ink Can be returned to the sub tank 251.

The capacity of the sub tank 251 is not particularly limited, but here, it is smaller than the capacity of the main tank 31. The sub tank 251 is provided with a liquid amount sensor 251a for detecting the amount of ink stored and a temperature sensor 251b for measuring the temperature of the stored ink.

Here, the liquid amount sensor 251a detects whether or not a standard storage amount of ink for determining whether or not ink is supplied by the supply pump 32 from the main tank 31 to the sub tank 251 is stored. The liquid amount sensor 251a is not limited to this, and may be two sensors that detect the upper limit storage amount and the lower limit storage amount with the standard storage amount in between, or one sensor detects and outputs the storage amount. It may be a thing.

The temperature sensor 251b measures the temperature of the ink and outputs it to the control unit 40 (see FIG. 3). Alternatively, the temperature sensor 251b may measure the wall surface temperature of the sub tank 251 or the like when there is no large difference between the ink temperature and the temperature of the sub tank 251.
In the inkjet recording device 100 of the present embodiment, the sub tank 251 is open to the atmosphere, and the pressure applied to the ink is normally maintained at substantially atmospheric pressure.

The flow meter 252 detects and outputs the amount of liquid sent from the sub tank 251 to the inkjet head 211 side by the liquid feeding pump 253. Here, the measured value of the flow meter 252 is used for status display and holding of history information by the operation display unit 42 (see FIG. 3), and is not used for abnormality detection or the like, but is sent. It may be used for detecting liquid abnormality.

The liquid feed pump 253 delivers (feeds) the ink inside the sub tank 251 to the filter 254 and its downstream side, that is, to the side of the inkjet head 211 at a predetermined liquid feed rate (liquid feed amount per unit time). Here, one liquid feed pump 253 is provided for the sub tank 251 to supply ink to all the inkjet heads 211. Alternatively, ink may be supplied from the sub tank 251 by a plurality of blocks for each predetermined number of inkjet heads 211 (head unit 21) and separate liquid feeding pumps 253. The liquid feeding capacity of the liquid feeding pump 253 can sufficiently supply the maximum amount of ink ejected per unit time by all the inkjet heads 211 accompanying the image recording operation, and further, a predetermined upper limit number (but not particularly limited). Here, it is possible to raise the ink in the head units 21 (16 inkjet heads) (8) to a pressure in a reference range higher than the normal pressure to bring the ink into a pressurized state. As the liquid feed pump 253, the same pump as the supply pump 32 may be used. The liquid feed rate of the liquid feed pump 253 can be changed according to the drive voltage input from the DAC 253a to the liquid feed pump 253 based on the control signal using the input from the predetermined power supply voltage Vcc, and the control unit 40 ( This drive voltage is controlled based on the control signal (see FIG. 3).

The filter 254 removes foreign substances such as dust and dirt, debris, and large air bubbles in the ink. As described above, the sub tank 251 is open to the atmosphere, and these foreign substances, impurities and air bubbles may be mixed. Therefore, the filter 254 prevents them from being sent to the inkjet head 211. It should be noted that the filter 254 and the like are likely to have an area where air remains due to the structure in a normal ink feeding state.

The degassing module 255 removes air (gas) contained in the ink. As the degassing module 255, for example, a structure is used in which the air in the ink is selectively sucked toward the vacuum region side by bringing the ink and the vacuum region into contact with each other through the degassing film. The degassing film can have, for example, a large number of hollow fine thread structures having a vacuum inside in order to efficiently increase the contact area with the ink and make the contact with the ink more evenly.
Here, the air on the vacuum region side of the degassing module 255 is sucked by the vacuum pump 293. The vacuum region referred to here does not necessarily have to be an ultra-high vacuum, and a predetermined atmospheric pressure sufficiently lower than the atmospheric pressure is set in advance. The pressure sensor 294 measures the air pressure on the vacuum region side, and the operation of the vacuum pump 293 is controlled according to the measured value of the pressure sensor 294.

The vacuum region side of the degassing module 255 is connected to the chamber 292 via a check valve 291. Ink that slightly permeates the degassing film or leaks to the vacuum region side at once when the degassing film is torn flows into the bottom of the chamber 292 and is stored. By detecting the amount of ink accumulated in the bottom of the chamber 292 by the liquid amount sensor 292a, it is determined whether or not an abnormal amount has leaked, and when an abnormality is detected, the operation of the vacuum pump 293 and each part is stopped, or the vacuum region Is communicated with the atmosphere. In this way, the chamber 292 is used as a trap for the leaked ink, and by preventing the leaked ink from reaching the vacuum pump 293, failure or damage of the vacuum pump 293 is prevented.

The liquid amount sensor 292a includes an actuator that directly measures the amount of liquid, a member that measures the weight change of the chamber 292, and a member that changes according to the weight change, for example, an actuator that deforms by a load according to the weight of the chamber 292. A signal that is optically, electrically, or magnetically measured in response to the deformation can be used.

The suction unit 29 including the chamber 292, the liquid amount sensor 292a, the pressure sensor 294, and the vacuum pump 293 is commonly provided for the degassing module 255 in the ink flow path provided for each color of ink. , The structure is such that the check valve 291 merges downstream (on the side of the chamber 292). That is, when ink of a certain color leaks from the degassing module 255, the check valve 291 causes the ink of the certain color to flow into the vacuum region side of the degassing module 255 of the ink flow path related to the ink of another color. Is prevented.

The individual supply valve 258 can supply ink from the liquid feed common flow path 256 to the individual flow paths 257 communicating with a predetermined number (two in this case) of the inkjet heads 211 from the liquid feed common flow path 256, that is, each The ink flow state and the non-flow state are switched between the individual flow path 257 and the head unit 21 (inkjet head 211). While all of these individual supply valves 258 are opened during normal image recording operation, these are individual when the ink in the intermediate tank 262 and the liquid feed common flow path 256 is returned to the sub tank 251 without being discharged to the outside and collected. The supply valve 258 is closed and the bypass valve 270 is opened. Further, when ink is selectively supplied to the part of the head unit 21 for inspection, cleaning, maintenance, etc. of the part of the inkjet head 211, the individual flow path 257 communicating with the part of the head unit 21 Only the individual supply valve 258 provided in the above is opened, and the other individual supply valves 258 are closed.
Here, as an example, four individual flow paths 257, four individual supply valves 258, and four head units 21 are shown (eight inkjet heads 211), but this number can be used to supply ink to the inkjet head 211. A number corresponding to each other (usually a plurality of line heads; a predetermined number of 2 or more) can be appropriately set within a range that does not cause a problem in the ejection operation from the nozzle.

Next, the functional configuration of the inkjet recording device 100 of the present embodiment will be described.
FIG. 3 is a block diagram showing a functional configuration of the inkjet recording device 100.
The inkjet recording device 100 includes the above-mentioned supply pump 32, liquid feed pump 253, recovery pump 275, vacuum pump 293, liquid level sensor 251a, temperature sensor 251b, DAC253a, ink pressure sensor 256a, pressure sensor 294, liquid level sensor 292a, and the like. In addition to the intermediate tank flow valve 261, maintenance flow path flow valve 266, common supply valve 263, individual supply valve 258, recovery valve 273, circulation valve 274, electromagnetic brake 233, elevating motor 232, and reading unit 24, the control unit 40 A communication unit 41, an operation display unit 42, a transfer motor 12, a head drive unit 221, a motor driver 231 and a notification operation unit 43 are provided.

The control unit 40 controls the overall operation of the inkjet recording device 100 and controls the operation of each unit. The control unit 40 includes a CPU 401 (Central Processing Unit), a RAM 402 (Random Access Memory), a ROM 403 (Read Only Memory), a memory 404, and the like.

The CPU 401 performs various arithmetic processes to control the transfer of the recording medium, the supply of ink, the ejection of ink, the maintenance operation, and the like in the inkjet recording device 100. Further, the CPU 401 performs various processes related to image recording based on the image data, the status signal of each part, the clock signal, and the like according to the program read from the ROM 403.

The RAM 402 provides the CPU 401 with a working memory space and stores temporary data.
The ROM 403 stores a control program, initial setting data, and the like. The control program includes a program related to ink supply control and maintenance operation of the inkjet recording device 100.

Further, the ROM 403 includes a non-volatile memory that can be overwritten and updated, and includes the measured value of the temperature sensor 251b, the liquid feeding speed of the liquid feeding pump 253 during pressurization maintenance, and (a feeding amount that can be determined as the liquid feeding amount during pressurization). The liquid feed adjustment table 403a in which the liquid speed) is associated with the preset ink type and the number of the inkjet heads 211 selected as the target of the pressurization maintenance described later is stored. The memory 404 includes a RAM for temporarily storing image data to be recorded.

The head drive unit 221 generates and outputs a drive voltage signal that deforms the pressure chamber (piezoelectric element) in order to properly eject ink from the nozzles in each of the inkjet heads 211. The head drive unit 221 selects a voltage waveform pattern stored in advance based on the control signal from the control unit 40 to generate a power-amplified drive voltage signal, and each of the head drive units 221 responds to the image data input from the memory 404. Whether or not the drive voltage signal can be output to the piezoelectric element is switched.
The wiring related to the head drive unit 221 is formed together with the ink flow path in the inkjet head 211, and is partially formed separately.

The motor driver 231 outputs a drive signal to the electromagnetic brake 233 and the elevating motor 232 in response to the control signal from the control unit 40, loosens the electromagnetic brake 233 and operates the elevating motor 232 to move the carriage to a desired position. Alternatively, the elevating motor 232 is stopped and the carriage is fixed by the electromagnetic brake 233.

The communication unit 41 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 board and a LAN card. The communication unit 41 acquires image data to be recorded and setting data (job data) related to image recording from an external device based on the control of the control unit 40, and also transmits status information and the like to the external device. Can be done.

The operation display unit 42 displays the status of the inkjet recording device 100, the operation menu, and the like in response to the control signal from the control unit 40, and receives the user's operation and outputs the operation to the control unit 40. The operation display unit 42 includes, for example, a liquid crystal display unit in which a touch sensor as an operation receiving means is provided so as to overlap with a display screen as a display means. The control unit 40 displays the status and various menus for receiving commands by the touch sensor on the liquid crystal display unit, and displays the contents and position information of the displayed menu and the user's touch operation detected by the touch sensor. A control operation is performed in which each part of the inkjet recording apparatus 100 performs the corresponding processing.

The notification operation unit 43 performs a predetermined notification operation in response to the control signal of the control unit 40. Examples of the configuration for performing the notification operation include an LED lamp that emits light of a predetermined color and / or a beep sound generating unit that generates a beep sound.
In addition to these, the inkjet recording device 100 may be provided with a mounting abnormality detection sensor or the like that detects that the supplied recording medium is not normally mounted on the transport surface.

The bus 49 is a path for electrically connecting each of the above configurations to exchange signals.

Next, the maintenance operation of the inkjet head 211 in the inkjet recording device 100 of the present embodiment will be described.
In the inkjet recording device 100 of the present embodiment, when a problem occurs in the image quality of the formed image by the image forming unit 20, or when a problematic nozzle is detected by a normal nozzle ejection inspection, for example, the nozzle of the inkjet head 211 Ink in the inkjet head 211 with respect to the inkjet head 211 in which image quality deteriorates or nozzles with poor ejection occur when the ink is clogged or air bubbles are mixed in and the ink cannot be ejected normally. Pressurized maintenance process (maintenance method) is performed to flush out air bubbles, etc. by sending the liquid so that the ink is pressurized.

At this time, in the inkjet head 211, the ink pressure required to properly push out the clogging and air bubbles and the duration thereof are determined. If the ink pressure is lower than these or the duration is insufficient, clogging or air bubbles are likely to remain, while if the ink pressure is higher or the duration is longer than these, the effect of pushing out clogging or air bubbles is effective. It leads to an increase in the amount of ink leaking from the nozzle opening and an extension of the required time without changing.

As described above, the pressurization maintenance process is performed by selecting the inkjet head 211 having the nozzle to be pressurized. That is, the number (selected number) of the selected inkjet heads 211 is not limited to a fixed number, and the individual supply valve 258 to the head unit 21 including the inkjet heads 211 to be pressurized is opened to the other head units 21. The individual supply valve 258 and the recovery valve 273 of the above are closed. The difference between the liquid feed amount by the liquid feed pump 253 and the leakage amount from the nozzle of the inkjet head 211 related to the head unit 21 in which the individual supply valve 258 is opened in this state is an increase in the ink amount in the ink flow path and the inkjet head 211. Minutes, that is, an increase in pressure.

The amount of leakage from the nozzle (outflow ink rate) is mainly based on the difference between the ink pressure in the inkjet head 211 minus the effect of pressure loss due to the conduit resistance in the nozzle and the external pressure (atmospheric pressure). It is decided. That is, the higher the ink pressure, the larger the leakage amount, and the smaller the pipeline resistance, the larger the leakage amount. Therefore, when the liquid feeding speed (the amount of ink flowing into the inkjet head 211) is fixed, the ink pressure gradually rises while the ink pressure in the inkjet head 211 is low and the amount of leakage is small, but the ink When the pressure rises to a predetermined level, the amount of ink leaking from the inkjet head 211 finally balances with the amount of ink inflow, and the ink pressure does not rise (saturates). When the same pressure is applied to the pressurizing target inkjet head 211, the amount of leakage increases in proportion to the number of the pressurizing target inkjet heads 211, that is, the number of leaking nozzle openings. Therefore, if the number of the inkjet heads 211 to be pressurized is increased with respect to the fixed liquid feeding rate, the saturation value of the ink pressure decreases.

Therefore, in the inkjet recording device 100 of the present embodiment, the saturation value of the ink pressure is set to the above-mentioned reference range (lower limit value PL or higher) according to the number of the inkjet heads 211 to be pressurized (that is, the number of head units 21). By changing the liquid feed rate (pressurized liquid feed rate; the amount of liquid feed during pressurization) so as to be (value PH or less), the ink pressure is stably maintained within the reference range. The correspondence between the number of head units 21 to be pressurized, the combination of ink type and ink temperature, and the pressurized liquid feed rate (that is, the drive voltage output from the DAC 253a to the liquid feed pump 253) is the liquid feed adjustment table 403a. Read from. When the change according to the ink type and the ink temperature is small, these need not be taken into consideration.

FIG. 4 is a diagram illustrating a change in ink pressure in the inkjet head 211 during the pressure maintenance process.

In the pressurization maintenance process, the pressurization state at the ink pressure (lower limit value PL or more and upper limit value PH or less) in an appropriate range (predetermined reference range) in each nozzle (inverter head 211, head unit 21) is ΔTK (predetermined time ΔTK). Ink whose ink pressure saturation value is within the reference range (or slightly exceeds the upper limit PH) for the selected n inkjet heads 211 so as to be continued (maintained) for more than the reference time). Pressurized liquid feed rate is set. As a result, the ink pressure at the initial pressure P0 rises to within the reference range while gradually reducing the pressure rise rate at the boosting time ΔTRn from the timing t0 of the start of liquid feeding to the timing t1n, and the ink is small within the reference range. It is maintained for a predetermined time ΔTK until the timing t2n due to the change in pressure.

At this time, as described above, the presence of an air layer or the like on the filter 254 or the like causes the amount of ink required to increase the pressure of the inkjet head 211 to be pressurized. Further, when the volume of the liquid feeding common flow path 256 or the like is large in the inkjet head 211 and the individual flow path 257 as compared with the volume, the amount of ink required to increase the ink pressure in the inkjet head 211 by a predetermined width is subject to pressurization. It increases regardless of the number of inkjet heads 211. Therefore, the time required to supply these required ink amounts and raise the ink pressure from the initial pressure P0 to the lower limit value PL becomes longer as the liquid feeding speed becomes smaller.

FIG. 5 is a chart illustrating an increase in ink pressure in the inkjet head 211 to be pressurized.

As shown in FIG. 5A, when there is one head unit 21 to be pressurized (two inkjet heads 211), the pressure feeding rate is such that the saturation value of the ink pressure is within the reference range. The time required to raise the ink pressure in the inkjet head 211 within the reference range (pressurization time ΔTR1) is 25 seconds, and as the number of head units 21 to be pressurized increases one by one, 15 seconds. It becomes shorter to 10 seconds, 7 seconds, and 5 seconds. When the number of head units 21 to be pressurized is 5 or more, the time required for pressurization ΔTRn becomes substantially constant in 5 seconds.

Due to this effect, when ink is fed and pressurized at a pressurizing liquid feeding rate determined according to the number of pressurizing target inkjet heads 211 and the saturation value, the number of inkjet heads 211 to be pressurized at one time. Is less than the number in the example of FIG. 4 (here, n> 1) (when the pressure liquid feeding speed becomes small), for example, when the number of head units 21 to be pressurized is one (n = 1). As shown in FIG. 5B, the time required for boosting ΔTR1 from the initial pressure P0 (timing t0) to the rise in the reference pressure (lower limit PL) (timing t11) of the ink pressure in the pressurizing target inkjet head 211. Is longer than the time required for boosting ΔTRn. The ink leaking from the nozzle during boosting is wasted, that is, the longer the time required for boosting, the greater this waste. Therefore, it is preferable that the time required for boosting is as short as possible.

Therefore, in the inkjet recording device 100 of the present embodiment, the ink liquid feeding speed (boosting liquid feeding speed; the amount of liquid feeding at the time of boosting) during the pressurization of the ink pressure does not depend on the number of the inkjet heads 211 to be pressurized. (I. When the ink pressure reaches the reference range, the pressure is switched to an appropriate pressure feed rate, which is determined according to the number of the inkjet heads 211 to be pressurized.

Normally, the liquid feed pump 253 is sufficient as long as it can supply the amount of ink consumed in the ink ejection operation. Therefore, from the viewpoint of cost and size, it is not possible to provide a liquid feed pump 253 capable of feeding ink at a liquid feed rate corresponding to the case where the pressurization maintenance process is performed for all the inkjet heads 211 at once. .. As a result, when the number of inkjet heads 211 to be pressurized increases (here, when the number exceeds the upper limit of eight as described above), the pressurized liquid feed required to set the saturation value of the ink pressure within the reference range. The speed may exceed the maximum liquid feeding capacity of the liquid feeding pump 253. In such a case, the inkjet head 211 (head unit 21) to be pressurized is divided into a plurality of groups (sets), the head units 21 of each group are separately selected, and the divided sets of the plurality of sets are selected. Perform pressurization maintenance processing as many times as the number. If the number of groups to be divided is larger than necessary, the pressurization maintenance time will be longer, so the number of groups should be the minimum required to keep the number of head units 21 in each group below the upper limit. Will be done.

FIG. 6 is a flowchart showing a control procedure by the control unit 40 of the head abnormality detection process executed by the inkjet recording device 100 of the present embodiment.

This head abnormality detection process is performed at the initial operation after the power supply of the inkjet recording device 100 is turned on, periodically every time an image is recorded on a predetermined number of recording media P, and the operation display unit 42 by the user. It is started when an execution command is received in response to a predetermined input operation to.

When the head abnormality detection process is started, the control unit 40 outputs a control signal to the head drive unit 221 and of each nozzle at a predetermined position of the recording medium P to be conveyed, for example, in the margin of a normal recording target image. A test image for detecting a discharge abnormality is formed (step S401). The control unit 40 operates the reading unit 24 to capture a test image formed on the recording medium (step S402). The control unit 40 detects an abnormality based on the captured data of the acquired test image, and identifies the inkjet head 211 in which the abnormality has occurred (step S403).

The control unit 40 determines whether or not an abnormality has been detected (step S404), and if it is determined that no abnormality has been detected (“NO” in step S404), ends the head abnormality detection process. If it is determined that an abnormality has been detected (“YES” in step S404), the control unit 40 performs an individual maintenance process from all the inkjet heads 211 selected as targets for the individual maintenance process. The number of the inkjet heads 211 to be generated is determined (selected) by the above-mentioned upper limit number or less (step S405). The control unit 40 performs the individual maintenance process on the head unit 21 including the inkjet head 211 determined by calling the individual maintenance process (step S406). The control unit 40 determines whether or not the individual maintenance processing of all the inkjet heads 211 to be the target of the individual maintenance processing has been completed (step S407). If it is determined that the process has not been completed (“NO” in step S407), the process of the control unit 40 returns to step S405, and the remaining inkjet head 211 is determined (selected) as a target. If it is determined that the process has ended (“YES” in step S407), the control unit 40 ends the head abnormality detection process.
Of these processes, the process of steps S405 and S407 constitutes the liquid feed target selection step.

The abnormality detection from the test image may be visually performed by the user. In this case, the process of step S402 and the process of detecting an abnormality by the control unit 40 in the process of step S403 are omitted, and the inkjet head 211 in which an abnormality occurs according to the information of the inkjet head 211 input to the operation display unit 42 by the user is omitted. To identify. Alternatively, the control unit 40 displays the inkjet head 211 determined to be the target of the individual maintenance process on the operation display unit 42, causes the user to input an operation such as approval, addition, or deletion, and finally performs individual maintenance. The target of processing may be determined (set).

Further, after the processing in step S406 is completed, the control unit 40 returns the processing to step S401, detects again whether the abnormality has been resolved, and repeats the individual maintenance process for the head unit 21 including the inkjet head 211 in which the abnormality is not resolved. It may be done by.

FIG. 7 is a flowchart showing a control procedure by the control unit 40 of the individual maintenance process called in the head abnormality detection process.

When the individual maintenance process is called, the control unit 40 closes the common supply valve 263, closes the intermediate tank flow valve 261 and opens the maintenance flow path flow valve 266 (step S101). The control unit 40 closes the individual supply valve 258 provided in the individual flow path 257 of the head unit 21 that is excluded (not selected) according to whether or not the determined individual maintenance target is selected (step). S102; liquid feed target switching step).

The control unit 40 determines the pressurized liquid feed rate of the ink according to the number of head units 21 to be individually maintained with reference to the liquid feed adjustment table 403a (step S103; liquid feed amount setting step). The control unit 40 outputs a control signal to the DAC 253a to output a drive voltage corresponding to a predetermined step-up liquid feed rate, and causes the liquid feed pump 253 to perform a liquid feed operation at the step-up liquid feed rate (the step-up liquid feed rate). Step S104).

The control unit 40 acquires the ink pressure measured by the ink pressure sensor 256a and determines whether or not the ink pressure is equal to or higher than the lower limit value PL (step S105). If it is determined that the value is not equal to or higher than the lower limit PL (“NO” in step S105), the control unit 40 repeats the process of step S105. The execution interval of the process in step S105 may be appropriately determined within a range in which the detection of the ink pressure equal to or higher than the lower limit value PL is not significantly delayed (for example, 0.5 seconds or longer).

When it is determined that the ink pressure is equal to or higher than the lower limit PL (“YES” in step S105), the control unit 40 outputs a control signal to the DAC253a and responds to the determined pressurized liquid feeding speed. The driving voltage is changed, and the liquid feeding operation by the liquid feeding pump 253 is performed at the pressurized liquid feeding speed (step S106). That is, the control unit 40 starts the pressurizing operation based on the measured value of the ink pressure sensor 256a. In addition, the control unit 40 counts the elapsed time from the determined timing.

The control unit 40 determines whether or not a predetermined time ΔTK or more has elapsed from the timing when the ink pressure equal to or higher than the lower limit value PL is detected (step S107). This predetermined time ΔTK is predetermined as a time normally required for discharging air bubbles and clogging from the ink flow path and nozzles of each inkjet head 211, for example, 5 seconds, but can be changed. Is also good.

When it is determined that the predetermined time ΔTK or more has not elapsed from the timing when the ink pressure equal to or higher than the lower limit value PL is detected (“NO” in step S107), the control unit 40 repeats the process of step S106. The execution interval of the process in step S107 can be appropriately determined within a range sufficiently shorter than the above-mentioned predetermined time ΔTK (for example, 1/10 or less of the predetermined time ΔTK). When it is determined that the predetermined time ΔTK or more has elapsed (that is, the timing at which the predetermined time ΔTK has elapsed (elapsed timing) due to an error of about the above-mentioned execution interval) (“YES” in step S107), the control unit Reference numeral 40 denotes a control signal output to the DAC 253a to stop the liquid feeding operation by the liquid feeding pump 253 and end the liquid feeding (step S108).

The control unit 40 opens the bypass valve 270 and the circulation valve 274 (step S109). The control unit 40 opens the intermediate tank flow valve 261 and the common supply valve 263, and closes the maintenance flow path flow valve 266 (step S110). The control unit 40 closes all the individual supply valves 258, and then operates the recovery pump 275 to suck the ink in the liquid feed common flow path 256 and the like, and adjusts the amount of ink inside the intermediate tank 262 to an appropriate amount. (Step S111).

The control unit 40 closes the bypass valve 270 and the circulation valve 274, and opens all the individual supply valves 258 (step S112). Then, the control unit 40 ends the individual maintenance process and returns the process to the head abnormality detection process.
The processing of steps S104 and S105 constitutes a boosting step, and the processing of steps S106 and S107 constitutes a pressurizing maintenance step.

In the above embodiment, the difference between the elapsed time until the pressure reaches the lower limit PL or more in the discrimination process of step S105 and the elapsed time originally assumed based on the test result or the like, or the pressure becomes the lower limit PL or more. When the situation when the lower limit value PL is lower or the upper limit value PH is exceeded is stored in the non-volatile memory of the ROM 403, and a long-term deviation tendency occurs due to aging or the like. May be used after correcting the liquid feed adjusting table 403a to reflect the deviation.

[Modification example]
Next, a modified example of the individual maintenance process executed by the inkjet recording apparatus 100 will be described.

As mentioned above, the saturation value of the ink pressure depends on the line resistance of the ink. The ink pipeline resistance changes not only with the number of nozzle openings (inkjet heads 211 to be pressurized) but also with the ink material (that is, the type of ink) and the viscosity of the ink. Since the viscosity of the same type of ink changes mainly depending on the temperature of the ink, for example, in the inkjet head 211 that ejects the ink whose viscosity decreases as the temperature of the ink rises, the temperature of the ink is set in advance. When the temperature is higher than the specified reference temperature, the saturation value of the ink pressure decreases, and when the temperature is lower than the reference temperature, the saturation value of the ink pressure increases. In this modified example of the individual maintenance process, the liquid feeding rate is changed according to the ink type and the ink temperature (here, the temperature measured by the temperature sensor 251b; the information related to the viscosity).

FIG. 8 is a flowchart showing a modified example of the individual maintenance process in the inkjet recording apparatus 100 of the above embodiment.
In a modified example of this individual maintenance process, the process of step S121 is added to the above-mentioned individual maintenance process, and the processes of steps S105a and S107a are performed instead of the processes of steps S105 and S107, respectively. The processes other than these are the same, and the same process contents are designated by the same reference numerals and detailed description thereof will be omitted.

Following the process in step S102, the control unit 40 acquires information on the ink type and the ink temperature (step S121). The control unit 40 determines an appropriate pressurizing liquid feeding rate based on the number of head units 21 to be pressurized, the ink type, and the ink temperature with reference to the liquid feeding adjusting table 403a (step S103). Then, the process of the control unit 40 shifts to step S104.

When the liquid feeding operation at the boosted liquid feeding rate is started in the process of step S104, the control unit 40 determines whether or not the preset boosting time ΔTR has elapsed from the start of the liquid feeding (step S105a). ). If it is determined that the process has not elapsed (“NO” in step S105a), the control unit 40 repeats the process of step S105a. If it is determined that the elapse has passed (“YES” in step S105a), the process of the control unit 40 shifts to step S106.

Further, when the process of step S106 is changed to the liquid feeding operation at the pressurized liquid feeding speed, the control unit 40 determines whether or not the predetermined time ΔTK has elapsed from the timing of the speed change (step S107a). If it is determined that the process has not elapsed (“NO” in step S107a), the control unit 40 repeats the process of step S107a. If it is determined that the elapse has passed (“YES” in step S107a), the process of the control unit 40 shifts to step S108.

As described above, in the maintenance method of the recording unit (inkjet head 211) in the inkjet recording device 100 of the present embodiment, two or more predetermined number of head units 21 having nozzles for ejecting ink and feeding ink to feed ink. Ink flow paths (maintenance flow path 265, liquid transfer common flow path 256, individual flow paths 257, etc.) connecting the liquid pump 253, the liquid supply pump 253, and a predetermined number of head units 21 and predetermined ink flow paths. A maintenance method for an inkjet head 211 in an inkjet recording device 100 including the predetermined number of individual supply valves 258 for switching whether or not ink can be supplied to each of the number of head units 21.
The amount of liquid to be fed per unit time (feeding) in which the ink pressure in the selected head unit 21 out of the predetermined number of head units 21 is maintained within a predetermined reference range (lower limit value PL or more and upper limit value PH or less) for a predetermined time ΔTK or more. A liquid feed amount setting step that defines (liquid speed) as a pressurized liquid feed rate, and a liquid feed target switching step that switches whether or not ink can be supplied by a predetermined number of individual supply valves 258 depending on whether or not a predetermined number of head units 21 are selected, are selected. The ink pressure is used as a reference in the step-up step and the step-up step in which the liquid is fed by the liquid feed pump 253 at a boosted liquid feeding speed defined as the liquid feeding speed when the ink pressure is raised within the above-mentioned reference range with respect to the head unit 21. The pressurized liquid feed rate includes a pressurization maintenance step of feeding the selected head unit 21 within the range by the liquid feed pump 253 at a pressurized liquid feed rate for a predetermined time ΔTK. It is larger than the minimum value of the pressurized liquid feeding speed that can be determined in the setting step (that is, the pressurized liquid feeding speed when n = 1), and according to the number n of head units subject to pressure maintenance in the liquid feeding amount setting step. It is a value equal to or higher than the specified pressurized liquid feeding speed.
As a result, even if the number of the inkjet heads 211 (head units 21) subject to individual maintenance differs for each execution of individual maintenance, the ink pressure required for the target inkjet heads 211 each time and the required duration ink Can be sent. On the other hand, even if the number of inkjet heads 211 (head units 21) subject to individual maintenance is small, the time for boosting the ink pressure can be kept short. Therefore, it is possible to maintain an appropriate ink pressure in the target inkjet head 211 for an appropriate duration while reducing waste due to unnecessary ink leakage, thereby effectively adding the head unit 21 (nozzle). Pressure maintenance can be performed.

Further, the boosted liquid feeding rate is predetermined to be equal to or higher than the maximum value that can be determined as the pressurized liquid feeding rate based on the liquid feeding adjustment table 403a.
As a result, ink can be supplied at a higher speed than during pressurization at the time of boosting, except in the situation where the liquid is fed at the maximum speed that can be set as the pressurized liquid feeding speed from the beginning at the time of boosting. The pressure rises and the time required for boosting is reduced. Therefore, in the inkjet recording device 100, the ink pressure can be raised to the saturation value (within the reference range) while reducing the leakage from the nozzle.

Further, the step-up liquid feed rate is predetermined to a constant value regardless of the predetermined pressurized liquid feed rate. As a result, it is not necessary to set the pressurization / boosting speed each time, and it is not necessary to hold the set value in a table or the like in advance. Therefore, the ink pressure can be easily and quickly boosted at an appropriate pressurizing / boosting speed. Can be done.

Further, in the liquid feeding amount setting step, the liquid feeding speed is determined based on the number of selected head units 21. Normally, the structure of the inkjet head 211 and the number of the inkjet heads 211 constituting each head unit 21 are the same. Therefore, if the number of target head units 21 and the liquid feeding speed are associated with each other, it is easily appropriate. It is possible to effectively perform pressurization maintenance by determining the liquid feeding speed.

Further, in the maintenance method of the inkjet head 211 of the present embodiment, when the number of head units 21 set as the target of liquid feeding is larger than the predetermined upper limit number (8), the set head units 21 are used. Includes a liquid delivery target selection step in which each is divided into a plurality of sets of the upper limit or less and the selection is performed a plurality of times.
That is, it is not necessary to equip all the head units 21 with a powerful liquid feed pump 253 that can perform pressurization maintenance at the same time, and by appropriately dividing the pumps 253, it is possible to suppress an increase in manufacturing and product costs. ..

Further, in the liquid feeding amount setting step, the liquid feeding speed is determined based on the information related to the viscosity of the ink to be fed. As described above, since the line resistance of the ink in the nozzle depends on the viscosity, the saturation value of the ink pressure rises and falls from the reference state depending on the viscosity, and the ink is not sufficiently pressurized or the pressure is higher than necessary. As a result, the amount of leakage increases. Therefore, by determining the liquid feeding rate in consideration of the viscosity, stable pressurization maintenance can be performed at a more appropriate pressure.

Further, in the liquid feeding amount setting step, the liquid feeding speed is determined based on the temperature of the ink to be fed.
It takes time and effort to actually measure the above-mentioned viscosity, and a dedicated device is required, which leads to an increase in cost and time. Therefore, the liquid is sent according to the measured value of the temperature which has a large correlation with the normal viscosity. By adjusting the speed, it is possible to easily perform stable pressurization maintenance at an appropriate pressure.

Further, in the pressurization execution step, the timing of changing to the pressurized liquid feed rate, that is, the counting start timing of the predetermined time ΔTK is determined based on the measured value of the ink pressure sensor 256a that measures the ink pressure. That is, it is confirmed that the pressure in the range of the lower limit value PL or more and the upper limit value PH or less is actually applied over the predetermined time ΔTK by switching from the boosting to the pressurization maintenance by actually using the measured value of the ink pressure sensor 256a. Even if the liquid feeding speed of the liquid feeding pump 253 changes slightly from the set value due to uneven operation or aging, and the boosting time ΔTR until the ink pressure reaches the lower limit PL is deviated, the inkjet head 211 is surely used. The ink is pressurized for the required predetermined time ΔTK. Further, since it is possible to detect when the ink pressure does not reach the lower limit value PL, stable pressurization maintenance can be performed more reliably.

Further, in the inkjet recording device 100 of the present embodiment, two or more predetermined number of head units 21 having nozzles for ejecting ink, a liquid feeding pump 253 for feeding ink, a liquid feeding pump 253 and a predetermined number of heads Ink supply to each of the ink flow paths such as the intermediate tank flow path 260, the maintenance flow path 265, the liquid feed common flow path 256, and the individual flow path 257 that connect the unit 21, and a predetermined number of head units 21 in the ink flow path. It is provided with a predetermined number of individual supply valves 258 for switching between availability and a control unit 40 for controlling the amount of liquid to be fed (liquid feeding speed) per unit time by the liquid feeding pump 253. The control unit 40 feeds at pressurization a liquid feeding speed at which the ink pressure in the head unit 21 selected from the predetermined number of head units 21 is maintained at a predetermined time ΔTK or more within a range of the lower limit value PL or more and the upper limit value PH or less. Determined as the amount of liquid. The control unit 40 switches whether or not to supply ink by a predetermined number of individual supply valves 258 depending on whether or not a predetermined number of head units 21 are selected. Then, the control unit 40 determines the pressure-pressing liquid feeding amount per unit time when the ink pressure is increased to the selected head unit 21 within the reference range of the lower limit value PL or more and the upper limit value PH or less. The liquid is fed by the liquid feeding pump 253 at a speed, so that the liquid feeding pump at a pressurized liquid feeding speed to the selected head unit 21 whose ink pressure is within the reference range of the lower limit value PL or more and the upper limit value PH or less. The liquid is sent over a predetermined time ΔTK by 253. The boosted liquid feeding speed at this time is a value larger than the minimum value that can be determined as the pressurized liquid feeding speed based on the liquid feeding adjusting table 403a and equal to or higher than the specified pressurized liquid feeding speed.
By controlling the pressurizing liquid feeding rate during pressure maintenance in this way, the number of inkjet heads 211 (head units 21) to be individually maintained in the inkjet recording device 100 differs each time individual maintenance is performed. Also, the ink can be fed to the target inkjet head 211 so that the required ink pressure is maintained for the required duration each time. On the other hand, by setting the boosted liquid feeding speed higher than the pressurized liquid feeding speed and shortening the boosting time ΔTR, it is unnecessary especially when the number of inkjet heads 211 (head units 21) subject to individual maintenance is small. Reduce the amount of ink leakage. Therefore, it is possible to maintain an appropriate ink pressure in the target inkjet head 211 for an appropriate duration while reducing waste due to unnecessary ink leakage, thereby effectively performing pressurization maintenance of the nozzle. 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, two inkjet heads 211 are paired and one individual supply valve 258 determines whether or not the liquid can be fed together, but the present invention is not limited to this. Individual supply valves 258 may be provided for each of the inkjet heads 211.

Further, in the above embodiment, it is assumed that all the inkjet heads 211 have the same configuration, but it does not exclude the case where the inkjet heads 211 having different numbers and arrangements of the provided nozzles coexist. In this case, the liquid feeding rate is also changed based on the number of nozzles of the selected inkjet head 211.

Further, in the above embodiment, the control unit electromagnetically controls the opening and closing of the individual supply valve 258, but a valve and an opening / closing mechanism that can be opened / closed by a user or an administrator using a hand or an instrument are provided. It may be switched manually.

Further, in the above embodiment, the liquid feeding speed is changed or the liquid feeding operation is performed at the timing when the boosting time ΔTR elapses from the start of the liquid feeding and the timing when the predetermined time ΔTK elapses after the pressure equal to or higher than the lower limit PL is detected. However, when the control is not actually performed based on the measured value of the ink pressure as in the modified example, the actual operation of the liquid feed pump 253 is taken into consideration such as unevenness and secular change. The duration may be set slightly longer than the value obtained in advance by inspection or the like. However, as described above, if it is too long, the power consumption required for the operation will increase and the amount of ink leakage will only increase. Therefore, the operation accuracy of the liquid feed pump 253 (usually assumed unevenness and deterioration) will be improved. It is desirable not to take too much room.

Further, in the above embodiment, the step-up liquid feed rate is set to be equal to the pressurized liquid feed rate when the number of selections is 8, but the present invention is not limited to this. Assuming that the boosted liquid feed rate is equal to or higher than the specified pressurized liquid feed rate, the number of selections is 4 or less, that is, the number of times the required boosting time changes according to the number of selections (here, the required boosting time of seconds or less). Is not taken into consideration), especially when the number of selections for which the time required for boosting is significantly long is 1 (at least when the minimum value of the liquid feed amount during pressurization that can be determined based on the liquid feed adjustment table 403a). , A speed larger than the pressurized liquid feeding speed according to the number of selections may be set as the pressurized liquid feeding speed. For example, the pressurized liquid feeding speed may be set when the number of selections is always 5. Alternatively, as the step-up liquid feed rate, when the number of selections is 4 or less, the pressurized liquid feed rate is set when the number of selections is 5, and when the number of selections is 5 or more, the step-up liquid feed rate and the pressurized liquid feed rate are set. May be equal. When the number of selections is 7 or less, the pressurized liquid feeding speed when the number of selections is 1 is set as the boosted liquid feeding speed, and when the number of selections is 8, the pressurized liquid feeding speed and the pressurized liquid feeding speed are set. May be equal.

That is, in the inkjet recording device 100, the step-up liquid feeding speed may be a fixed value predetermined as a fixed value, or may be a value determined according to the predetermined pressurized liquid feeding speed. In the former case, for example, a constant value may be incorporated in the processing program in advance, and in the latter case, for example, in the liquid feed adjustment table 403a, the boosted liquid feed rate and the pressurized liquid feed rate are set. Both may be determined with reference to this.

Further, in the above embodiment, only one liquid feeding pump 253 and the inkjet head 211 to which ink is supplied by the liquid feeding pump 253 have been described, but the inkjet in which the liquid is fed by different liquid feeding pumps 253 has been described. When the same processing is performed on the head 211, for example, the inkjet head 211 and the liquid feed pump 253 to which inks of other colors are supplied, these may be performed simultaneously or individually in sequence. good.

Further, in the above embodiment, the inkjet recording device 100 having a recovery flow path 27 for returning the ink supplied to the inkjet head 211 and not ejected to the sub tank 251 has been described, but the device does not have the recovery flow path 27. You may. In this case, after the pressurization maintenance, the liquid feed pump 253 may be rotated in the reverse direction to collect a part of the ink, or the liquid may be discharged from the inkjet head 211 and wait until the normal pressure is restored. Alternatively, a waste liquid valve may be provided at the downstream end of the liquid feed common flow path 256 to drain excess ink.

Further, the inkjet recording device 100 has been described as a one-pass method using a line head, but even if the inkjet recording device 100 records an image by another method such as operating the inkjet head 211 with respect to the recording medium P. good. Further, the inkjet recording device 100 may be capable of adjusting the ink pressure in the inkjet head 211 without using the intermediate tank 262.
In addition, specific details such as the configuration, arrangement, control contents and their order shown in the above embodiment can be appropriately changed without departing from the spirit of the present invention.

10 Transport unit 11 Drive roller 12 Transport motor 14 Transport belt 20 Image forming unit 21 Head unit 211 Ink head 22 Carriage 221 Head drive unit 23 Carriage elevating unit 231 Motor driver 232 Elevating motor 233 Electromagnetic brake 234 Beam member 235 Support unit 24 Reading unit 27 Recovery flow path 29 Suction unit 292 Suction unit 292 Chamber 292a Liquid level sensor 293 Vacuum pump 294 Pressure sensor 30 Ink storage unit 31 Main tank 32 Supply pump 35 Rack 40 Control unit 401 CPU
402 RAM
403 ROM
403a Liquid feed adjustment table 404 Memory 41 Communication unit 42 Operation display unit 43 Notification operation unit 49 Bus 100 Inkjet recording device 251 Sub tank 251a Liquid volume sensor 251b Temperature sensor 252 Flow meter 253 Liquid feed pump 254 Filter 255 Degassing module 256 Common for liquid feed Flow path 256a Ink pressure sensor 257 Individual flow path 258 Individual flow path 259 Damper 260 Intermediate tank flow path 261 Intermediate tank flow valve 262 Intermediate tank 263 Common supply valve 265 Maintenance flow path 266 Maintenance flow path flow valve 270 Bypass valve 271 Check valve 272 Recovery common flow path 273 Recovery valve 274 Circulation valve 275 Recovery pumps 281 to 283, 291 Check valve P Recording medium

Claims (7)

An ink flow path connecting two or more predetermined number of recording units having nozzles for ejecting ink, a liquid feeding unit for feeding ink, the liquid feeding unit and the predetermined number of recording units, and the ink. It is a maintenance method of a recording unit in an inkjet recording apparatus including the predetermined number of switching units for switching whether or not ink can be supplied to each of the predetermined number of recording units in a flow path.
A liquid feed amount setting step in which the amount of liquid to be fed per unit time in which the ink pressure in the selected recording unit of the predetermined number of recording units is maintained within a predetermined reference range for a reference time or longer is defined as the liquid feed amount during pressurization. ,
A liquid feeding target switching step for switching whether or not ink can be supplied by the predetermined number of switching units depending on whether or not the predetermined number of recording units are selected.
A boosting step in which the selected recording unit is fed by the liquid feeding unit at a boosting liquid feeding amount defined as a liquid feeding amount per unit time when the ink pressure is boosted within the reference range.
A pressurization maintenance step in which the selected recording unit whose ink pressure is within the reference range in the boosting step is fed by the liquid feeding unit at the time of pressurization over the reference time. Including
The amount of liquid to be fed at the time of pressurization is equal to or more than the maximum value of the amount of liquid to be fed at the time of pressurization that can be determined in the step of setting the amount of liquid to be supplied, and the amount of liquid to be fed at the time of pressurization determined in the step of setting the amount of liquid to be supplied. A maintenance method for a recording unit, which is characterized in that a constant value is set in advance regardless of the value . The feed rate setting step, the selected maintenance method of the recording unit according to claim 1 Symbol mounting, characterized in that defining the pressurized feed volume based on the number of recording unit. When the number of the recording units set as the target of liquid transfer is larger than the predetermined upper limit number, the set recording units are each divided into a plurality of groups equal to or less than the upper limit number, and the plurality of times are selected. The maintenance method of the recording unit according to claim 1 or 2, wherein the liquid feeding target selection step is included. The recording unit according to any one of claims 1 to 3 , wherein the liquid feed amount setting step determines the liquid feed amount at the time of pressurization based on information relating to the viscosity of the ink to be fed. Maintenance method. The maintenance method for a recording unit according to any one of claims 1 to 4 , wherein the liquid feeding amount setting step determines the liquid feeding amount at the time of pressurization based on the temperature of the ink to be fed. The maintenance method for a recording unit according to any one of claims 1 to 5 , wherein the pressurization maintenance step is started based on a measured value of a pressure sensor for measuring ink pressure. Two or more predetermined number of recording units having nozzles for ejecting ink, and
The liquid feeding part that feeds ink and
An ink flow path connecting the liquid feeding unit and the predetermined number of recording units,
The predetermined number of switching units for switching whether or not ink can be supplied to each of the predetermined number of recording units in the ink flow path,
A control unit that controls the amount of liquid sent by the liquid feeding unit per unit time,
With
The control unit
The amount of liquid to be fed per unit time in which the ink pressure in the selected recording unit of the predetermined number of recording units is maintained within the predetermined reference range for the reference time or longer is defined as the amount of liquid to be fed during pressurization.
Whether or not ink can be supplied by the predetermined number of switching units is switched according to whether or not the predetermined number of recording units are selected.
The selected recording unit is fed by the liquid feeding unit at a pressure feeding amount determined as a liquid feeding amount per unit time when the ink pressure is increased within the reference range.
The selected recording unit whose ink pressure is within the reference range is fed by the liquid feeding unit at the pressurizing liquid feeding amount over the reference time.
The feature is that the pressure-pressing liquid feed amount is equal to or more than the maximum value defined as the pressurization liquid feed amount, and is predetermined to a constant value regardless of the pressurization liquid feed amount. Inkjet recording device.

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