WO2017169528A1

WO2017169528A1 - Inkjet recording device

Info

Publication number: WO2017169528A1
Application number: PCT/JP2017/008674
Authority: WO
Inventors: 秋田　宏; 拓三觜; 青木　哲志; 森川　修; 靖彦村松; 山崎　健
Original assignee: コニカミノルタ株式会社
Priority date: 2016-03-28
Filing date: 2017-03-06
Publication date: 2017-10-05
Also published as: EP3437884A4; JPWO2017169528A1; JP6908022B2; EP3437884B1; EP3437884A1

Abstract

Provided is an inkjet recording device capable of supplying ink to a head while responding to abnormalities in the ink storage level with more appropriate operation efficiency. The present invention is provided with: an inkjet head 211; a main tank 31; a sub-tank 251 for storing supply ink from the main tank 31; a supply pump 32 for sending ink from the main tank 31 to the sub-tank 251; a liquid delivery pump 253 for sending ink from the sub-tank 251 to the inkjet head 211; a reference sensor 251a, maximum sensor 251c, and minimum sensor 251b for determining whether ink of a prescribed reference storage amount, maximum storage amount, and minimum storage amount, respectively, are stored in the sub-tank 251; and a control unit 40 for determining whether to operate the supply pump 32 in accordance with the detection result of the reference sensor 251a, and performing a prescribed abnormality response operation in accordance with the detection results of the maximum sensor 251c and the minimum sensor 251b.

Description

Inkjet recording device

This invention relates to an ink jet recording apparatus.

Conventionally, there is an ink jet recording apparatus that forms an image by ejecting ink from nozzles and landing on a recording medium. Inkjet recording apparatuses can form images on a wide variety of recording media, and are widely used from home use to industrial large-volume image formation.

Some ink jet recording apparatuses have a configuration in which ink is moved from a main ink tank to a sub ink tank, and ink is replenished from the sub ink tank according to ink ejection in an ink jet head. In such an ink jet recording apparatus, when the ink in the sub ink tank decreases, the ink is replenished from the main ink tank. For example, Patent Document 1 includes an empty detection sensor that detects that the sub ink tank is empty, and a full tank detection sensor that detects that the sub ink tank is full. Even so, a configuration is disclosed in which ink is supplied from the main ink tank to the sub ink tank until full tank detection is performed when empty detection is performed.

JP 2005-306005 A

However, when there is an abnormality in the amount of ink stored in the second tank that receives ink from the first tank, which is the primary ink supply source, and sends ink to the inkjet head, In the ink supply control according to detection and full tank detection, the capacity of the second tank becomes smaller than the normal increase / decrease range of the ink storage amount, and the operation must be stopped immediately even if a small abnormality occurs. However, there is a problem that the operation efficiency is lowered by increasing the number of sensors more than necessary or increasing the capacity of the second tank.

An object of the present invention is to provide an ink jet recording apparatus capable of supplying ink to an ink jet head while dealing with an abnormal ink storage amount with more appropriate operation efficiency.

In order to achieve the above object, the invention according to claim 1
A recording head for ejecting ink;
A first tank for storing ink;
A second tank for storing ink supplied from the first tank;
First liquid feeding means for feeding ink from the first tank to the second tank;
One or a plurality of second liquid feeding means for feeding ink from the second tank to the recording head;
A reference sensor for determining whether or not a predetermined standard storage amount of ink is stored in the second tank;
An upper limit sensor for determining whether or not an upper limit storage amount larger than the standard storage amount is stored in the second tank;
A lower limit sensor for determining whether or not a lower storage amount of ink smaller than the standard storage amount is stored in the second tank;
A control unit;
With
The controller is
According to the detection result of the reference sensor, the presence or absence of operation of the first liquid feeding means is determined,
An inkjet recording apparatus that performs a predetermined abnormality handling operation according to detection results of the upper limit sensor and the lower limit sensor.

The invention described in claim 2 is the ink jet recording apparatus according to claim 1,
A recovery flow path for returning ink from the recording head to the second tank;
The difference between the upper limit storage amount and the standard storage amount is larger than the ink capacity of the ink flow path from the time when the second tank is sent to the time when the second storage tank returns to the second tank.

The invention described in claim 3 is the ink jet recording apparatus according to claim 1 or 2,
A notification unit for performing a predetermined notification operation;
The control unit operates the first liquid feeding means when the reference sensor does not detect the standard storage amount of ink, and operates the first liquid feeding means for a predetermined continuous reference time or more. When the reference sensor does not detect the standard storage amount of ink, the notification unit is configured to perform a notification operation.

According to a fourth aspect of the present invention, in the ink jet recording apparatus according to any one of the first to third aspects,
When the lower limit sensor does not detect the lower limit storage amount of ink, the control unit prohibits ink discharge from the recording head as the abnormality handling operation.

The invention described in claim 5 is the ink jet recording apparatus according to any one of claims 1 to 3,
The lower limit storage amount is determined to be equal to or greater than the maximum ink amount necessary for forming an image in the maximum range that can be set as an image formed by the recording head,
The control unit prohibits ink ejection from the recording head after forming an image in the middle of formation at a timing when the lower limit sensor no longer detects the lower limit storage amount of ink and before starting to form the next image. It is characterized by doing.

The invention according to claim 6 is the ink jet recording apparatus according to any one of claims 1 to 5,
The maximum ink feeding speed by the first liquid feeding means is higher than the ink feeding speed by the second liquid feeding means according to the maximum ink discharge amount from the recording head during operation of the recording head. It is characterized by being large.

The invention according to claim 7 is the ink jet recording apparatus according to any one of claims 1 to 6,
A third tank is provided between the second liquid feeding means and the recording head.

The invention according to claim 8 is the inkjet recording apparatus according to claim 3,
The control unit operates the first liquid feeding means when the reference sensor does not detect the standard storage amount of ink, and the first sensor until the reference sensor detects the standard storage amount again. The operation time of the liquid feeding means is counted, and the predetermined continuation reference time is set based on the result of one or more times of the counting.

According to the present invention, there is an effect that ink can be supplied to the inkjet head while dealing with an abnormality in the ink storage amount with more appropriate operation efficiency.

1 is an overall perspective view illustrating an inkjet recording apparatus according to an embodiment of the present invention. It is a figure explaining the ink flow path of an inkjet recording device. It is a block diagram which shows the function structure of an inkjet recording device. 6 is a flowchart illustrating a control procedure of ink supply control processing. 10 is a flowchart illustrating a modified example of ink supply control processing.

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

The inkjet recording apparatus 100 is a one-pass type apparatus having a plurality of line heads, 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 driving roller 11, a transport motor 12, a transport belt 14, and the like. The transport motor 12 rotates the drive roller 11 at a predetermined speed. An endless conveyance belt 14 is wound around the drive roller 11 together with a follower roller (not shown), and the conveyance belt 14 moves around by the rotation of the drive roller 11. A recording medium is placed on the conveying surface with the outer surface of the conveying belt 14 as a conveying surface, and the recording medium is conveyed in the conveying direction as the conveying belt 14 rotates.

The image forming unit 20 includes a carriage 22 and a carriage lifting / lowering unit 23, and a combination of these carriages 22 and the carriage lifting / lowering unit 23 is provided according to the number of ink colors (eight in this case). . Each of the carriages 22 extends in a direction intersecting with the conveyance direction (x direction) of the recording medium by the conveyance unit 10, in this case, in the orthogonal width direction (y direction). A plurality of inkjet heads 211 (see FIG. 2, recording heads) are arranged so as to be able to eject ink over the entire width of the recording medium that is arranged above (z direction) and forms a line head structure. The plurality of carriages 22 are provided at different positions in the transport direction. The carriage 22 is provided such that the distance from the conveyance surface to the upper side can be changed by the carriage lifting / lowering unit 23, and the distance from the conveyance surface of the inkjet head 211 is also changed as the carriage 22 moves.

The carriage lifting / lowering unit 23 changes the distance from the conveyance surface of the carriage 22. The carriage lift 23 includes a lift motor 232, an electromagnetic brake 233, a beam member 234, a support 235, and the like.
Two beam members 234 are provided substantially in parallel in the direction intersecting the conveyance direction (here, the orthogonal direction, ie, the width direction) on the upper portion of the conveyance belt 14 (on the conveyance surface side of the recording medium). Support portions 235 are fixed to both ends, respectively. A lift 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 operations of the lifting motor 232 and the electromagnetic brake 233 that are driven based on a control signal from the control unit 40 (see FIG. 3).

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

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

The ink storage unit 30 stores ink of each color used for image formation and supplies it to the inkjet head 211. Here, each configuration of the ink storage unit 30 is disposed in a dedicated rack 35 or the like, and is connected to the image forming unit 20 via a pipe or the like.

Next, a 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 relating to an ink flow path in the inkjet recording apparatus 100 of the present embodiment.

The ink storage unit 30 includes a main tank 31 (first tank), a supply pump 32 (first liquid feeding means), and the like.
The main tank 31 is provided for each ink color and 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 replaceable as a whole, and is formed to be detachable from the ink flow path to the supply pump 32 regardless of the operation state of the supply pump 32. That is, when the main tank 31 is attached while the supply pump 32 is in an operating state, the liquid supply of ink to the image forming unit 20 is immediately resumed.
Although it does not restrict | limit especially as the supply pump 32, For example, a diaphragm pump, a tube pump, etc. may 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 (second tank). An ink flow path (circulation flow path) that returns to the sub tank 251 after the ink delivered from the sub tank 251 reaches the inkjet head 211 is provided for the sub tank 251.

From the sub-tank 251 to the inkjet head 211 (liquid feeding channel), a flow meter 252, a liquid feeding pump 253 (second liquid feeding means), a filter 254, a deaeration module 255, and a liquid feeding common channel 256. A plurality of individual flow paths 257 branch from the liquid supply common flow path 256, and ink is sent to the inkjet head 211 through the individual supply valve 258 and the damper 259. Two ink jet heads 211 are connected to each damper 259.

Between the deaeration module 255 and the liquid feeding 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 passage 260 is provided with an intermediate tank flow valve 261, an intermediate tank 262 (third tank), a common supply valve 263, and the like.
A maintenance flow path distribution valve 266 is provided in the maintenance flow path 265.

In the recovery flow path 27 from the recovery port (outlet) of the inkjet head 211 to the sub tank 251, first, after the flow paths of the ink discharged from the two inkjet heads 211 respectively branched by the damper 259 merge, the check valve 271 is set. Then, it merges into the recovery common flow path 272. Then, the ink is returned from the recovery common flow path 272 to the sub tank 251 through the recovery valve 273 and the circulation valve 274. A recovery pump 275 is provided in parallel with the circulation valve 274.

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

The capacity of the sub tank 251 is smaller than the capacity of the main tank 31. The sub tank 251 is provided with a reference sensor 251a, a lower limit sensor 251b, an upper limit sensor 251c, and the like in order to detect the ink storage amount. The reference sensor 251a detects whether or not a standard storage amount of ink for determining whether or not ink is supplied from the main tank 31 to the sub tank 251 by the supply pump 32 (whether or not the supply pump 32 operates) is stored. That is, when the ink storage amount is smaller than the standard storage amount, the supply pump 32 is operated, and when the ink storage amount is larger than the standard storage amount, the supply pump 32 is stopped.

The lower limit sensor 251b detects whether or not the lower limit storage amount of ink for determining whether the operation of the inkjet head 211 is prohibited is stored. That is, the lower limit storage amount is smaller than the standard storage amount, and when the ink storage amount is smaller than the lower limit storage amount, the operation (ink ejection) of the inkjet head 211 is prohibited. If the ink is properly supplied from the main tank 31 to the sub tank 251, the ink amount in the sub tank 251 does not greatly decrease from the standard storage amount. Therefore, an abnormal situation in which ink supply is not performed is below the lower limit storage amount. Means the occurrence of

The upper limit sensor 251c detects whether or not an upper limit storage amount of ink indicating a risk of overflowing the sub tank 251 is stored. The upper limit storage amount is set to be larger than the sum of the standard storage amount and the ink capacity of the entire circulation channel (liquid supply channel, inkjet head 211 and recovery channel 27). Even if it is returned to the sub tank 251 without being discharged at all, the upper limit storage amount is not exceeded. Therefore, exceeding the upper limit storage amount may cause an abnormal situation such as excessive ink supply or mixing other than ink. means.
In the ink jet recording apparatus 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 fed from the sub tank 251 to the inkjet head 211 side by the liquid feed pump 253. The measurement value of the flow meter 252 is used here when status display and history information is held by the operation display unit 42 (see FIG. 3), and is not used for abnormality detection. It is good also as being used for calculation of the notification reference time.

The liquid feed pump 253 sends ink inside the sub tank 251 to the filter 254 and its downstream side, that is, the ink jet head 211 side (liquid feed flow path) at a predetermined liquid feed speed (liquid feed amount per hour). Here, one liquid feed pump 253 is provided for the sub tank 251 and supplies ink to all the ink jet heads 211. However, each of the predetermined number of ink jet heads 211 is divided into a plurality of blocks and is separately provided. Ink may be supplied from the sub tank 251 by the liquid feed pump 253. The liquid feeding capability of the liquid feeding pump 253 is not limited as long as it can sufficiently supply the maximum ink discharge amount per hour by the ink jet head 211 accompanying the image forming operation, and the ink supply speed according to this maximum ink discharge amount Is smaller than the maximum liquid feeding speed of the supply pump 32. Accordingly, the liquid feed pump 253 may have a liquid feed capacity smaller than that of the supply pump 32, but the same liquid supply pump 32 as that of the supply pump 32, that is, the same type may be used. In this case, it is not necessary to operate the liquid feeding pump 253 at the maximum ink feeding speed even in a situation where the most ink is being ejected by the inkjet head 211 (during formation of a solid image).

The filter 254 removes foreign matters such as dust and dust, contaminants, and large bubbles in the ink. As described above, the sub tank 251 is open to the atmosphere, and these foreign substances, impurities, and bubbles can be mixed. Therefore, the filter 254 prevents these from being sent to the inkjet head 211.

The deaeration module 255 removes air (gas) contained in the ink. As the deaeration module 255, for example, a structure is used in which the air in the ink is selectively sucked to the vacuum region side by bringing the ink and the vacuum region into contact with each other through a deaeration film. As the deaeration film, in order to increase the contact area with the ink efficiently and to make the contact with the ink more evenly, for example, the deaeration film can have a large number of hollow fine yarn structures whose inside is in a vacuum state.
Here, air on the vacuum region side of the degassing module 255 is sucked by the vacuum pump 293. The vacuum region here does not necessarily need 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 atmospheric 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 deaeration module 255 is connected to the chamber 292 through a check valve 291. The ink that slightly permeates the deaeration membrane or leaks to the vacuum region at a time when the deaeration membrane is broken flows into the bottom of the chamber 292 and is stored. The ink collected at the bottom of the chamber 292 is detected by the liquid amount sensor 292a to determine whether or not an abnormal amount has leaked. When the abnormality is detected, the operation of the vacuum pump 293 or each part is stopped, or the vacuum region is It is communicated. As described above, the chamber 292 is used as a trap for leaked ink, and the leaked ink is not allowed to reach the vacuum pump 293, thereby preventing failure or breakage of the vacuum pump 293.

As the liquid quantity sensor 292a, in addition to directly measuring the liquid quantity, a weight change of the chamber 292 is measured, or a member that changes according to the weight change, for example, an actuator that is deformed by a load according to the weight of the chamber 292. For example, a signal that is optically, electrically, or magnetically measured according 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 provided in common to the deaeration module 255 in the circulation channel provided for each color ink. , The structure is such that it merges downstream of the check valve 291 (on the chamber 292 side). That is, when ink of a certain color leaks from the deaeration module 255, the check valve 291 causes the ink of the certain color to flow into the vacuum region side of the deaeration module 255 of the circulation channel related to the other color ink. Is prevented.

The intermediate tank flow valve 261 is provided in the vicinity of the inlet of the intermediate tank flow path 260 separated from the maintenance flow path 265 downstream of the deaeration module 255, and is opened and closed according to whether or not ink can flow into the intermediate tank flow path 260. The The intermediate tank flow path 260 is opened when ink is supplied to the inkjet head 211 during normal image formation. The intermediate tank circulation valve 261 and other valves whose open / closed state is controlled are not particularly limited. Here, however, an electromagnetic valve, for example, a plunger (movable iron piece) provided in the ink flow path is used as an electromagnetic force. A solenoid valve or the like that switches between opening and closing of the flow path by moving by a spring force is used, and the opening and closing operation is performed according to the voltage applied by the control of the control unit 40 (see FIG. 3). In FIG. 2, the black-colored valves such as the intermediate tank circulation valve 261 are valves that are closed in a normal state (when a ground voltage is supplied or when no voltage is supplied). Also, white valves such as the common supply valve 263 are valves that are opened in a normal state.

The intermediate tank 262 is a tank having a smaller capacity than the sub tank 251 and is used to keep the ink in the inkjet head 211 at an appropriate back pressure (negative pressure), that is, a pressure lower than the atmospheric pressure. For this purpose, the intermediate tank 262 is formed of a flexible material, can be appropriately deformed by the pressure difference between the ink pressure and the external pressure, and from the nozzle surface on which the nozzle openings of the inkjet head 211 are arranged. Is also provided at a slightly lower position in the vertical direction. As a result, the ink naturally leaks from the nozzle opening unless the ink is intentionally ejected by further applying pressure to the ink in the pressure chamber in the liquid feed pump 253 or the inkjet head 211. do not do. On the other hand, when ink is ejected from the nozzle opening and the ink in the inkjet head 211 decreases, the ink flows from the intermediate tank 262 to the inkjet head 211 in accordance with the decrease amount (ink ejection amount).

The intermediate tank 262 is provided with an intermediate upper limit sensor 262a and an intermediate reference sensor 262b.
The intermediate reference sensor 262b detects an intermediate reference ink amount appropriately set to obtain an appropriate back pressure. The presence / absence of the operation of the liquid feed pump 253 is appropriately controlled in accordance with the presence / absence of detection of the intermediate reference ink amount by the intermediate reference sensor 262b. Further, the intermediate upper limit sensor 262a detects an upper limit ink amount determined so as not to be dangerous for the maintenance of the intermediate tank 262. Normally, when the ink amount in the intermediate tank 262 increases more than usual and the ink pressure increases, the check valve 283 is opened and the ink is returned to the sub tank 251, but the check valve 283 does not function normally. For example, all the processes related to the ink supply operation can be stopped or other appropriate processes can be performed according to the detection by the intermediate upper limit sensor 262a.

The maintenance flow passage valve 266 switches whether the ink sent by the liquid feed pump 253 can flow into the maintenance flow passage 265 or not. As shown here, the maintenance flow passage valve 266 and the intermediate tank flow valve 261 can be closed simultaneously. For example, even during an image forming operation, if the amount of ink in the intermediate tank 262 is within an appropriate range and it is not necessary to supply additional ink to the intermediate tank 262 by the liquid feed pump 253, maintenance is performed. Both the flow path distribution valve 266 and the intermediate tank distribution valve 261 are closed.

The maintenance flow path 265 is pressurized and sent to the liquid feed common flow path 256 and the inkjet head 211 by the liquid feed pump 253 for the purpose of introducing ink, discharging air (bubbles), and flushing the cause of clogging. Used when sending ink as it is. For example, by closing all the individual supply valves 258 and feeding pressurized ink while opening the bypass valve 270, the ink is introduced into the liquid feeding common flow path 256, and the ink is flowed to the inside. Air flows out to the recovery flow path 27 and the sub tank 251. Further, the ink is filled in the ink flow path in each inkjet head 211 by sending the pressurized ink by the liquid feed pump 253 with both the individual supply valve 258 and the recovery valve 273 open. Further, the pressurized ink is sent out by the liquid feed pump 253 with the individual supply valve 258 opened and the recovery valve 273 closed, thereby discharging the pressurized ink from each nozzle of the inkjet head 211. Then, the bubbles in the nozzles are discharged, and the cause of the clogging of the nozzle openings, for example, the solidified ink mass is discharged to eliminate the clogging.

The common supply valve 263 is particularly pressurized through the maintenance flow path 265 by switching whether to supply ink from the intermediate tank 262 to the liquid supply common flow path 256 and each ink jet head 211 or not. When ink is supplied to the common flow path, the ink is prevented from flowing back to the intermediate tank 262.

The individual supply valve 258 switches whether ink can be supplied from the liquid supply common flow path 256 to the individual flow path 257 branched from the liquid supply common flow path 256 and communicating with the plurality of inkjet heads 211. While these individual supply valves 258 are all opened during the normal image forming operation, when the ink in the intermediate tank 262 and the liquid feed common flow path 256 is returned to the sub tank 251 and collected without taking it outside, these individual supply valves 258 are opened. The supply valve 258 is closed and the bypass valve 270 is opened. In addition, when ink is selectively supplied to some of the inkjet heads 211 for inspection or cleaning of some of the inkjet heads 211, the ink is provided in the individual flow path 257 communicating with the partial inkjet head 211. Only the individual supply valve 258 is opened, and the other individual supply valves 258 are closed.
Here, four individual flow paths 257 are described as an example, but this number can be set as appropriate within a range that does not cause a problem in the ink supply to the inkjet head 211 and the discharge operation from the nozzles.

The damper 259 is a buffer unit that reduces pressure fluctuations that occur according to the ink discharge status from the plurality of inkjet heads 211 and the liquid supply (ink pressurization) status from the liquid supply pump 253. In this way, the pressure fluctuation relating to the operation of the other inkjet head 211 and the liquid feed pump 253 is suppressed, and pressure is applied to the ink in the inkjet head 211 with an appropriate pressure pattern when ink is ejected from the inkjet head 211. The ink is ejected normally.

The inkjet head 211 has a plurality of nozzles arranged. The ink supplied from the damper 259 to the inkjet head 211 is further branched into an ink flow path communicating with each nozzle. A pressure chamber (not shown) is provided in the ink flow path, and ink is ejected by applying pressure with an appropriate waveform to the ink in the pressure chamber, or ink that is not ejected is appropriately vibrated in the nozzle. This prevents the ink from drying or changing in quality. As a method of applying pressure to the ink in the pressure chamber, various known methods can be selected. Here, the pressure chamber is deformed by applying a voltage using a piezoelectric element or a diaphragm, and the pressure to the ink is changed. It has a piezo structure.

The check valve 271 allows ink discharged from the inkjet head 211 without being ejected by the nozzles to flow into the common recovery common channel 272, while ink from the recovery common channel 272 to the inkjet head 211. Prevent backflow. That is, the ink discharged from some of the inkjet heads 211 does not flow back to the other inkjet heads 211.

The recovery common flow path 272 that joins the ink discharged without being ejected from the inkjet head 211 and flows to the sub tank 251 side has substantially the same configuration as the liquid supply common flow path 256, and is formed in a tube shape, for example. ing. The liquid feeding common flow channel 256 and the recovery common flow channel 272 are both formed sufficiently thicker (the cross-sectional area is larger) than the individual flow channel 257, so that the flow rate related to the change in the amount of ink supplied to the individual flow channel 257. And the spread of the influence of the change in ink pressure is suppressed.

The recovery valve 273 switches whether ink is returned from the recovery common flow path 272 to the sub tank 251. Further, the recovery valve 273 is closed when the bypass valve 270 is opened, so that the ink flowing from the liquid supply common flow path 256 through the bypass valve 270 does not return to the recovery common flow path 272. To.

The ink that has passed through the bypass valve 270 or the recovery valve 273 is returned to the sub tank 251 through the circulation valve 274 or the recovery pump 275. When the ink that has been once delivered from the liquid feed pump 253 and is not discharged from the nozzles of the inkjet head 211 is extracted and returned to the sub tank 251, the circulation valve 274 is closed and the recovery pump 275 is operated. Thereby, ink remaining in each part such as the inkjet head 211 and the intermediate tank 262 is sucked and returned to the sub tank 251, so that the ink can be removed from the inside of the inkjet head 211 and the intermediate tank 262. .

Further, the recovery pump 275 sucks not only ink but also air in the ink flow path. When the ink is not supplied into the circulation channel in the initial state or after restarting after maintenance, etc., the air in the circulation channel is once sucked by the recovery pump 275, and in particular, the air in the intermediate tank 262 is substantially reduced. After the ink is completely removed, the ink is introduced into the intermediate tank 262 by the liquid feed pump 253, so that air remains in the intermediate tank 262 to generate unnecessary pressure, or the air is mixed with the ink. It is avoided that a discharge failure or the like is caused by flowing out and being sent to the inkjet head 211. Normally, when ink is introduced, air removal by the collection pump 275, ink collection, and ink introduction by the liquid feed pump 253 are repeated a plurality of times, so that the inside of the circulation channel, particularly from the sub tank 251 to the inkjet head 211, is repeated. Ink can be introduced while more reliably preventing air from remaining between the two.

When it is not necessary to remove the ink inside the inkjet head 211 or the intermediate tank 262 and the ink sent by the liquid feed pump 253 is simply circulated, the circulation valve 274 is opened without operating the recovery pump 275. Thus, the ink circulation flow is generated only by the liquid supply pressure of the liquid supply pump 253.

It should be noted that a discharge valve that can be opened by the user to discharge ink is provided on the downstream side of the filter 254, the downstream of the intermediate tank 262, and the liquid supply common flow path 256 as necessary.

Next, a functional configuration of the ink jet recording apparatus 100 of the present embodiment will be described.
FIG. 3 is a block diagram showing a functional configuration of the inkjet recording apparatus 100.
The inkjet recording apparatus 100 includes the transport motor 12, the supply pump 32, the liquid feed pump 253, the recovery pump 275, the vacuum pump 293, the reference sensor 251a, the lower limit sensor 251b, the upper limit sensor 251c, the intermediate upper limit sensor 262a, and the intermediate reference sensor 262b. , Pressure sensor 294, liquid volume sensor 292a, intermediate tank flow valve 261, maintenance flow passage flow valve 266, common supply valve 263, individual supply valve 258, bypass valve 270, recovery valve 273, circulation valve 274, electromagnetic brake 233, and In addition to the raising / lowering motor 232, the control part 40, the communication part 41, the operation display part 42, the head drive part 24, the motor driver 231, the alerting | reporting operation part 43 (notification part), etc. are provided.

The control unit 40 controls the overall operation of the inkjet recording apparatus 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, and controls the conveyance of the recording medium, the supply of ink, the ejection of ink, the maintenance operation, and the like in the inkjet recording apparatus 100. The CPU 401 performs various processes related to image formation based on image data, status signals of each unit, clock signals, and the like according to a program read from the ROM 403.

The RAM 402 provides a working memory space to the CPU 401 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 the ink supply control described above, and the initial setting data includes an initial value of a notification reference time (predetermined continuation reference time). This notification reference time is a reference time for detecting an abnormality in the operation time of the supply pump 32 (the duration of the liquid feeding operation) when ink is supplied from the main tank 31 to the sub tank 251. That is, when the operation time of the supply pump 32 exceeds the notification reference time, the supply pump 32 stops operating, i.e., when the standard storage amount of ink is not stored, the ink supply abnormality, mainly the main It is determined that the ink in the tank 31 has run out. As an initial value of the notification reference time, an assumed maximum operation time, for example, an ink consumption speed (ink discharge amount per hour) at the time of forming an image that consumes the most ink (that is, a solid image), and the supply pump 32 are used. Depending on the difference from the ink feeding speed in the normal operation, the time required for recovering the ink amount of the standard storage amount can be set with a slight margin.

In addition, the ROM 403 includes a non-volatile memory that can be overwritten and updated, and a notification reference time 403b that holds the latest setting value of the notification reference time that is updated and maintained as needed, and a transmission when the supply pump 32 operates. The continuation time of the liquid operation, that is, supply time history data 403a that is history data of the ink supply time to the sub tank 251 is stored. This history data can be set so that only data within the most recent predetermined period or a predetermined number of times (one or a plurality of times) is retained. The memory 404 includes a RAM that temporarily stores image data to be formed. In the actually formed image, the ink consumption speed is lower than that in the above-described image formation that consumes the most ink. Therefore, the liquid feeding operation by the supply pump 32 necessary to recover the ink amount of the standard storage amount is performed. Since the duration is assumed to be shorter, it is assumed that the ink has run out more appropriately and quickly by acquiring the measured value (counting result) of this duration and setting and adjusting the notification reference time during the output of the same image. In this case, it is possible to notify abnormality. The specific adjustment method is not particularly limited. For example, the latest value obtained by multiplying a predetermined value by the maximum value, the maximum value, or the average value multiplied by a predetermined coefficient, which has been set last time. Or a weighted average of the last predetermined number of average values or maximum values or the weighted average value multiplied by a predetermined coefficient, etc. Can be mentioned.
When the image to be formed is switched, each actual measurement value in the stored supply time history data 403a may be deleted to return the notification reference time to the initial value.

The head drive unit 24 generates and outputs a drive voltage signal that causes the pressure chamber (piezoelectric element) to deform in order to properly eject ink from the nozzles in each inkjet head 211. The head driving unit 24 selects a voltage waveform pattern stored in advance based on a control signal from the control unit 40 to generate a power amplification drive voltage signal, and each of the head driving unit 24 according to image data input from the memory 404. Whether to output a drive voltage signal to the piezoelectric element is switched.
The wiring related to the head driving unit 24 is formed together with the ink flow path in the inkjet head 211, and is formed partially separately.

The motor driver 231 outputs a drive signal to the electromagnetic brake 233 and the lifting motor 232 according to the control signal from the control unit 40, loosens the electromagnetic brake 233 and operates the lifting motor 232 to move the carriage to a desired position. Or the elevator motor 232 is stopped and the electromagnetic brake 233 is used to fix the carriage.

The communication unit 41 is a communication interface that controls a communication operation with an external device. As the communication interface, for example, one or a plurality of communication interfaces such as a LAN board and a LAN card corresponding to various communication protocols are included. The communication unit 41 acquires image data to be formed and setting data (job data) related to image formation from an external device based on the control of the control unit 40, and transmits status information and the like to the external device. I can do it.

The operation display unit 42 displays a status, an operation menu, and the like of the ink jet recording apparatus 100 according to a control signal from the control unit 40, and accepts a user operation and outputs it 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 unit is provided so as to overlap with a display screen as a display unit. The control unit 40 displays various menus for accepting commands by the status and touch sensor on the liquid crystal display unit, and displays information on the contents and position of the displayed menu and the user's touch operation detected by the touch sensor. A control operation is performed to cause each unit of the inkjet recording apparatus 100 to perform a corresponding process.

The notification operation unit 43 performs a predetermined notification operation according to the control signal of the control unit 40. As a structure which performs alerting | reporting operation | movement, the beep sound generation part etc. which generate | occur | produce the LED lamp which emits the light of a predetermined color, and / or a beep, etc. are mentioned, for example.
In addition to these, the inkjet recording apparatus 100 has a line sensor for detecting an image quality abnormality (defect) of an image formed on the recording medium and the supplied recording medium are not normally placed on the conveyance surface. A reading unit such as a mounting abnormality detection sensor for detecting the above may be provided.

The bus 49 is a path for exchanging signals by electrically connecting the above components.

Next, an ink supply control operation in the inkjet recording apparatus 100 of the present embodiment will be described.
In the ink jet recording apparatus 100, the operation of the supply pump 32 is controlled only according to whether or not the standard storage amount of ink is detected by the reference sensor 251a. On the other hand, abnormal ink supply from the main tank 31 based on the detection result of the lower limit sensor 251b, that is, mainly determines whether or not the main tank 31 is out of ink, determines whether or not the ink jet head 211 is operable, and further determines whether or not the upper limit sensor operates. Ink inflow abnormality to the sub tank 251 is detected according to the detection result of 251c, and notification operation and operation control of each part are performed as an operation corresponding to each abnormality (abnormality response operation).

FIG. 4 is a flowchart illustrating a control procedure by the control unit 40 of the ink supply control process executed in the ink jet recording apparatus 100 of the present embodiment.
This ink supply control process is started when the operation of the ink jet recording apparatus 100 is started, and is continuously executed until the operation is stopped due to normality or abnormality detection.

When the ink supply control process is started, the control unit 40 (CPU 401) first has the detection result of the upper limit sensor 251c in the off state, that is, has not detected the upper limit storage amount of ink (the ink storage amount of the sub tank 251). Is less than the upper limit storage amount) (step S101). If it is determined that it is not in the off state (“NO” in step S101), since the ink storage amount is equal to or greater than the upper limit storage amount, the control unit 40 stops the operation of the inkjet head 211 and all the pumps, A predetermined notification operation is performed on the display screen of the operation display unit 42 or the notification operation unit 43 (step S102). Then, the control unit 40 ends the ink supply control process.

If it is determined that the detection result of the upper limit sensor 251c is in the off state (“YES” in step S101), the control unit 40 indicates that the detection result of the lower limit sensor 251b is in the on state, that is, the ink with the lower limit storage amount. Is detected (the ink storage amount of the sub tank 251 is equal to or greater than the lower limit storage amount) (step S111). If it is determined that it is not in the ON state (“NO” in step S111), the ink storage amount is less than the lower limit storage amount, so the control unit 40 prohibits the operation of the inkjet head 211 and performs the image forming operation. If it is in the middle, the operation of the inkjet head 211 is stopped. Further, the control unit 40 causes the display screen of the operation display unit 42 and the notification operation unit 43 to perform a predetermined notification operation (step S112). Then, the process of the control unit 40 proceeds to step S122.
At this time, the control unit 40 may stop the operation of the supply pump 32. In this case, or when the operation of the supply pump 32 has already been stopped before the operation of step S112, the user replaces the main tank 31 and then performs a predetermined input operation to the operation display unit 42 to supply pump. 32 operations need to be resumed. When the operation of the inkjet head 211 is reset when the operation of the supply pump 32 is resumed, the user again issues a command related to image formation.

When it is determined that the detection result of the lower limit sensor 251b is in the on state (“YES” in step S111), the control unit 40 indicates that the detection result of the reference sensor is in the on state, that is, the ink with the standard storage amount. Is detected (the ink storage amount of the sub tank 251 is equal to or larger than the standard storage amount) (step S121). When it is determined that it is not in the on state (“NO” in step S121), the control unit 40 determines whether or not the supply pump 32 is in a liquid feeding operation (step S122). When it is determined that the liquid feeding operation is not being performed (“NO” in step S122), the control unit 40 starts the liquid feeding operation of the supply pump 32 and starts counting the liquid feeding operation time (step S1). S123). Then, the process of the control unit 40 returns to step S101.

When it is determined that the liquid feeding operation of the supply pump 32 is being performed (“YES” in step S122), the control unit 40 determines whether or not the liquid feeding operation time being counted is within the notification reference time. It discriminate | determines (step S124). When it is determined that it is within the notification reference time (“YES” in step S124), the process of the control unit 40 returns to step S101. When it is determined that it is not within the notification reference time, that is, the notification reference time has been exceeded (“NO” in step S124), the control unit 40 detects that the ink supply is abnormal or more directly. The display screen of the operation display unit 42 and the notification operation unit 43 are informed that the tank 31 should be replaced (step S125). Then, the process of the control unit 40 returns to step S101. At this time, in the ink jet recording apparatus 100 of the present embodiment, the operation of the supply pump 32 is continued. Therefore, when the main tank 31 is replaced, the ink supply is immediately resumed, and the reference sensor 251a returns to the ON state when the ink amount returns to the standard storage amount. After the process of step S125, the main tank 31 is not replaced and the ink is not supplied to the sub tank 251, and before the branching to “NO” in the determination process of step S111, the supply pump 32 is turned on for a predetermined operation upper limit time. It can also be configured to stop the operation. In this case, as described above, the user needs to restart the operation of the supply pump 32 by a predetermined input operation to the operation display unit 42.

When it is determined in the determination process in step S121 that the determination result of the reference sensor 251a is in the ON state (“YES” in step S121), the control unit 40 determines whether the supply pump 32 is in a liquid feeding operation. It is determined whether or not (step S126). When it is determined that the liquid feeding operation is not in progress (“NO” in step S126), the process of the control unit 40 returns to step S101.

When it is determined that the supply pump 32 is in the liquid feeding operation (“YES” in step S126), the control unit 40 stops the liquid feeding operation of the supply pump 32 (step S127). The control unit 40 acquires the operation time of the supply pump that has been counted and adds or updates the supply time history data 403a, and updates the notification reference time using the latest supply time history data 403a as necessary. The information is set and stored as the notification reference time 403b (step S128). Then, the process of the control unit 40 returns to step S101.

[Modification]
FIG. 5 is a flowchart illustrating a modified example of the ink supply control process.
When the flowchart of this modification is executed, the lower limit storage amount detected by the lower limit sensor 251b is set slightly higher than the above case. That is, even after the lower limit storage amount is cut off, image formation can continue within a predetermined limit, so that the lower limit storage amount is set higher by an amount corresponding to the predetermined limit.

In the ink supply control process of this modification, the process of step S112 is divided into the processes of steps S112a to S112c with respect to the ink supply control process described above, and the processes of steps S123 to S125 are replaced with the processes of steps S123a to S125a. In addition, processes of steps S131, S132, S141, S142, and S151 are added. Moreover, the order of some processes is changed. The other processes are the same, and the same process contents are denoted by the same reference numerals and detailed description thereof is omitted.

In the ink supply control process of the modified example, when it is determined in the determination process in step S111 that the lower limit sensor is not in the on state (“NO” in step S111), the control unit 40 performs an ink out notification operation. (Step S112a). At this time, the control unit determines whether or not the formation of the image in the middle of formation has been completed, that is, whether or not it is a good timing for image formation (step S112b).
The image in the middle of formation as used herein refers to, for example, the entire formed image corresponding to the entire image formable range of the recording medium divided, such as one sheet of paper, or the same image is repeatedly formed a plurality of times. It corresponds to unit image data set for each forming range, such as a single image forming range, and may include a plurality of individual partial images and the same image pattern. That is, the lower limit storage amount is determined to be equal to or larger than the maximum ink amount (that is, the ink amount necessary for a solid image) necessary for image formation of the maximum size (maximum range) that can be set by the inkjet recording apparatus 100 as the unit image data. .

If it is determined that the formation of the image being formed is not completed (the image is being formed) (“NO” in step S112b), the processing of the control unit 40 proceeds to step S131. If it is determined that the image formation in the middle of the formation has been completed (the image formation is in a state of being divided. Before the formation of the next image after the formation of the image in the middle of formation), it is determined (step S112b). The control unit 40 prohibits the subsequent operation of the inkjet head 211 and stops the operation of the inkjet head 211 in operation (step S112c). Then, the process of the control unit 40 proceeds to step S131.

If it is determined in the determination process in step S121 that the reference sensor is not in the on state (“NO” in step S121), the process of the control unit 40 proceeds to step S131.
When the process proceeds to step S131, the control unit 40 determines whether or not an elapsed time after the reference sensor is turned off is “0” (step S131). When it is determined that the elapsed time is “0” (“YES” in step S131), the control unit 40 starts the operation of the supply pump 32, and also the elapsed time and the liquid feeding operation time of the supply pump 32. Counting with (operation time) is started (step S132). Then, the process of the control unit 40 returns to step S101.

When it is determined that the elapsed time is not “0” (“NO” in step S131), the control unit 40 determines whether or not the elapsed time has become the notification reference time (step S124a). The equal “=” here does not mean strictly equal, but means that the elapsed time is the first determination process after the notification reference time has passed. When it is determined that the notification reference time is reached (“YES” in step S124a), the control unit 40 causes the display screen of the operation display unit 42 or the notification operation unit 43 to perform a notification operation that prompts replacement of the main tank. At the same time, the operation of the supply pump 32 is stopped (step S125a). At this time, the counting of the liquid feeding operation time is stopped and the value is initialized. Then, the process of the control unit 40 returns to step S101.

The elapsed time is not the timing when the notification reference time is reached, that is, the elapsed time is less than the notification reference time, or the notification reference time has already passed (it has already been determined that the notification reference time has been reached). If it is determined (“NO” in step S124a), the control unit 40 determines whether or not the supply pump 32 is operating (step S122). If it is determined that it is operating (“YES” in step S122), the control unit 40 determines whether or not the liquid feeding operation time of the supply pump 32 is equal to or longer than the upper limit duration time (step S141). . This continuous upper limit time corresponds to the maximum estimated time that the reference sensor 251a is assumed to be turned on when the supply pump 32 operates in each situation, or a time that includes a slight margin. That is, as the elapsed time becomes longer, there is a possibility that the ink storage amount is further lower than the standard storage amount. Therefore, the continuous upper limit time is a variable that becomes longer according to the continuous time. The maximum estimated time is the ink from the minimum ink storage amount assumed according to the elapsed time to the standard storage amount when the supply pump 32 is continuously operated at the time of image formation in which the ink consumption is maximum. Calculated as the time required to recover the amount.

When it is determined that the liquid feeding operation time is not equal to or longer than the continuous upper limit time (“NO” in step S141), the process of the control unit 40 returns to step S101. When it is determined that the duration upper limit time is exceeded ("YES" in step S141), the control unit 40 stops the operation of the supply pump 32 (step S142). At this time, the control unit 40 stops counting the liquid feeding operation time and initializes the value of the liquid feeding operation time. Then, the process of the control unit 40 returns to step S101.

If it is determined in step S122 that the supply pump 32 is not operating ("NO" in step S122), the control unit 40 issues an operation resumption command for the supply pump 32 to the operation display unit 42. It is determined whether it is acquired based on the input operation or it is the operation resumption timing of the supply pump 32 (step S151). Here, the operation resumption command is accepted at any time by performing a predetermined operation on the operation display unit 42 when the user replaces the main tank 31. Further, as described above, when the operation of the supply pump 32 is stopped while the reference sensor 251a is off, the operation of the supply pump 32 is automatically restarted after a predetermined time has elapsed. . The predetermined time may be a fixed time from the timing when the operation is stopped, or may be a fixed time from the timing when the previous operation is started or restarted. Alternatively, the predetermined time may be extended each time the operation start / restart and stop of the supply pump 32 are repeated.

If it is determined that the operation resumption command has not been acquired and it is not the operation resumption timing of the supply pump 32 (“NO” in step S151), the processing of the control unit 40 returns to step S101. When it is determined that the operation resumption command has been acquired or the operation resumption timing of the supply pump 32 is reached (“YES” in step S151), the control unit 40 resumes the operation of the supply pump 32 and sends the operation. The liquid operation time is counted again from “0” (step S123a). Then, the process of the control unit 40 returns to step S101.

If it is determined in step S121 that the reference sensor 251a is on (“YES” in step S121), the elapsed time is stopped and the value is initialized. Further, when the supply pump is stopped in the process of step S127, the counting of the liquid feeding operation time is stopped and the value is initialized.

As described above, the inkjet recording apparatus 100 of the present embodiment includes the inkjet head 211 that ejects ink, the main tank 31 that stores ink, the sub tank 251 that stores ink supplied from the main tank 31, and the main tank. 31, a supply pump 32 for feeding ink from the sub tank to the sub tank 251, one or a plurality of liquid feed pumps 253 for feeding ink from the sub tank to the inkjet head 211, and a predetermined standard storage amount of ink are stored in the sub tank 251. A reference sensor 251a for determining whether or not there is an upper limit sensor 251c for determining whether or not an upper limit storage amount of ink larger than the standard storage amount is stored in the sub tank, and a lower limit storage amount smaller than the standard storage amount in the sub tank 251. Lower limit for determining whether ink is stored The control unit 40 determines whether or not the supply pump 32 operates according to the detection result of the reference sensor 251a, and determines the predetermined value according to the detection results of the upper limit sensor 251c and the lower limit sensor 251b. Perform the error handling operation.
As described above, in the ink jet recording apparatus 100, the operation of the supply pump 32 is determined in accordance with the detection of the reference sensor 251a that detects the standard storage amount, so that the operation control is easily performed without using a plurality of parameters. Further, it is not necessary to increase the number of sensors necessary for determining whether the supply pump 32 is operating or not more than necessary.
In addition, since the ink storage amount does not deviate significantly from the standard storage amount during normal operation, the margin (volume difference) between the upper limit storage amount and the lower limit storage amount determined above and below the standard storage amount is larger than the sub tank capacity. Easy to take. This eliminates the need to immediately stop the operation of the inkjet head 211 when a slight abnormality occurs, particularly when an ink supply abnormality occurs due to the ink out of the main tank 31, while inkjet recording such as an upper limit storage amount or less than a lower limit storage amount. It is possible to reliably detect an ink storage amount at a level that causes a problem in the operation of the apparatus 100 and appropriately perform an abnormality handling operation such as a notification operation or an operation prohibition of the inkjet head 211.
Therefore, in the ink jet recording apparatus 100, it is possible to supply ink to the ink jet head while dealing with an abnormality in the ink storage amount of the sub tank 251 with more appropriate operation efficiency.

In addition, since it is not necessary to provide a storage amount sensor in the main tank 31, the configuration of the main tank 31 to be replaced becomes easy, and the main tank 31 can be easily attached and detached at the time of replacement. Similarly, since it is not necessary to integrate the flow rate from the main tank 31 to acquire the remaining amount of the main tank 31, a notification operation is performed at a more appropriate timing while suppressing an error in the remaining amount. Ink discharge operation can be prohibited.

Further, a recovery flow path 27 for returning ink from the inkjet head to the sub tank 251 is provided, and the difference between the upper limit storage amount and the standard storage amount is determined by the ink capacity of the ink flow path from the time when the ink is sent from the sub tank 251 to the return to the sub tank 251. Is also big.
Therefore, in the ink jet recording apparatus 100, all the ink in the ink flow path (circulation flow path) can be normally collected in the sub tank 251 for maintenance or the like, and the sub tank is really caused by an abnormality in the supply pump 32, the sub tank 251 and the like. It is possible to appropriately determine an abnormal situation in which there is a possibility that 251 overflows. Also, normally, it is not assumed that the ink storage amount will increase significantly before and after the standard storage amount only with the reference sensor 251a, so that the capacity margin of the sub tank 251 is increased more than necessary even if the ink recovery in the ink flow path is expected. It can be set to an appropriate size without taking.

In addition, the control unit 40 includes a notification operation unit 43 that performs a predetermined notification operation. The control unit 40 operates the supply pump 32 when the reference sensor 251a does not detect the standard storage amount of ink, and operates the supply pump 32. When the reference sensor 251a does not detect the standard storage amount of ink for a predetermined continuation reference time or longer, the notification operation unit 43 performs a notification operation.
That is, when the ink storage amount in the sub tank 251 does not recover as expected, the ink supply abnormality, mainly the ink out of the main tank 31, has occurred, and this can be detected easily and quickly by detecting only the reference sensor 251a. Then, it is possible to prompt the user to replace the main tank 31 by informing the user. At this time, since the range of the normal ink storage amount is narrow, the width from the detection of an abnormality to the lower limit storage amount where normal ink supply to the inkjet head 211 is actually difficult is set to the sub tank 251. Therefore, it is possible to prompt the user to replace the main tank 31 with a margin.

In addition, the control unit 40 prohibits ink ejection from the inkjet head 211 as an abnormality handling operation when the lower limit sensor 251b does not detect the lower limit storage amount of ink. That is, it is possible to provide a delay after the ink supply abnormality is detected by the reference sensor 251a until it is necessary to actually prohibit the ink discharge operation by the inkjet head 211. Therefore, even when the main tank 31 runs out of ink, image formation is possible. The user can replace the main tank 31 with a margin without interrupting the operation, and can restart and continue the ink supply.

Further, the lower limit storage amount is set to be equal to or larger than the maximum ink amount necessary for forming the image in the maximum range that can be set as the image formed by the inkjet head 211, and the control unit 40 determines that the lower limit sensor 251b has the lower limit storage amount. After forming an image in the middle of formation at the timing when ink is no longer detected, ink ejection from the inkjet head 211 is prohibited before starting the formation of the next image. In other words, when the main tank 31 is out of ink, it is possible to prompt the user to replace the main tank 31 before normal ink supply to the inkjet head 211 becomes impossible. Even if the ink storage amount in the sub tank 251 falls below the lower limit storage amount without being replaced, the ink ejection is stopped after the formation of the image that was being formed at that time is terminated. Do not waste recorded recording media and ink.

Further, the maximum ink feeding speed by the supply pump 32 is higher than the ink feeding speed by the liquid feeding pump 253 corresponding to the maximum ink discharge amount from the ink jet head 211 during the operation of the ink jet head 211. Accordingly, even when the image forming operation is executed with the maximum capacity of the inkjet head 211, the ink supply from the main tank 31 to the sub tank 251 or the ink supply to the sub tank 251 after the replacement of the main tank 31 is performed. The amount of ink in the sub tank 251 can be reliably recovered to the standard storage amount.

Further, an intermediate tank 262 is provided between the liquid feed pump 253 and the inkjet head 211. Therefore, the ink pressurized and sent from the sub tank 251 by the liquid feed pump 253 can be easily and appropriately supplied to the inkjet head 211 by controlling the pressure regardless of the amount of ink stored in the sub tank 251. is there.

The control unit 40 operates the supply pump 32 when the reference sensor 251a does not detect the standard storage amount of ink, and counts the operation time of the supply pump 32 until the reference sensor detects the standard storage amount again. A continuation reference time for detecting an abnormality in supply from the main tank 31 to the sub-tank 251 is set based on the result of the counting one or more times.
In other words, the initial value is most surely set to the maximum time corresponding to the case where the ink discharge amount by the inkjet head 211 is the maximum as the continuation reference time, but the ink discharge is determined according to the actual image to be formed. Since the amounts are different, by setting a shorter continuation reference time based on the actually measured values corresponding to the different ink discharge amounts, it is possible to detect the ink supply abnormality more quickly and reliably and notify the user.

The present invention is not limited to the above-described embodiment, and various modifications can be made.
For example, in the above embodiment, as the abnormality handling operation, a predetermined notification operation that can be executed by the display screen of the operation display unit 42 or the notification operation unit 43 is performed, and the operation of each unit of the inkjet recording apparatus 100 or the inkjet head Although the operation of 211 is prohibited, various other operations such as transmission of an e-mail or a message via the communication unit 41 are possible.

In the above embodiment, the upper limit storage amount corresponding to 251c is set to a level that is not detected even if all the ink in the ink flow path (circulation flow path) returns to the upper limit sensor. May be a detected level. However, the capacity of the sub tank 251 is preferably larger than the sum of the standard storage amount and the ink capacity.

In the above embodiment, whether or not the operation of the supply pump 32 is determined in real time based on the detection result in real time by the reference sensor 251a, detection data is acquired at a predetermined detection interval, and according to the detection interval. The operation of the supply pump 32 may be switched at time steps. Alternatively, the detection result itself is acquired in real time, but it may be set to operate continuously for a predetermined time after the operation of the supply pump 32 is once switched. The detection interval and the predetermined time are sufficiently longer than the time required for the ink storage amount to change from the standard storage amount to the lower limit storage amount and the upper limit storage amount due to the liquid supply by the liquid supply pump 253 and the ink supply by the supply pump 32. Short.

In the above embodiment, the case where the initial value (fixed value) corresponding to the assumed maximum time and the updated value based on the actual measurement time are used as the predetermined continuation reference time has been described. However, it is linked to the operation state of the liquid feeding pump 253. You may change it.

Further, in the above embodiment, when the ink storage amount falls below the lower limit storage amount, the operation of the inkjet head 211 is immediately prohibited (stopped), and the operation is prohibited after the image is formed to a good place. In the case where the operation is immediately prohibited, the image formation is started from the position where the image formation is stopped after the supply of ink from the main tank 31 is resumed and the operation prohibition is released. May be restarted to complete the formation of the image to be formed.

In the above embodiment, the back pressure control is performed on the nozzles of the inkjet head 211 using the intermediate tank 262, but the back pressure control is not limited to this method.
In the above embodiment, the ink flow path is described as a circulation flow path, but the present invention can be applied even when there is no recovery flow path to be returned to the sub tank 251.

In the above embodiment, the main tank 31 is replaced as a whole container. However, the ink may be replenished by injecting ink into the container of the main tank 31.

In the above embodiment, the supply pump 32 is used as the first liquid feeding means for supplying ink from the main tank 31 to the sub tank 251. However, the present invention is not limited to this. As a relative arrangement that allows the ink in the main tank 31 to flow into the sub tank 251 by gravity, the ink supply valve provided in the ink flow path is controlled to be opened or closed to switch whether ink can be supplied to the sub tank 251 or not. May be.

In the above embodiment, the sub tank 251 has a capacity smaller than that of the main tank 31, but the present invention is not limited to this. The capacity of the sub-tank 251 may be larger than that of the main tank 31, and the possible time for image formation after the empty detection of the main tank 31 can be set longer, so that the replacement or replenishment of the main tank 31 has more margin. Can be performed.

Further, in the above-described embodiment, the ink jet recording apparatus provided with the line head that discharges each of a plurality of colors of inks has been described as an example. However, only a single color image formation may be used. An ink jet recording apparatus that coats a recording medium with the above ink is also included. The number and arrangement of nozzles in the inkjet head 211 and the number and arrangement of the plurality of inkjet heads 211 are arbitrary, and an image is formed on the recording medium while moving (scanning) the inkjet head 211 with respect to the recording medium. The present invention can also be applied to a scanning type ink jet recording apparatus.
In addition, specific details such as the configuration, arrangement, and control content shown in the above embodiment can be changed as appropriate without departing from the spirit of the present invention.

The present invention can be used for an ink jet recording apparatus.

DESCRIPTION OF SYMBOLS 100 Inkjet recording apparatus 10 Conveying part 11 Driving roller 12 Conveying motor 14 Conveying belt 20 Image forming part 211 Inkjet head 22 Carriage 23 Carriage elevating part 231 Motor driver 232 Elevating motor 233 Electromagnetic brake 234 Beam member 235 Support part 24 Head driving part 251 Sub tank 251a Reference sensor 251b Lower limit sensor 251c Upper limit sensor 252 Flowmeter 253 Liquid feed pump 254 Filter 255 Deaeration module 256 Liquid common flow path 257 Individual flow path 258 Individual supply valve 259 Damper 260 Intermediate tank flow path 261 Intermediate tank flow valve 262 Intermediate Tank 262a Middle upper limit sensor 262b Middle reference sensor 263 Common supply valve 265 Maintenance flow path 66 Maintenance flow channel distribution valve 27 Recovery flow channel 270 Bypass valve 271 Check valve 272 Recovery common flow channel 273 Recovery valve 274 Circulation valve 275 Recovery pumps 281 to 283 Check valve 29 Suction part 291 Check valve 292 Chamber 292a Liquid quantity sensor 293 Vacuum pump 294 Pressure sensor 30 Ink reservoir 31 Main tank 32 Supply pump 35 Rack 40 Controller 401 CPU
402 RAM
403 ROM
403a Supply time history data 403b Notification reference time 404 Memory 41 Communication unit 42 Operation display unit 43 Notification operation unit 49 Bus

Claims

A recording head for ejecting ink;
A first tank for storing ink;
A second tank for storing ink supplied from the first tank;
First liquid feeding means for feeding ink from the first tank to the second tank;
One or a plurality of second liquid feeding means for feeding ink from the second tank to the recording head;
A reference sensor for determining whether or not a predetermined standard storage amount of ink is stored in the second tank;
An upper limit sensor for determining whether or not an upper limit storage amount larger than the standard storage amount is stored in the second tank;
A lower limit sensor for determining whether or not a lower storage amount of ink smaller than the standard storage amount is stored in the second tank;
A control unit;
With
The controller is
According to the detection result of the reference sensor, the presence or absence of operation of the first liquid feeding means is determined,
An ink jet recording apparatus that performs a predetermined abnormality handling operation according to detection results of the upper limit sensor and the lower limit sensor.
A recovery flow path for returning ink from the recording head to the second tank;
The difference between the upper limit storage amount and the standard storage amount is larger than the ink capacity of the ink flow path from the time when the second storage tank is sent to the time when the second storage tank returns to the second tank. Inkjet recording apparatus.
A notification unit for performing a predetermined notification operation;
The control unit operates the first liquid feeding means when the reference sensor does not detect the standard storage amount of ink, and operates the first liquid feeding means for a predetermined continuous reference time or more. The inkjet recording apparatus according to claim 1, wherein when the reference sensor does not detect the standard storage amount of ink, the notification unit performs a notification operation.
4. The control unit according to claim 1, wherein when the lower limit sensor does not detect the lower limit storage amount of ink, the control unit prohibits ink ejection from the recording head as the abnormality handling operation. The inkjet recording apparatus according to Item.
The lower limit storage amount is determined to be equal to or greater than the maximum ink amount necessary for forming an image in the maximum range that can be set as an image formed by the recording head,
The control unit prohibits ink ejection from the recording head after forming an image in the middle of formation at a timing when the lower limit sensor no longer detects the lower limit storage amount of ink and before starting to form the next image. The inkjet recording apparatus according to any one of claims 1 to 3, wherein:
The maximum ink feeding speed by the first liquid feeding means is higher than the ink feeding speed by the second liquid feeding means according to the maximum ink discharge amount from the recording head during operation of the recording head. 6. The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus is large.
7. The ink jet recording apparatus according to claim 1, wherein a third tank is provided between the second liquid feeding means and the recording head.
The control unit operates the first liquid feeding means when the reference sensor does not detect the standard storage amount of ink, and the first sensor until the reference sensor detects the standard storage amount again. 4. The ink jet recording apparatus according to claim 3, wherein the operation time of the liquid feeding means is counted, and the predetermined continuation reference time is set based on a result of one or more times of the counting.